







                ***********************************
                *                                 *
                *        COURIER V.34 Manual      *
                *                                 *
                ***********************************




               Copyright 1994 by U.S. Robotics, Inc.

U.S. Robotics, the U.S. Robotics logo, and HST are registered trademarks 
of U.S. Robotics, Inc.  Courier HST Dual Standard Fax, Courier V.32 terbo 
Fax, Total Control, and Adaptive Speed Leveling (ASL) are trademarks of 
U.S. Robotics, Inc.  V.Fast Class and V.FC are trademarks of Rockwell 
International.  Any trademarks, tradenames, service marks or service names 
owned or registered by any other company and used in this manual are the 
property of their respective companies.


*****************************************************************************
TABLE OF CONTENTS
*****************************************************************************

How to Use this Manual
Table of Contents   
Limited Warranty      
FCC Registration Numbers  
IC (Industry Canada)   
Connecting to the Telephone Company     
Radio and Television Interference       
For Canadian Modem Users      


PART I.  INSTALLATION AND OPERATION

Chapter 1--Features and Compatibility
Introduction   
Features       
Compatibility  
  Fax Standards 
  Other Compatibility Features 

Chapter 2--External Modem Set Up 
Switches on the Modem  
Front Panel Indicators on the Modem  
Package Components     
What You Need 
  An RS-232 Cable 
  Communications Software. . . 
  Telephone Adapter. . . 
You Should. . .
  Refer to Appendix F. . .  
  Refer to Appendix G. . .  
Installing the Modem   
Testing the Installation 

Chapter 3--Internal Modem Set Up
Package Components    
What You Need  
  Communications Software. . . 
  A Telephone Adapter     
You Should. . . 
  Refer to Appendix F. . .       
  Refer to Appendix G. . .   
Before Installing the Modem     
  Select a Serial Port   
  Select an Interrupt Request (IRQ)      
  Reset the Jumpers     
  Set DIP Switches       
Installing the Modem    
Testing the Installation       

Chapter 4--Data Mode Command Summary
Command Set Usage     
Basic Commands 
Dialing/Answering     
  Dialing         
  Dial Options    
  Cancel Dialing 
  Store Phone Numbers    
  Redialing      
  Answer Mode     
  Hanging Up      
Setting/Using Defaults 
  Customizing NVRAM      
  Resetting the Modem    
Configuration  
  Echo/Speaker    
  Result Codes   
  Additional Result Code Sets   
  Modulation      
  Error Control/Data Compression  
  Data Rates      
  RS-232 Signal Operations       
  Flow Control   
S-Registers    
Inquiry and Help      
Testing
International Calls 
Miscellaneous Commands 

Chapter 5--Fax Operations and Call Detection 
Fax Operations  
Notes to Programmers   
Call Detection 

Chapter 6--Queries and Help Screens       
User Inquiries      
S-Register Query  
Phone Number Query       
Last-Dialed Number Inquiry      
Stored Command String Query      
Help Screens   
    Stop/Restart Display  
    Cancel Display  
  Basic Command Set   
  Extended Command Set     
  Dialing    
  S-Register Functions     
  Percent Commands 


PART II. REFERENCE

Appendix A--Link Negotiation (Handshaking) and Error Control       
V.34 Handshaking       
V.Fast Class (V.FC) Handshaking 
U.S. Robotics V.32 terbo to U.S. Robotics V.32 terbo   
Other V. Protocol Operations   
  Dual Standard Handshaking      
Error Control and Throughput   
  V.42 Handshaking        
  MNP Handshaking
  Data Compression       
  Flow Control   
  Throughput Guidelines  
    Typical Throughput     

Appendix B--Summaries and Tables  
The RS-232 Interface  
Front Panel Indicators  
DIP Switch Summary      
Default Settings         
  Factory Templates
    &F1 Hardware Flow Control (Default)  
    &F2 Software Flow Control       
    &F3 HST Cellular       
    &F0 No Flow Control    
  NVRAM Options  
S-Register Summary    
ASCII Chart    

Appendix C--Alphabetical Command Summary 
Command Set Usage   
Basic Command Set       
Ampersand (&) Command Set      
Percent (%) Command Sets        

Appendix D--Dial Security/Remote Access   
Dial Security  
Remote Access  

Appendix E--Troubleshooting       

Appendix F--Synchronous and Leased Line Operations
Synchronous   
  V.25 bis       
  Online synchronous   
Dedicated Line and Leased Line Operations     

Appendix G--Additional Operations 
Cellular Operations     
Voice/Data (External Modems Only)   
Hewlett Packard 3000 Installations     
MI/MIC Operations (External Modems Only)       
 
Appendix H--Modem Testing 
Testing with &T 
  Ending a Test--&T0, S18  
  Analog Loopback--&T1, &T8 
  &T2    
  Digital Loopback--&T3    
  &T4, &T5      
  Remote Digital Loopback--&T6, &T7 
Testing with Register S16       
  Analog Loopback--S16=1D  
  Dial Test--S16=2  
  Test Pattern--S16=4      
  Remote Digital Loopback--S16=8   

Appendix I--Software Upgrades     

Appendix J--Glossary      

Appendix K--Technical Specifications      

Index

  

**********************
HOW TO USE THIS MANUAL
This manual contains operating instructions for Courier Dual Standard 
V.34 and Courier V.34 modems.  These modems have many similar features 
except for the signaling they use to connect with remote modems at high 
speeds:  V.32/V.32 terbo, HST, V.FC, or V.34.  Courier HST Dual Standard 
modems use any type of signaling, depending on the type of remote modem.  
V.34 modems can connect at rates up to 28.8K bps.

Below is a brief description of the manual's contents.

* Chapter 1--Operating and Compatibility Features
* Chapter 2--Installation 
* Chapter 3--Internal Modem Installation
* Chapter 4--Data Mode Commands
* Chapter 5--Fax Mode and Call Selection
* Chapter 6--Queries and Help commands to display current settings, 
  operational summaries, and other data
* Background information on protocols, error control, and throughput
* Summaries and tables
* Alphabetical Command Summary
* Dial Security operations
* Troubleshooting
* Online synchronous and V.25 bis synchronous operations
* Additional features such as HST Cellular and voice/data switch 
* Procedures for modem testing
* Procedures for upgrading your modem via software downloads
* Glossary
* Warranty/Service/Certification information

*********************************
A Note on Communications Software

If you're using a computer rather than a terminal, you need communications 
software.  Many brands are available, all of which are based on the modem's 
AT command set. Some users prefer their communications software to take 
control of the modem, and are more comfortable with a program that makes 
the modem almost transparent.   Others prefer a program that allows them to 
use the modem's AT command set sometimes, and their software at other times, 
depending on the task at hand.  Review at least Chapter 4 so that you have a 
basic understanding of the modem's requirements and operation. 

****************
LIMITED WARRANTY
U.S. Robotics, Inc., warrants to the original consumer or other end user 
purchaser that this product is free from defects in materials or workmanship 
for a period of two years from the date of purchase.  During the warranty 
period, and upon proof of purchase, the product will be repaired or replaced 
(with the same or similar model) at our option, without charge for either 
parts or labor.  This warranty shall not apply if the product is modified, 
tampered with, misused, or subjected to abnormal working conditions.
REPAIR OR REPLACEMENT AS PROVIDED UNDER THIS WARRANTY IS THE EXCLUSIVE 
REMEDY OF THE PURCHASER.  THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, 
EXPRESS OR IMPLIED, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR 
FITNESS FOR A PARTICULAR USE OR PURPOSE, AND U.S. ROBOTICS SHALL IN NO EVENT 
BE LIABLE TO PURCHASER FOR INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND OR 
CHARACTER.

Some states do not allow the exclusion or limitation of incidental or 
consequential damages or allow limitations on how long an implied warranty 
lasts, so the above limitations or exclusion may not apply to you.  This 
warranty gives you specific legal rights.  You may also have other rights 
which vary from state to state.

Should you encounter problems in operating this device, follow the 
instructions in Appendix E in Part II of this manual.  The appendix contains 
solutions to operating problems as well as procedures to follow if there is 
an apparent modem malfunction.

****************
FCC REGISTRATION
       FCC68:  CJEUSA-73130-FA-E
       RINGER EQUIVALENCE:  0.4B
       FCC15:  
             CJE-0263 (External modem)
             CJE-0269 (Internal modem)
             CJE-158-243 (Motherboard)
             CJE-0151-243 (Daughterboard)

********************
IC (Industry Canada)
This digital apparatus does not exceed the Class B limits for radio noise 
emissions from digital apparatus set out in the radio interference 
regulations of Industry Canada (formerly Canadian Department of 
Communications).

Le present appareil numerique n'emet pas de bruits radio-electriques 
depassant les limites applicables aux appareils numeriques de la classe 
B prescrites dans le Reglement sur le brouillage radioelectrique edicte 
par le ministere des Communications du Canada.

***********************************
Connecting to the Telephone Company
It is not necessary to notify the telephone company before installing 
the modem.  However, the telephone company may request the telephone 
number(s) to which the Courier is connected and the FCC information 
printed above.

If the modem is malfunctioning, it may affect the telephone lines.  In this 
case, disconnect the modem until the source of the difficulty is traced.  
Do not use the modem on party or coin telephone lines.

*********************************
Radio and Television Interference
This equipment generates and uses radio frequency energy, and, if not 
installed and used properly in strict accordance with the  manufacturer's 
instructions, may cause interference to radio and television reception.  
Courier high speed modems have been tested and found to comply with the 
limits for a Class B computing device in accordance with the specifications 
in Part 15 of FCC rules, which are designed to provide reasonable protection 
against such interference in a residential installation.

However, there is no guarantee that interference will not occur in a 
particular installation.  If this device does cause interference to radio 
or television reception, which you can determine by monitoring reception 
when the modem is on and off, try to correct the problem with one or more 
of the following measures.

*  Reorient the receiving antenna.
*  Relocate the computer with respect to the receiver.
*  Relocate the computer and/or the receiver so that they are on separate 
   branch circuits.

If necessary, consult your dealer or an experienced radio/ television 
technician for additional suggestions.  You may find the following booklet, 
prepared by the Federal Communications Commission, helpful:

How to Identify and Resolve Radio-TV Interference Problems
Stock No. 004-000-0345-4
U.S. Government Printing Office
Washington, DC 20402

In accordance with Part 15 of the FCC rules, any modification to or 
tampering with this device that causes harmful interference to others may 
be reason for prohibiting future operation.

************************
For Canadian Modem Users
The Industry Canada (formerly DOC) label identifies certified equipment.  
This certification means that the equipment meets certain telecommunications 
network protective, operational, and safety requirements.  The department 
does not guarantee the equipment will operate to a user's satisfaction.
Before installing this equipment, make sure you are permitted to connect it 
to the facilities of the local telecommunications company.  You must also 
install the equipment using an acceptable method of connection.  In some 
cases, you may also extend the company's inside wiring for single line 
individual service by means of a certified connector assembly (telephone 
extension cord).  You should be aware, however, that compliance with the 
above conditions may not prevent degradation of service in some situations.
Repairs to certified equipment should be made by an authorized Canadian 
maintenance facility designated by the supplier.  Any repairs or alterations 
made by a user to this equipment, or equipment malfunctions, may give the 
telecommunications company cause to request the user to disconnect the 
equipment.

For your own protection, make sure that the electrical ground connections 
of the power utility, telephone lines, and internal metallic water pipe 
system, if present, are connected together.  This precaution may be 
particularly important in rural areas.

WARNING:  Do not attempt to make such connections yourself; contact the 
appropriate electric inspection authority or electrician.

Courier High Speed Modems Load Number:  5

The Load Number (LN) assigned to each terminal device denotes the 
percentage of the total load to be connected to the telephone loop used 
by the device, without overloading.  The  termination on a loop may consist 
of any combination of devices, subject only to the requirement that the 
total of the Load Numbers of all the devices not exceed 100.  


Chapter One--Features and Compatibility

************
INTRODUCTION
Congratulations!  The Courier modem you've purchased represents powerful, 
advanced electronic design that offers exceptional reliability, 
compatibility and flexibility at all standard rates up to 28,800 or 
28.8K bits per second (bps).  The transmission rate between the computer 
and modem, depending on your equipment and software support, can be as 
high as 115.2K bps.

********
Features
The following features and capabilities assure you of superior reliability 
and performance.

Connections up to 28.8K bps
With the V.34 standard and the V.Fast Class modulation scheme, two modems 
can connect at rates up to 28.8K bps, twice as fast as the rates of standard 
ITU-T (formerly CCITT) V.32 bis modems, which are limited to calls of 14.4K 
bps or less.

Software Upgrades
Courier high speed modems are now software upgradable, allowing you quick, 
easy access to the latest advances in data communication technology.  See 
Appendix I.

Quick Connect
In V.32 terbo mode, Courier high speed modems can handshake and start 
transmitting much faster than typical training times that range between 
9 and 18 seconds for other modems.

Universal Connect
Courier high speed modems automatically detect and connect at the fastest 
available speed.

Adaptive Speed Leveling (ASL)
Like most high speed modems, Courier modems fall back to the next lower 
speed—for example, 19.2K, then 16.8K in V.terbo mode--if poor line conditions 
warrant.  In addition, Courier V.32 bis, and V.32 terbo modems detect 
improved line conditions and shift upward again to the next higher speed.  
Both transmit and receive channels adapt independently, each detecting and 
adjusting to line conditions.  ASL keeps the modems online, always operating 
at the highest possible speed, and constantly ensuring data integrity.

Fax Capability
You can use your modem with Class 1 or Class 2.0 facsimile software to 
exchange faxes with millions of Group III fax machines worldwide.  See 
Chapter 5.

Error Control--V.42/MNP
Data integrity is ensured when the modems connect with remote modems that 
use the V.42 (LAPM), HST, or MNP error control protocols.  Error control is 
available on calls at 1200 bps and above.

Data Compression--V.42 bis/MNP5
Data compression enables potential throughput of up to 115.2K bps on 28.8K  
bps connections.  Couriers connecting under V.42 or HST error control use 
V.42 bis compression.  Couriers connecting under MNP error control use 
MNP Level 5 compression.  Typical throughput of text and other types of 
files using V.42 bis is provided in Appendix A.  

Flow Control/Variable Serial Port Rates 
Flow control, required under error control, also allows the local serial 
port (DTE) rate to be set higher than the link (connection) rate, enabling 
greater efficiency and throughput.  If your equipment and software support 
high rates, data can be sent from the computer to the modem at 115.2K, 
57.6K, 38.4K or 19.2K bps, regardless of the link rate.

Voice/Data Switch
A switch on the modem's front panel allows you to change from voice to data 
and back again, without issuing a command.  See Appendix G.

Stored Command String
If you don't ordinarily use voice and data in the same call, you can assign 
the voice/data switch a different function that normally requires a command, 
such as resetting the modem or executing a stored command string.  See 
Voice/Data in Appendix G for instructions on use of the voice/data switch. 

Asynchronous/Synchronous Capability 
Courier high speed modems operate synchronously as well as asynchronously.  
A personal computer equipped with a synchronous interface adapter can call 
computers that use standard synchronous protocols.  See Appendix F for more 
information.

Synchronous Operations with V.25 bis
Used with computers that have a synchronous card and port, Courier high speed 
modems combine the power of older modems and automatic calling units in the 
mainframe environment.  They make synchronous connections by utilizing V.25 
bis, character-oriented (similar to BISYNC) and HDLC protocols.  See 
Appendix F for more information.

Dial Security
With Dial Security, you will be able to prevent unauthorized access to a 
system with the use of Autopass, Prompting, and Dialback.  See Appendix D 
for more information.

Programmable Nonvolatile Memory
You can tailor your own default settings and store them in nonvolatile 
random access memory (NVRAM).  Each time the Courier is powered on or reset, 
it operates at the settings you've specified.  See Chapter 4, Appendix B, 
and Appendix C.

Link Rate Negotiation
The Courier automatically lowers its link rate to match a lower rate of a 
remote modem, in both Originate and Answer Modes, allowing connections with 
a wide range of installed modems.

Link Diagnostics
After each call, you can display a Link Diagnostics screen containing 
information about the last call, including the number of data characters 
transferred, line statistics, the call's rate and the reason the call was 
disconnected.  See Chapter 6.

Modem Diagnostics
ITU-T V.54 loopback testing with the &T command options, and earlier Courier 
Register S16 test options are available.  The modem performs three loopback 
tests:  analog, digital, and remote digital.  See Appendix H for information.

Inactivity Timer
You can set the modem to automatically hang up after a specified number of 
minutes if there is no activity on the phone line.  See Register S19 in 
Appendix B.

Call Duration Reporting
The modem records the duration of your calls in hours, minutes, and seconds.  
This feature enables you to display and print an audit of your calling 
activities.  You can optionally use the modem clock as a real-time clock.  
See the I3 and I6 screens in Chapter 6 and the K command in Chapter 4 and 
Appendix C.

Call Progress Detection
An optional set of result codes (screen messages) lets you know when a 
line is busy, a person rather than a modem has answered the phone, there 
is no dial tone, or the distant phone is ringing.

Modem Settings Displays
On command, the modem displays its current settings, a handy way to check 
your transmission rate, S-Registers and other operational controls.  The 
modem also displays the defaults stored in nonvolatile memory as well as 
its default configuration templates.  See Chapter 6.

HELP Screens
The modem displays screens that summarize the command sets, Dial command 
options, and S-Register functions.  See Chapter 6.

Bottom Panel Reference
Command summaries and other information are printed on the bottom of the 
modem case.  A Dual In-Line Package (DIP) switch guide makes it easy to 
tailor the switch settings to your terminal or software requirements. 

Dialing the Last-Dialed Number
The modem has a buffer that stores each dialed number until it is cleared 
by another Dial command.  A few keystrokes cause the modem to redial the 
number in the buffer without your having to enter the number again.  See 
the DL command in Appendix C.

Automated Redialing 
You can put the modem into Repeat Mode to continuously redial if a previous 
dial attempt fails to connect.  This is especially useful in dialing 
services whose lines are often busy.  See Chapter 4.

Quote Mode
Set the modem to Quote Mode if you want it to dial an alphabetic acronym 
instead of a numeric number.  See Chapter 4.

*************
COMPATIBILITY
The Courier adheres to the following modulation schemes and standards, 
ensuring compatibility with a wide base of installed modems.  Unless 
otherwise indicated, Dual Standard V.34 modems conform to the listed 
standards.

NOTE:  The International Telecommunication Union (ITU-T) was formerly the 
International Telegraph and Telephone Consultative Committee (CCITT).

ITU-T V.34      28.8K/26.4K/24K/21.6K/19.2K/16.8K/14.4K/12K/ 
                9600/7200/4800/2400 bps
V.FC            28.8K/26.4K/24K/21.6K/19.2K/16.8K/14.4K bps
V.32 terbo      21.6K/19.2K/16.8K/14.4K/12K/9600/
7200/4800 bps 
HST             16.8K/14.4K/12K/9600/7200/4800 bps (Dual Standard modems 
                in HST mode with ASL up to 21.6K bps)
HST Cellular    Cellular connections at 12K/9600/7200/ 4800/2400/1200/300 bps  
                (Dual Standard modems in HST mode)
ITU-T V.32 bis  14.4K/12K/9600/7200/4800 bps
ITU-T V.32      9600/4800 bps 
ITU-T V.22 bis  2400 bps
Bell 212A       1200 bps (also V.22)
ITU-T V.23      1200 bps with 75 bps back channel (some U.K. and European 
                phone systems)
ITU-T V.25      Answer sequence for calls originating outside the U.S. and 
                Canada
ITU-T V.25 bis  For synchronous communications using HDLC and character-
                oriented protocols
Bell 103        300 bps (ITU-T V.21 optional)
ITU-T V.42      LAPM error control, 1200 bps and higher
ITU-T V.42 bis  Data compression, 1200 bps and higher
MNP             Levels 2, 3 and 4 error control, level 5 data compression, 
                1200 bps and higher
ITU-T V.54      Analog, digital and remote digital loopback testing

*************
Fax Standards
The Courier modem provides Group III-compatibility when combined with Class 
1 or Class 2.0 fax software.  In addition, the modem adheres to the following 
standards.

TIA/EIA-578      Service Class 1 Asynchronous Facsimile DCE Control Standard
TIA/EIA-592      Service Class 2.0 Asynchronous Facsimile DCE Control Standard
ITU-T V.17       14.4K/12K bps
ITU-T V.29       9600/7200 bps
ITU-T V.27 ter   4800/2400 bps
ITU-T V.21       300 bps

****************************
Other Compatibility Features
Other compatibility features include the following standards and 
certification:

*  Can be used with any computer or terminal that is compatible with the 
   RS-232 standard interface.
*  Can be used with any computer or terminal that uses ASCII, the standard 
   character code supported by most equipment manufacturers.
*  Is fully FCC- and IC-certified for the uses described in this manual.  


Chapter 2--Modem Set Up

********
Reminder
To prevent overheating, do not cover the vents on the top of the modem case.

*********************
Switches on the Modem

Voice/Data
This push-button switch is used primarily to switch between voice and data 
communications during a call.  Detailed instructions are in the Voice/Data 
Calls section in Appendix G.  

Volume Control
This is a slide switch underneath the right side panel of the modem, near 
the front corner.  Sliding it toward the front of the modem increases the 
modem speaker's volume; sliding it toward the rear of the modem decreases 
the volume.

Front Panel Indicators on the Modem
The modem has twelve status lights, or LEDs.  See Appendix B for descriptions 
of their operations.

PACKAGE components
Your Courier modem package contains the following items:
*  The modem you purchased:  Courier V.34
*  An RJ11C phone cord
*  A power adapter
*  Fax software and manual
*  A Quick-Reference card

*************
What You Need
The Courier modem has minimal operational requirements.  Be sure to read the 
information in the front of this manual about radio and television 
interference and connecting to the phone company.  In addition, you should 
be aware of the following requirements.

An RS-232 Cable
You need an RS-232 cable to connect the modem to your computer or terminal.  
Use a shielded cable to ensure minimal interference with radio and 
television reception.  

NOTES:  
*  Refer to Appendix B for a listing of RS-232 pin assignments required to 
   operate the modem.  Be sure to check the appendix if you're not sure what 
   type of cable you need, or if you're building your own.  
*  If your machine has other than a 25- or 9-pin port, check your computer 
   documentation or consult your dealer to find out what type of RS-232 
   connector is required. 

WARNING:  If you're planning to use the high speed computer-to-modem rates 
of 115.K, 57.6K or 38.4K bps, follow the instructions concerning the RS-232 
cable in Appendix B.  The guidelines there will help you to avoid signal 
degradation at very high speeds. 

Communications Software. . .   
. . .if the modem is attached to a computer instead of a terminal.
The software uses the modem's AT command set to control many communications 
functions, including configuring the modem, dialing, and answering calls, and 
also enables the transfer of files and other operations.

Some users prefer their communications software to take control of the 
modem, and are more comfortable with a program that makes the modem almost 
transparent.   Others prefer a program that allows them to use the modem's 
AT command set sometimes, and their software at other times, depending on 
the task at hand. 

Review Chapter 4 so that you have a basic understanding of the modem's 
requirements and operation. 

Telephone Adapter. . . 
. . .if you have an older telephone installation that does not have the 
appropriate modular wall jack and plug.  

Adapters and RJ11C connectors are available from your telephone company or 
computer dealer.

***************
You Should. . .

Refer to Appendix F. . . 
. . .if your phone line is user-installed or if it is leased from the 
telephone company.

Refer to Appendix G. . .
. . . if your modem is installed in a Hewlett Packard system that uses the 
Ack/Enq communications protocol.

********************
Installing the Modem 

1. Turn off the computer or terminal and its peripheral devices.

2. Examine the label on the bottom of the modem.  In addition to the 
   summaries and other information, the label contains icons to aid in 
   modem installation.

3. Make sure that the modem's power switch is OFF; press it towards the zero 
   in the 0/1 icon on the bottom label.  

4. Plug the power supply adapter's small connector into the power jack at 
   the back of the modem.  Plug the adapter into a standard 115-volt AC 
   wall socket.

5. Disconnect your present phone cable from the wall jack.  Plug one end of 
   the supplied phone cable into the modem's phone jack (refer to the bottom 
   label).  Plug the other end into the wall jack.

   If you want to keep your telephone connected for conventional calls, plug 
   its cord into the modem's telephone jack (refer to the bottom label). 

6. Check the positions of the bank of Dual In-Line Package (DIP) Switches 
   located in the well at the bottom of the modem.  These switches are set 
   at the factory to the positions most users require.  

   Check your software documentation for its requirements, particularly for 
   DIP switches 1, 4, 5 and 6.  You'll also find descriptions of switch 
   functions and options in Appendix B.

   NOTE:  If you have built your own RS-232 cable and it does not support the 
   Data Terminal Ready (DTR) signal, set DIP switch 1 ON, for DTR override.  
   The override causes the modem to operate as if the DTR signal were always 
   ON, and enables the modem to accept commands.  Most purchased communications 
   software, however, requires normal DTR.

7. The final step is to connect the modem to the computer's or terminal's 
   serial port with the RS-232 cable.  Attach the appropriate connectors to 
   the modem and to the serial port.

************************
Testing the Installation

Use the following procedures to verify that your modem is working properly.

1. Turn on your computer or terminal.  Then turn the Courier's power switch 
   ON.  The following front panel indicators, or LEDs, will light up on the 
   modem. 
      
      CD   Carrier Detect, if you have set DIP switch 6 ON, enabling the 
	   CD override
      TR   Data Terminal Ready, if you have set DIP switch 1 ON, enabling 
	   the DTR override
      MR   Modem Ready/Power ON
      CS   Clear to Send

2. If you're using a personal computer, load your software to start the 
   program.  Set your terminal or software to 19.2K bps or 9600 bps.  
   In addition, set a word length of either 7 bits plus 1 parity bit, or 
   8 bits with no parity—it doesn't matter which at this time—and 1 Stop bit.  
   Set the software to use the correct serial port (port through which the 
   modem connects to the computer).

3. Perform the function that lets you send AT commands to the modem, that is, 
   puts the computer in Terminal mode.  Some communications programs do 
   this automatically upon loading.  Others require you to display a 
   communications or terminal screen, type a Function key, or perform some 
   other operation.

   Review your communications software documentation for instructions. 
   
4. Send the following attention command.  Type either upper or lower case 
   letters, not a combination, and then press the Enter (Carriage Return) 
   key, shown in the example below between angle brackets.  (Don't type the 
   angle brackets.)

       AT <Enter>

  If everything is correct, the modem responds as follows:

       OK

   Go on to step 5.

   Troubleshooting
   If your entered command is not displayed, your local echo is OFF.  To 
   turn the local echo ON, send the modem the following command:  
      
      ATE1 <Enter>
   
   If double characters appear on the screen, both your modem and software 
   are set to local echo ON.  Either set your software to local echo OFF, 
   or turn the modem's echo OFF with the following command:
      
      ATE0 <Enter>

   If no OK appears on your screen after you completed Step 4, review the 
   following checkpoints:

   a. Make sure you type all upper or lower case letters and press <Enter>.
   b. Check to see that you set your communications software to the correct 
      serial port.  The correct serial port is the port through which the 
      modem is connected to the computer.
   c. Make sure your software has put the computer in Terminal mode, so that 
      you can send the modem commands.  Then review Step 4, on the previous 
      page.
   d. Be sure that DIP switches 1 and 6 are set ON or OFF according to your 
      terminal or software requirements.  The table in Appendix B explains 
      each function, and you may also need to review your terminal or 
      communications software documentation.
   e. If you set DIP switch 8 OFF, for Dumb mode, reset the modem to Smart 
      mode:  set DIP switch 8 to ON.
   f. The modem is shipped with DIP switch 3 ON, enabling the result codes.  
   
      If DIP switch 3 is OFF, set it to the ON position.  Then initiate the 
      new switch setting with the following reset command:
       
	  ATZ <Enter>

5. As a final check, make sure the modem gets a dial tone.  Type the 
   following Dial command:
       
       ATD <Enter>

   On receipt of the command, the modem goes off hook and waits for a dial 
   tone.  The OH indicator lights up, and you'll hear the dial tone from 
   the modem's speaker.  To cancel the operation, press any key.

   Troubleshooting
   If you don't hear the dial tone, first increase the volume by sliding the 
   volume control switch towards the front of the modem.  If that doesn't 
   work, check to see that the phone cable from the wall jack is connected to 
   the correct jack on the modem (See Figure 2.3).  If necessary, reconnect 
   the phone cable correctly.  Then try the Dial command again, ATD <Enter>.

Chapter Three--Internal Modem Set Up

******************
Package Components

Your Courier modem package contains the following items:
*  The modem you purchased:  Courier V.34
*  An RJ11C phone cord
*  A power adapter
*  Fax software and manual
*  A Quick-Reference card

************
What You Need
The Courier modem has minimal operational requirements.  Be sure to read 
the information in the front of this manual about radio and television 
interference and connecting to the phone company.  In addition, you should 
be aware of the following requirements.

Communications Software. . .   
. . .if the modem is attached to a computer instead of a terminal.
The software uses the modem's AT command set to control many communications 
functions, including configuring the modem, dialing, and answering calls, 
and also enables the transfer of files and other operations.

Some users prefer their communications software to take control of the 
modem, and are more comfortable with a program that makes the modem almost 
transparent.   Others prefer a program that allows them to use the modem's 
AT command set sometimes, and their software at other times, depending on 
the task at hand. 

Review Chapter 4 so that you have a basic understanding of the modem's 
requirements and operation. 

A Telephone Adapter. . . 
. . .if you have an older telephone installation that does not have the 
appropriate modular wall jack and plug.  

Adapters and RJ11C connectors are available from your telephone company or 
computer dealer.

***************
You Should. . .

Refer to Appendix F. . . 
. . .if your phone line is user-installed or if it is leased from the 
telephone company.

Refer to Appendix G. . .
. . . if your modem is installed in a Hewlett Packard system that uses the 
Ack/Enq communications protocol.


***************************
BEFORE INSTALLING THE MODEM

A typical new modem user has a PC with a printer connected to the PC's 
parallel printer port, and a mouse cable attached to the PC's first 
serial port.  For this user, the modem is the only device that requires 
a second serial port.  If this is your situation, you can skip this 
entire section except for DIP Switches, just before Installing the Modem.  
Just remember that after you load your communications software, you'll 
have to set the software to use the COM2 serial port.

IBM PC-compatible serial ports are referred to as COM ports.  Two COM ports 
are standard:  COM1 and COM2.  DOS recognizes up to four COM ports, although 
more can be programmed.  The Courier is set at the factory to use COM2.  
This is because many computers are shipped with COM1 equipped with an 
external serial connector for attaching a device such as a serial printer 
or serial mouse.  If you have one or more of these devices, you're probably 
already familiar with COM ports on a PC.

If you're only using COM1 for a device, you can skip this section except 
for DIP Switches, just before Installing the Modem.  If you've already 
installed devices at both COM1 and COM2, you will have to select either 
COM3 or COM4.  Carefully review the following section for complete 
instructions.

********************
Select a Serial Port
WARNING:  If you are going to use COM1, COM3, or COM4, you must change some 
switches on the modem board, called jumpers.  First, you need to select the 
correct Interrupt Request (IRQ) to use at that serial port.  Peripheral 
devices use IRQs to instruct the computer to stop the processor's current 
operation; this allows the devices to perform their operations.

Using COM1, 2, 3 or 4 depends on your equipment's configuration, as 
described below.  Remember which serial port you assign to the modem, 
because you must specify it to your
communications software later.  
The table in the next section includes hexadecimal addresses, required 
by some software.

COM1:        You may use this port if the computer does not have an installed 
	     serial connector at COM1.  (This situation is unlikely.)  You 
	     will have to modify some switches on the modem, so be sure to 
	     read this entire section of the chapter.  However, you may prefer 
	     to leave the modem set to COM2 and proceed to DIP Switches, just 
	     before the installation instructions.

COM2:        If your computer is equipped with one serial connector at COM1, 
	     and if you are not already using COM2 for another device, use 
	     this port.  (This is the most common configuration.)  Since the 
	     modem is already set to operate at COM2, skip the rest of this
	     section and proceed to DIP Switches, just before the installation
	     instructions.

COM3, COM4:  If you have two serial devices that already use COM1 and COM2, 
	     you can set the modem for either COM3 or COM4.  Review your 
	     communications software documentation to be sure your program 
	     supports these additional serial ports.  (Most programs do.)  
	     If your software doesn't, you will have to remove one of the 
	     other devices.

*********************************
Select an Interrupt Request (IRQ)
IBM-compatible computers reserve IRQ4 for COM1 and IRQ3 for COM2, as shown 
below.  Some communication programs support reserved IRQs for two serial 
ports.

     Serial Port    IRQ     Serial Port Address (Hex)
	COM1        IRQ4        3F8-3FF
	COM2        IRQ3        2F8-2FF
	COM3        IRQ4*       3E8-3EF
	COM4        IRQ3*       2E8-2EF
  
*Select IRQ4 (COM3) or IRQ3 (COM4) only after reading the following 
 guidelines:

If you need to use COM3 or COM4, keep the following in mind:

*  The Courier supports three additional IRQs:  IRQ2, IRQ5 and IRQ7.  
   Your software must support the one you use for COM3 or COM4.  However, 
   if your computer is XT-compatible, IRQ5 is reserved for the hard disk, 
   and it is not available for a serial port.  IRQ5 is available on 286-PCs 
   and higher.

*  Two devices should not use the same IRQ at the same time, because there 
   will be a conflict and you will probably lose data.  For example, if you 
   use IRQ4 for a mouse installed at COM1 and for your modem installed at 
   COM3 (as shown in the previous table) you cannot use the mouse and the 
   modem at the same time.
   
   Additionally, if an installed device doesn't use IRQs, you can use the 
   IRQ normally associated with that COM port.  For example, if you have a 
   serial printer at COM1 and you know it does not use an IRQ, you can use 
   IRQ4 at COM3.  Similarly, you could use IRQ3 at COM4 if the device at 
   COM2 doesn't use IRQ3.

If you cannot find the information you need in your software documentation, 
call your software's Technical Support Department for help in selecting an 
IRQ.  You may find it necessary to re-install your serial devices to 
correctly allocate the available serial ports and IRQs.

*****************
Reset the Jumpers
If you hold the modem so that the rear panel is at the bottom and the edge 
connector is at the left of the circuit board you can locate the COM and 
IRQ jumpers near the center left side of the board.

Each jumper has two upright contacts connected by a black plastic piece, 
called a shunt, placed over the contacts for the COM2 and IRQ3 settings.  
This shunt selects the jumper by closing the circuit.

To change a jumper setting, gently lift off the black shunt and replace it 
over the contacts you want.

As we've said, your choice of an IRQ for COM3 or COM4 depends on your 
hardware/software configuration.  If the device at COM1 or COM2 isn't 
using IRQ4 or IRQ3, you may use one of them.  Otherwise, check your PC 
and software documentation to see if you may use IRQ2, IRQ5 or IRQ7.

WARNING:  Do not select an IRQ position until you've read the previous 
guidelines and reviewed your software documentation. 

****************
Set DIP Switches
A ten-position bank of Dual In-Line Package (DIP) switches is located at 
the rear of the modem.  A summary of the DIP switch functions and options 
is in Appendix B in this manual and on the Quick Reference Card. 

WARNING:  Check your software documentation for its requirements, 
particularly for DIP switches 1, 4, 5 and 6. 

NOTE:  Once the modem is installed, the DIP switches are accessible 
through the computer's rear panel.

********************
Installing the Modem
1. Turn off the computer and peripheral devices.

2. Remove the computer's cover.  Refer to the computer manual, if 
   necessary, to see which rear panel screws to remove before sliding 
   the cover off.

   NOTE:  Our illustration shows expansion slots lined up vertically on 
   the floor of the computer.  Some computers are configured so that the 
   expansion slots are stacked horizontally, one on top of another.  
   The following instructions apply for both configurations.

3. Unscrew the solid bracket at the back of any available expansion slot.  
   (The modem board requires at least a standard half-card slot.)

   The bracket will pop out of the back, leaving an opening in the rear 
   panel for access to the modem's phone jacks and DIP switches.

4. Expansion slots have either a 3-inch-long groove, or a 3-inch and a 
   2-inch groove.  These grooves are lined on both sides with metal guides.  
   Insert the modem board into the slot you've chosen, as in Figure 3.3, 
   with the leads on the modem board's edge connector firmly in the 3-inch 
   groove.

5. Screw the vertical bracket at the back of the modem firmly to the 
   computer's rear panel, as shown in Figure 3.3.  This helps block radio 
   frequency emissions from the computer and keeps the modem board firmly 
   in place.

6. Replace the cover of the computer and replace the screws.

7. If you currently have a phone plugged into the wall jack, disconnect it.  
   Plug one end of the phone cable that came with the modem into the TELCO 
   jack at the rear of the modem.  This allows the modem to switch into the 
   telephone network, get a dial tone, and so on.  Plug the other end of 
   the cable into the wall jack.

   NOTE:  The phone cable is equipped with two standard, modular RJ11C 
   phone connectors.  If you have an older type of wall jack, you can 
   purchase an adapter and RJ11C connector from your phone company or 
   computer dealer.

8. If you wish, plug your phone's cord into the second jack on the modem, 
   labeled PHONE.  This enables you to use your phone for conventional 
   voice calls, and also allows you to switch between voice and data 
   transmission in the same call.  See Voice/Data Communications in 
   Appendix G for more information.

************************
Testing the Installation
Use the following procedures to verify that your modem is working properly.

1. Turn on your computer.  Then turn the Courier's power switch ON.  The 
   following front panel indicators, or LEDs, will light up on the modem. 
   
	CD      Carrier Detect, if you have set DIP switch 6 ON, enabling 
		the CD override
	TR      Data Terminal Ready, if you have set DIP switch 1 ON, 
		enabling the DTR override
	MR      Modem Ready/Power ON
	CS      Clear to Send

2. If you're using a personal computer, load your software to start the 
   program.  Set your terminal or software to 19.2K bps or 9600 bps.  
   In addition, set a word length of either 7 bits plus 1 parity bit, or 
   8 bits with no parity—it doesn't matter which at this time—and 1 Stop 
   bit.  Set the software to use the correct serial port (port through 
   which the modem connects to the computer).

3. Perform the function that lets you send AT commands to the modem, that 
   is, puts the computer in Terminal mode.  Some communications programs 
   do this automatically upon loading.  Others require you to display a 
   communications or terminal screen, type a Function key, or perform some 
   other operation.

   Review your communications software documentation for instructions. 

4. Send the following attention command.  Type either upper or lower case 
   letters, not a combination, and then press the Enter (Carriage Return) 
   key, shown in the example below between angle brackets.  (Don't type 
   the angle brackets.)
	
	AT <Enter>

   If everything is correct, the modem responds as follows:

	OK

   Go on to step 5.

   Troubleshooting
   If your entered command is not displayed, your local echo is OFF.  To turn 
   the local echo ON, send the modem the following command:  
    
      ATE1 <Enter>

   If double characters appear on the screen, both your modem and software are 
   set to local echo ON.  Either set your software to local echo OFF, or turn 
   the modem's echo OFF with the following command:
    
      ATE0 <Enter>

   If no OK appears on your screen after you completed Step 4, review the 
   following checkpoints:

   a. Make sure you type all upper or lower case letters and press <Enter>.
   b. Check to see that you set your communications software to the correct 
      serial port.  The correct serial port is the port to which the modem is 
      connected to the computer.
   c. Make sure your software has put the computer in Terminal mode, so that 
      you can send the modem commands.  Then review Step 4, on the previous 
      page.
   d. Be sure that DIP switches 1 and 6 are set ON or OFF according to your 
      terminal or software requirements.  The table in Appendix B explains 
      each function, and you may also need to review your terminal or 
      communications software documentation.
   e. If you set DIP switch 8 OFF, for Dumb mode, reset the modem to Smart 
      mode:  set DIP switch 8 to ON.
   f. The modem is shipped with DIP switch 3 ON, enabling the result codes.  
      If DIP switch 3 is OFF, set it to the ON position.  Then initiate the 
      new switch setting with the following reset command:
      
      ATZ <Enter>

5. As a final check, make sure the modem gets a dial tone.  Type the 
   following Dial command:
       
       ATD <Enter>

   On receipt of the command, the modem goes off hook and waits for a dial 
   tone.  The OH indicator lights up, and you'll hear the dial tone from 
   the modem's speaker.  To cancel the operation, press any key.

   Troubleshooting
   If you don't hear the dial tone, first increase the volume by using the 
   L command.  If that doesn't work, check to see that the phone cable from 
   the wall jack is connected to the correct jack on the modem.  If 
   necessary, reconnect the phone cable correctly.  Then try the Dial 
   command again, ATD <Enter>.

Chapter Four--Data Mode Operations

The information in this chapter applies to asynchronous calls only.  For 
synchronous operations, refer to Appendix F.

Detailed command descriptions are in this chapter.  Additional command 
summaries are in Appendix C, on the bottom panel of the modem, and in 
the Quick-Reference Card.

*****************
COMMAND SET USAGE

The Courier command set enables you to send the modem two kinds of 
instructions:

* operations, such as dialing or hanging up
* configurations, such as enabling error control or data compression

Follow these guidelines:

1. Your software must be loaded and, if you are using a computer, it must 
   be in Terminal mode.  
   
   Some communications programs put the computer in terminal mode 
   automatically when they are loaded.  Others require you to display a 
   communications terminal screen, press a Function key, or perform some 
   other operation.  Refer to your communications software documentation 
   for instructions.

   In Terminal mode the computer acts as if it were a standard terminal 
   such as a teletypewriter, rather than a data processor.  Keyboard 
   entries go directly to the modem, whether the entry is a modem command 
   or data to be transmitted over the phone lines.  Received data is 
   output directly to the screen. 

2. Type commands in either upper or lower case, not a combination (AT 
   or at--not At).

3. All commands except A/, A> and +++ are preceded by the AT (attention)
   prefix and are executed with the Enter/Carriage Return key (<Enter>).

4. Command length = 60 characters maximum.  The modem doesn't count the 
   AT prefix, Carriage Return character, or spaces.  It counts (but 
   doesn't act on) punctuation such as hyphens and parentheses.

5. A missing numeric parameter is assumed to be zero, as in the command 
   to hang up:  ATH <Enter> is the equivalent of ATH0 <Enter>.

   Example (spaces are not required, but are added here for readability):
  
	  AT &K3 X2 DT 071 312 1234 <Enter>

     AT      Attention; a command follows.
     &K3     Disable MNP5 data compression; use only V.42 bis compression.
     X2      Use the X2 result code subset.
     DT      Dial the following number using tone dialing.
     <Enter> Execute the commands.

This chapter groups related commands into the following categories.  
* Basic Commands
* Dialing/Answering
   Dialing
     Dial Options
     Cancel Dialing  
     Store Phone Numbers
     Redialing       
     Answer Mode
     Auto Answer
     Hanging Up
* Setting/Using Defaults
     Customizing NVRAM
     Resetting the Modem
* Configuration:
     Echo/Speaker
     Result Codes
     Modulation
     Error Control/Data Compression
     Data Rates 
     RS-232 Signal Operations
     Flow Control
* S-Registers
* Inquiry and Help 
* Testing
* International Calls
* Miscellaneous Commands

For an alphabetical listing of commands, check the first page of the index.

NOTE:  The defaults listed are based on the modem's shipping configuration:  
load from nonvolatile random access memory (NVRAM), DIP switch 10 OFF, 
which is the same as the &F1 configuration template).  For a complete 
listing of default configuration templates, see Appendix B.

**************
BASIC COMMANDS

AT      Attention command prefix.  Use AT alone to test for the OK result 
	code.  AT must prefix all commands except A/, A> and +++.

Any     Terminate the current dialing operation resulting from an
key     issued Dial command; terminate Repeat mode (> or A>).

*****************
DIALING/ANSWERING 

Dialing
Dn      Dial the specified phone number; also execute Dial options.
	The maximum number of characters allowed is 60, including the AT 
	prefix, punctuation and spaces.  The Carriage Return (Enter key) 
	isn't counted as a character.

	NOTE:  With the exception of the following Dial options, the 
	modem ignores any commands issued after D in the same command 
	string.  
	
Dial Options
D       Dial the number that follows and enter Originate mode.  Optional 
	parameters:

	P  Pulse dial.  Default.

	T  Tone dial.

	,  (Comma) Pause for 2 seconds before continuing to dial.

	;  Return to Command mode after dialing.  If your phone is 
	   plugged into the modem, you can use this option to have the modem 
	   Auto Dial a telephone rather than a modem.  The Courier dials, 
	   remains off hook and returns the OK message, indicating it is in 
	   Command mode.

	   For example, to have the modem place a voice call, enter the Dial 
	   command with a semicolon:  

		ATDT5551234; <Enter>

	   When the modem returns the OK result, pick up your phone receiver 
	   so you can talk to the other party, and send the command that 
	   hangs up the modem: 

		ATH <Enter>

	"  Dial the letters that follow (in an alphabetical phone number).  

	   NOTE:  If you are including another command after the dial string, 
	   use closing quotation marks before the additional command. 

       !   Transfer a call (flash the switch-hook).  This command applies to 
	   modems in installations where other modems share the phone line.  
	   The modem flashes the switch-hook (goes off hook 0.5 seconds, on 
	   hook for 0.5 seconds and off hook again) to dial the specified 
	   extension.

       W   This command is useful in situations where you must wait for a 
	   second dial tone before continuing dialing.  For example, if 
	   you need to dial for an outside line, the Courier continues 
	   dialing as soon as it detects the next dial tone.

		 AT DT 9 W 5551234 <Enter>

	   NOTE:  This command executes only if result code option X3 
	   or greater has been issued.  If the modem is set to X2 or lower, 
	   the modem interprets the W as a comma (two-second pause).

       @   Wait for an answer (with X3 or higher).  Some online services 
	   answer the phone and return a tape-recorded request for 
	   information before processing transactions.  In such instances, 
	   the @ command can be used in the Dial string to tell the modem 
	   to detect at least one ring, wait for five seconds of silence 
	   at the other end of the call, and then continue to execute the 
	   Dial string.
	   
	   To use the @ command, set the modem to X3, X4 or X7.  If the 
	   modem is set to X2 or lower, the modem returns an ERROR message 
	   when encountering the @ character in a command string.  If set 
	   to X5 or X6, the modem hangs up when it detects a voice answer 
	   and sends the VOICE result code.  

       /   A slash (/) causes a pause of only 125 milliseconds.

       R   Reverse frequencies.  This command allows calls to an 
	   originate-only modem.  It reverses the modem's originate/answer 
	   frequencies, forcing the Courier to dial out at the answer 
	   frequency.  The command follows the Dial command, before or 
	   after the phone number:

		 AT D1234567R <Enter> 

X2-X7   Adaptive dialing.  When any of the X2 through X7 options is in 
	effect and you do not issue a dialing type in the Dial string, 
	the Courier uses tone dialing, which is faster than the default 
	pulse type.  However, if the phone company's central office does 
	not have tone detection equipment, the modem cannot break dial 
	and continues to detect the dial tone.  If this occurs, the 
	modem automatically reverts to pulse dialing. 

DL      Dial the last-dialed number.  The modem stores each Dial command 
	until it receives the next Dial command.  Use DL instead of A/, 
	described on the next page, if you wish to send the modem non-Dial 
	commands before dialing again.

DSn     Dial the number stored in nonvolatile random access memory at 
	position n, where n = 0 through 9. 
   
Cancel Dialing
To cancel Dial-command execution, press any key. If you 
inadvertently hit a key on the keyboard while the modem is dialing, 
the call is canceled.  If this occurs, type the A/ command explained 
under Automated Redialing below. 

When the modem receives a command, it stores the instruction in 
its command buffer until it receives the next AT command.  Note 
that if you've sent the modem an additional command since the Dial 
command, A/ re-executes that command instead of redialing. 

Store Phone Numbers
&Zn=s   This command stores up to ten numbers, where n is the position 
	0 through 9 in nonvolatile memory, and s is the phone number string.  
	The number-string may be up to 40 characters long, including any 
	Dial command options.  

	      AT &Z2=555-6789 <Enter>

	Do not include modem settings in the &Zn string.  If the call 
	requires a special setting, insert it in the command string before 
	the DSn command.  In the following example, &M0 (no error control) 
	is inserted before the Dial command:

	      AT&M0 DS2 <Enter>

	NOTE:  The &Zn=s command functions differently when Dial Security 
	is enabled.  See Appendix D for more information.

&Zn?    Display the phone number stored in NVRAM at position n 
	(n = 0 through 9).

Redialing
A/      Re-execute the last issued command.  A/ doesn't take the AT prefix 
	or a Carriage Return, and can be used to redial.

		A/

   Automated Redialing (>, A>)
   While > and A> can be used to continuously repeat any command, 
   they are designed for automated redialing.

      Enter Repeat Mode
>       If you know the modem you are calling is frequently busy,
	include the Repeat command in the Dial string, as follows:
       
	       AT > DT 1234567 <Enter>  or
	       AT DT 1234567 > <Enter>

	The modem enters Repeat mode, dials the number, waits 60 seconds 
	for a carrier (default), and hangs up.  Then after a two-second 
	pause, it redials.  

	The cycle continues until the modems connect or the modem reaches a 
	maximum of 10 attempts.  The 10-try limit is mandated by Industry 
	Canada (IC) to prevent tying up local telephone company exchanges 
	with unconnected calls.

A>      This command combines the features of both the A/ and > commands.  
	The modem enters Repeat mode as described above, and redials the 
	Dial string in the command buffer.  Like the A/ command, A> does 
	not take the AT prefix or a Carriage Return.

     Exit Repeat Mode 
	Should you use > or A> with a command other than a Dial string, 
	abort the cycle by pressing any key.

	To abort automated redialing, be sure to press any key when the 
	result code appears, during the pause before the modem begins 
	dialing again.  If you press any key while the modem is dialing, 
	that dial attempt is canceled but the cycle continues.

Answer Mode
     Force Answer Mode
A       Force Answer mode when the modem hasn't received an incoming call.

     Auto Answer
	The Courier is shipped with DIP switch 5 ON, Auto Answer suppressed.  
	To set the modem to automatically answer incoming calls, do one of 
	the following: 

	1. Before powering on the modem, set DIP switch 5 OFF.  When you 
	   turn the computer on, the modem answers incoming calls on the 
	   first ring.

	2. When the modem is on, set your communications software to enable 
	   auto answer.  The following command instructs the modem to answer 
	   on the first ring.  (You can substitute a higher value.  See the 
	   S-Register summary in Appendix B.) 

		 AT S0 = 1 <Enter>

	When the modem senses a call coming in, it sends the result code 
	RING to your screen, goes off hook, and sends the remote modem a 
	high-pitched answer tone.  If there is no Carrier Detect within 
	60 seconds, the modem hangs up.  If the connection is made, the 
	modem sends a CONNECT result code.  When the call is disconnected 
	by you or the remote user, the modem hangs up and returns the NO 
	CARRIER code.

	NOTE:  If DIP switch 5 is OFF and S0=0, the Auto Answer will be 
	disabled.  Be sure that S0=1 through 256.

      Suppressing Auto Answer
	To disable Auto Answer, reverse Steps 1 or 2 above.  Set DIP switch 
	5 ON before powering on the modem, or set the modem to answer on 
	zero rings with the following command.

	      AT S0 = 0 <Enter>

   Points to Remember
	1. If the modem is attached to a computer, you can set the modem to 
	   receive calls when you're not at your computer.  Load your 
	   communications software as you normally do, and set the modem 
	   to Auto Answer.  Also set your software's host mode function 
	   to save incoming messages and/or files.

	2. If you've attached your phone so it can be used for conventional 
	   calls, disable Auto Answer when you are not expecting incoming 
	   data calls.  Otherwise, your modem may answer the phone before 
	   you do, greeting a voice caller with a high-pitched answer tone.

Hanging Up
Hn      On/off hook control.
	H0   Hang up (go on hook).
	H1   Go off hook.

+++     Escape code operations.  Once the modem is online to another system, 
	the only command it recognizes is an escape code of three typed 
	pluses, which forces the modem back to Command mode.  

	Do the following when issuing the command:  
	* Wait one second after sending the last item of data
	* Type: +++
	* Wait one second before typing any data

	Do not type the AT prefix or a Carriage Return.  The guard time of 
	one second before and after the code prevents the modem from 
	misinterpreting the occurrence of +++ in the transmitted data stream.  

	If necessary, the character used in the escape code or the duration 
	of the guard time can be changed by resetting Register S2 or S12.  
	See the S-Register Summary in Appendix B.

	In response to +++, the modem returns to Command mode.  However, 
	it keeps the line open or hangs up, depending on the setting of 
	DIP switch 9: 

	DIP Switch 9    Response to +++
	    OFF         Modem goes on hook (hangs up), sends NO CARRIER
			result code (factory setting)
	    ON          Modem maintains connection (Online-Command mode), 
			sends OK result code 

	The factory setting (OFF) forces an automatic disconnect when you 
	issue +++.   One advantage of this is that you are not likely to 
	inadvertently run up an all-night phone bill.  

	Set DIP switch 9 ON if you want the modem to respond to +++ by 
	entering Online-Command mode, enabling it to execute commands and 
	return online.  (See the O command, next.)  

	WARNING:  For unattended modem operations:  in rare instances, the 
	modem may fail to recognize the +++ escape code sequence.  If you 
	are running the modem under software control for unattended 
	operations, we suggest you use the sure fire method of dropping the 
	DTR signal from the computer or terminal for at least 50 
	milliseconds, to avoid costly phone charges.  Methods of turning 
	the DTR signal off--for example, closing the communications port--
	differ from one computer to another. 

   Returning Online 
On      If DIP switch 9 is ON (on detection of the escape code the modem 
	maintains the connection), you can issue commands and then toggle 
	the modem back online with the On command, as in this example:

		AT Q1 O <Enter>

	There are two ways to return online.
	ATO0    Return online (normal).  (Used in the example above.)
	ATO1    Return online and retrain.  Use to have the modem 
		re-synchronize if there were errors in a non-ARQ data 
		transfer.

   Hanging Up
	If DIP switch 9 is ON, the escape code forces the modem back to 
	Command mode but leaves the line open.  If you want the modem to 
	hang up, issue the following command once the modem sends the 
	OK result code:

		 ATH <Enter>

	If DIP switch 9 is OFF, the modem automatically hangs up on receipt 
	of the escape code.

**********************
SETTING/USING DEFAULTS

The modem's read-only memory (ROM) permanently stores the modem's four 
factory template settings.  Nonvolatile random access memory (NVRAM) 
allows you to save one of these four templates, or add your own 
modifications, and write all the settings to NVRAM as your power-on 
defaults.

&Fn     The modem is shipped with four configurations (templates), 
	&F0 through &F3, stored in permanent nonprogrammable memory (ROM).  
	Appendix B includes configuration listings for each template.  
	Any one of the templates may be loaded into current memory (AT &Fn) 
	or written to nonvolatile memory to serve as the reset default 
	(AT &Fn &W).  Note, however, that &F0 is always loaded into memory 
	if DIP switch 10 is ON. 

	When you power on the Courier, it loads the settings stored in 
	NVRAM if DIP switch 10 is OFF.  Until you write your own settings 
	to NVRAM, the defaults stored there are the same as the permanent 
	ROM factory settings stored in position 1, &F1.


	To view the &F1 settings, select option 5 of the I (inquiry) command:
   
		   AT I5 <Enter>

Customizing NVRAM
&W      To substitute a template other than &F1, write the desired template 
	to NVRAM, using the &W command.
  
		  AT &F2 &W <Enter>

	To modify the &Fn configuration in NVRAM, type your changes and 
	then save them to NVRAM, as in the following example.  The original 
	factory template remains intact.

		  AT M2 S10=40 &A2 &W <Enter>\

	NOTE:  When writing a different default configuration to NVRAM, 
	insert any additions after the &Fn command but before &W.  Otherwise 
	they will be overwritten by &Fn.

	After sending a configuration to NVRAM, you can change any setting 
	just for the current session, as in the following example.  The 
	NVRAM configuration remains intact. 

		  ATX6 <Enter>  

	But if you want the new setting to be a default, write it to 
	NVRAM at the same time, as in the following example.  X7 is 
	substituted for the Xn value stored earlier.  Any other setting 
	that was changed and can be saved to NVRAM will also be saved. 
	
		  AT X7 &W <Enter>

Resetting the Modem
Z       Software reset to NVRAM settings when DIP switch 10 is OFF (factory 
	setting).  If DIP switch 10 is OFF, the modem resets to the &F0 
	configuration template, with no flow control.

	NOTE:  Use the ATZ command also if you've changed the position of 
	DIP switches 1 through 7 or 9 while the modem is on, so that the 
	modem can read the new setting.  The only other way to initiate 
	a new setting for switches 1 through 7 and 9 is to turn the modem 
	off and on again. 


*************
CONFIGURATION

Echo/Speaker
En      Command mode local echo.  Enables/disables the display of your 
	typed commands.  If double characters appear on the screen, both 
	the modem's local echo and your software's local echo are on.  

	The Courier is shipped with DIP switch 4 OFF, enabling local echo.  
	The En command controls the local echo for a current session, 
	independently of the switch setting.  At power-on and reset, the 
	modem operates according to the DIP switch setting.  The En command 
	is not stored in nonvolatile memory as a power-on/reset default.

	E0      Command mode echo OFF.  The modem does not display keyboard 
		commands.
	E1      Command mode echo ON.

Fn      Online local echo.  This command causes the modem to display a copy 
	of the data it is transmitting to another system.  Many systems, 
	however, return a copy of received data, which is called a remote 
	echo.  If the modem's online echo is ON and there is also remote 
	echoing, double characters appear on the screen.  

	In some microcomputer documentation, the term duplex is applied to 
	local online echoing, although the term is not technically accurate.

	F0      Online echo ON.  Sometimes called half duplex.  As the 
		modem transmits data to a remote system, it also sends a 
		copy of the data to the screen.
	F1      Online echo OFF.  Sometimes called full duplex.  Default.

Mn      Speaker (audio monitor).
	M0      The speaker is always OFF.
	M1      The speaker is ON until carrier is established.  Default.
	M2      The speaker is always ON, including during data transfer.
	M3      The speaker is ON after the last digit is dialed and remains 
	ON until carrier is established.

Result Codes
Qn      Enable/suppress the display of result codes.  The Courier is 
	shipped with DIP switch 3 ON, to display result codes.  Use the 
	Qn command to control the display for a current session, 
	independently of the switch setting. 

	At power-on and reset, the modem operates according to the DIP 
	switch setting.  The Qn command is not stored in nonvolatile 
	random access memory.

	Q0      Result codes displayed.
	Q1      Result codes suppressed (quiet).
	Q2      Result codes suppressed in Answer mode.

Vn      Return result codes in words or numbers (Verbal/Numeric mode). 
	At power-on and reset, the modem operates according to the DIP 
	switch setting.  The Vn command is not stored in nonvolatile 
	memory as a power-on/reset default.
	V0      Numeric mode.
	V1      Verbal mode.

Xn     Result code set options.  Use the following table (Default = X7, 
       all codes except 12/VOICE).  For result codes for synchronous 
       operations, see Appendix F.

					 Setting        
Result Codes    X0      X1      X2      X3      X4      X5      X6      X7
0/OK            ·       ·       ·       ·       ·       ·       ·       ·
1/CONNECT       ·       ·       ·       ·       ·       ·       ·       ·
2/RING          ·       ·       ·       ·       ·       ·       ·       ·
3/NO CARRIER    ·       ·       ·       ·       ·       ·       ·       ·
4/ERROR         ·       ·       ·       ·       ·       ·       ·       ·
5/CONNECT 1200          ·       ·       ·       ·       ·       ·       ·
6/NO DIAL TONE                  ·               ·               ·       ·
7/BUSY                                  ·       ·       ·       ·       ·
8/NO ANSWER                             ·       ·       ·       ·       ·
9/RESERVED
10/CONNECT 2400         ·       ·       ·       ·       ·       ·       ·
11/RINGING                                              ·       ·       ·
12/VOICE                                                ·       ·       
13/CONNECT 9600         ·       ·       ·       ·       ·       ·       ·
18/CONNECT 4800         ·       ·       ·       ·       ·       ·       ·
20/CONNECT 7200         ·       ·       ·       ·       ·       ·       ·
21/CONNECT 12000        ·       ·       ·       ·       ·       ·       ·
25/CONNECT 14400        ·       ·       ·       ·       ·       ·       ·
43/CONNECT 16800        ·       ·       ·       ·       ·       ·       ·
85/CONNECT 19200        ·       ·       ·       ·       ·       ·       ·
91/CONNECT 21600        ·       ·       ·       ·       ·       ·       ·
99/CONNECT 24000        ·       ·       ·       ·       ·       ·       ·
103/CONNECT 26400       ·       ·       ·       ·       ·       ·       ·
107/CONNECT 28800       ·       ·       ·       ·       ·       ·       ·

Functions
Adaptive Dialing                ·       ·       ·       ·       ·       ·
Wait for 2nd Dial Tone (W)              ·       ·       ·       ·       ·
Wait for Answer (@)                     ·       ·       ·       ·       ·
Fast Dial               ·               ·               ·       ·

NOTE:  Additional messages indicate an error control connection and the 
modulation for a call.  See the next section, Additional Result Code 
Subsets.

Result Code     Meaning
0/OK            Command has been executed.
1/CONNECT       Connection with another modem; if set to X0, connection may 
		be between 300 and 28.8 bps; if X1 or higher, connection is 
		at 300 bps.
2/RING          Incoming ring detected.
3/NO CARRIER    Carrier detect has failed or carrier has been dropped due to 
		disconnect.
4/ERROR         Command is invalid.
5/CONNECT 1200  Connection with another modem at 1200 bps.
6/NO DIAL TONE  Dial tone not detected during the normal 2 seconds, set in 
		Register S6.
7/BUSY          Busy signal detect; modem hangs up.
8/NO ANSWER     After waiting 5 seconds for an answer, modem hangs up; 
		returned instead of NO CARRIER when the @ option is used.
10/CONNECT 2400 Connection with another modem at 2400 bps.
11/RINGING      The modem has dialed; remote phone line is ringing.
12/VOICE        Voice answer at remote site; modem hangs up.
13/CONNECT 9600 Connection at reported rate.  Same meaning for results of 
		4800 (18), 7200 (20), 12K (21), 14.4K (25), 16.8K (43), 
		19.2K (85), 21.6K (91), 24K (99), 26.4K (103), or 28.8K (107)

Adaptive        The modem attempts to use tone dialing and, if that 
Dialing         doesn't work, reverts to rotary dialing.

Wait for        The modem continues dialing as soon as it detects 
Another Dial    another dial tone.  See the dial options earlier in this 
Tone (W)        chapter.

Wait for an     The modem continues dialing when it detects 5 seconds of 
Answer (@)      silence on the line.  See the dial options earlier in this 
		chapter.

Fast Dial       The modem dials immediately on dial-tone detect, instead of 
		waiting the normal 2 seconds set in Register S6.


Additional Result Code Subsets 
NOTE:  ARQ (Automatic Repeat Request) is used in this manual to denote 
calls under error control.

&An     Enable/disable additional result code subsets.  See the Xn 
	command earlier in this chapter.
	&A0     ARQ result codes are disabled.  This setting does not affect 
		an error control connection; the modem returns the standard 
		CONNECT messages if result codes are enabled.

	&A1     ARQ result codes are enabled, indicating that a connection 
		is under error control.  Message 14 is displayed if the 
		modem is set to X0 and the connection is at any rate from 
		1200 to 28.8K bps.  The remaining results indicate the 
		connection rate and require a setting of X1 or higher.

		    14/CONNECT/ARQ          47/CONNECT 16800/ARQ
		    15/CONNECT 1200/ARQ     88/CONNECT 19200/ARQ
		    16/CONNECT 2400/ARQ     94/CONNECT 21600/ARQ
		    17/CONNECT 9600/ARQ     100/CONNECT 24000/ARQ
		    19/CONNECT 4800/ARQ     104/CONNECT 26400/ARQ
		    22/CONNECT 12000/ARQ    108/CONNECT 28800/ARQ
		    24/CONNECT 7200/ARQ
		    26/CONNECT 14400/ARQ

	&A2     Additional VFC, V34, HST, or V32 modulation indicator.  
		Included for users of HST Dual Standard modems.  If your 
		software cannot handle the added modulation information, 
		select &A1 or &A0.

		23/CONNECT 9600/HST      27/CONNECT 9600/ARQ/HST
		28/CONNECT 4800/HST      29/CONNECT 4800/ARQ/HST
		30/CONNECT 7200/HST      34/CONNECT 7200/ARQ/HST 
		31/CONNECT 12000/HST     32/CONNECT 12000/ARQ/HST        
		35/CONNECT 14400/HST     36/CONNECT 14400/ARQ/HST        
		53/CONNECT 16800/HST     57/CONNECT 16800/ARQ/HST        
		33/CONNECT 9600/V32      37/CONNECT 9600/ARQ/V32
		38/CONNECT 4800/V32      39/CONNECT 4800/ARQ/V32
		40/CONNECT 7200/V32      44/CONNECT 7200/ARQ/V32
		41/CONNECT 12000/V32     42/CONNECT 12000/ARQ/V32
		45/CONNECT 14400/V32     46/CONNECT 14400/ARQ/V32
		83/CONNECT 16800/V32     84/CONNECT 16800/ARQ/V32
		87/CONNECT 19200/V32     90/CONNECT 19200/ARQ/V32
		93/CONNECT 21600/V32     96/CONNECT 21600/ARQ/V32
		97/CONNECT 21600/VFC     98/CONNECT 21600/ARQ/VFC
		101/CONNECT 24000/VFC    102/CONNECT 24000/ARQ/VFC
		105/CONNECT 26400/VFC    106/CONNECT 26400/ARQ/VFC
		109/CONNECT 28800/VFC    110/CONNECT 28800/ARQ/VFC
		139/CONNECT 14400/VFC    141/CONNECT 14400/ARQ/VFC
		143/CONNECT 16800/VFC    145/CONNECT 16800/ARQ/VFC
		147/CONNECT 19200/VFC    149/CONNECT 19200/ARQ/VFC
		111/CONNECT 21600/V34    112/CONNECT 21600/ARQ/V34
		113/CONNECT 24000/V34    114/CONNECT 24000/ARQ/V34
		115/CONNECT 26400/V34    116/CONNECT 26400/ARQ/V34
		117/CONNECT 28800/V34    118/CONNECT 28800/ARQ/V34
		120/CONNECT 2400/V34     122/CONNECT 2400/ARQ/V34
		124/CONNECT 4800/V34     126/CONNECT 4800/ARQ/V34
		128/CONNECT 7200/V34     130/CONNECT 7200/ARQ/V34
		132/CONNECT 9600/V34     134/CONNECT 9600/ARQ/V34
		136/CONNECT 12000/V34    138/CONNECT 12000/ARQ/V34
		140/CONNECT 14400/V34    142/CONNECT 14400/ARQ/V34
		144/CONNECT 16800/V34    146/CONNECT 16800/ARQ/V34
		148/CONNECT 19200/V34    150/CONNECT 19200/ARQ/V34


	&A3     Additional error control indicator (LAPM, HST, MNP, SYNC, or 
		ONE) and data compression type (V42BIS or MNP5).  Default.  
		When the call is not under one of those protocols (and ARQ 
		is not included in the result code), the modem reports 
		either SYNC, indicating a synchronous connection, or 
		NONE, for no protocol.  

		If the modems are using data compression, the type of 
		compression, V42BIS or MNP5, is added to the result code.  
		In the first of the following examples, the modems 
		negotiated error control for the call (ARQ), used VFC 
		modulation, are using the LAPM error control protocol, and 
		are using V.42 bis compression.

		CONNECT 28800/ARQ/VFC/LAPM/V42BIS         [or MNP/MNP5]
		CONNECT 19200/ARQ/V32/LAPM/V42BIS         [or MNP/MNP5]
		CONNECT 16800/ARQ/HST/HST/V42BIS          [or MNP/MNP5]
		CONNECT 14400/ARQ/V32/LAPM/V42BIS         [or MNP/MNP5]
		CONNECT 9600/ARQ/HST/CELLULAR/HST/V42BIS  [or MNP5]
		CONNECT 9600/SYNC
		CONNECT 2400/NONE

		NOTE:  Although these codes will return numeric identifiers, 
		they are the same numeric identifiers used for &A2 result 
		codes.  If the modem is in Numeric mode (V0) and set to 
		&A3, you will not be able to differentiate between &A2 and 
		&A3 result codes.  &A3 result codes may not be compatible 
		with some software.

Modulation
Bn      Handshake options.  There are three commands that apply to 
	international calls above 1200 bps--Bn, &Gn, &Pn.  See International 
	Calls later in this chapter for information on the other two 
	settings.
	B0      ITU-T (formerly CCITT) answer sequence.  Default.  This 
		is required to answer all V.32-type calls, as well as 
		calls from overseas.
	B1      Bell answer tone.  This setting selects HST modulation 
		in Dual Standard modems, but should only be used if the 
		modem is not required to answer V.32-type calls.  

		NOTE:  This setting is required for HST cellular calls.

Error Control/Data Compression
&Mn     Enable ARQ (error control) or synchronous protocols.  Both your 
	modem and the remote modem must use the same protocol.
	&M0     Normal mode, no error control.  Due to the nature of phone 
		line channels, this is never recommended for calls above 
		2400 bps.  
	&M1     This setting is exclusive of the modems' error control and 
		is used only for online synchronous mode without V.25 bis.  
		See Appendix F for more information.
	&M2     Reserved.
	&M3     Reserved.
	&M4     Normal/ARQ mode.  Default.  If an ARQ connection isn't made, 
		the modem operates in Normal mode, as though it were set to 
		&M0.

		NOTE:  When V.32-type modems revert to Normal mode, they 
		transfer data at high speeds without the reliability 
		of error control.  To avoid this, both local and remote 
		modems should always be set for error control.  Modems in 
		HST mode, if unable to establish an error control connection, 
		drop to 2400 bps.

	&M5     The modem enters ARQ asynchronous mode.  The modem hangs up 
		if an ARQ connection cannot be made.  
	&M6     The modem enters V.25 bis synchronous mode, using a 
		character-oriented link protocol similar to BISYNC.  See 
		Appendix F for more information.
	&M7     The modem enters V.25 bis synchronous mode, using the HDLC 
		link protocol.

&Kn     Enable/disable data compression.
	&K0     Data compression disabled.
	&K1     Auto enable/disable.  Default.  The modem enables 
		compression if the serial port rate is fixed, &B1.  It 
		disables compression if the serial port rate follows the 
		connection rate, &B0, because compression offers no 
		throughput advantage when the serial port and connection 
		rates are equal.  Compression may even degrade throughput. 
	&K2     Data compression enabled.  Use this setting to keep the 
		modem from disabling compression. 
	&K3     Selective data compression.  The modem negotiates only for 
		V.42 bis compression, and disables MNP Level 5 (MNP5) 
		compression.  Use this setting to transfer 8-bit binary 
		files, .ZIP files, and other files that are already 
		compressed.  See the note below.  

	NOTE:  MNP5 compression is not useful when transferring 
	files that are already compressed, such as the .ZIP files 
	downloaded from many Bulletin Boards and 8-bit binary files, 
	which appear to the modem to be compressed.  MNP5 tends to 
	add data to the transmission so that throughput over the 
	link degrades.  V.42 bis compression dynamically detects 
	when data is already compressed and turns off until it 
	detects that compression will work to advantage.  The 
	special &K3 setting enables the best throughput for already-
	compressed files.  

	See Throughput Guidelines and Data Compression in Appendix A for 
	more information, including throughput to expect for different 
	kinds of files.

Data Rates
The modem can be set to a fixed or variable serial port rate.  A fixed rate 
sets the modem for the highest possible throughput and provides the best 
performance.  A variable rate allows the modem to switch to match the more 
limited rate on the phone connection.

Your software must support fixed or variable serial port rates, and must be 
set to either of the two settings.  NOTE:  Your software may refer to these 
options with terms like locked serial port (fixed rate) or autobaud (variable 
rate).

&Bn     Serial port rate variable or fixed.
	&B0     Variable rates.  When the modem switches its connection rate 
		to connect with a modem operating at a different rate, it 
		also switches its serial port rate.  The software or 
		terminal also switches serial port rates to match the 
		connection rate.  

	&B1     Fixed rate.  Default.  The modem always communicates with 
		the terminal or computer at the rate at which you have set 
		the terminal or software, regardless of the connection rate.  
		For the greatest throughput, set the serial port to 115.2K, 
		57.6K, 38.4K bps for high speed calls and to at least 9600 
		bps for 2400-bps calls.

		This setting is not affected by the &N setting.  However, 
		the serial port rate must be equal to or higher than the &Nn 
		rate.

	&B2     Fixed for ARQ calls/Variable for non-ARQ calls.  Answer mode 
		only.  When the modem goes off hook and connects in ARQ 
		mode, it shifts its serial port rate up to a user-specified 
		rate, for example, 38.4K bps.  If the connection is not 
		under error control, the modem behaves as if it were set 
		to &B0 and switches its serial port rate to match the 
		connection rate of each call.

		To implement this feature, first set your software to the 
		desired rate.  Then send the modem the AT &B2 [other 
		settings] &W command.  

		The modem stores the rate of the command in NVRAM along 
		with the settings.  Each time it makes an ARQ connection, 
		the modem checks NVRAM for the specified serial port rate. 

		When sending subsequent configurations to NVRAM, be sure 
		your software is set to your selected serial port rate, 
		so that the correct rate is maintained.

&Nn     Connection rate variable or fixed.
	&N0     Variable rates.  Default.  The Courier negotiates with 
		the remote modem for the highest possible connection rate, 
		depending on the capabilities of the remote modem. 

	&N1-    Fixed rate.  The modem only connects if the remote
	&N14    modem is operating at the same rate.  If not, the modem 
		hangs up.  If you wish, you can filter out calls at other 
		than a specific rate, for security or other reasons, by 
		fixing the connection rate.

		The connection rate must always be lower than, or equal to, 
		the serial port rate, never higher.  
       
		The options are as follows.
		&N1       300 bps       &N8     14.4K bps
		&N2      1200 bps       &N9     16.8K bps 
		&N3      2400 bps       &N10    19.2K bps
		&N4      4800 bps       &N11    21.6K bps
		&N5      7200 bps       &N12      24K bps 
		&N6      9600 bps       &N13    26.4K bps
		&N7       12K bps       &N14    28.8K bps

************************
RS-232 Signal Operations
&Cn     Carrier Detect operations.  At power-on and reset, the modem 
operates according to the setting of DIP switch 6.  This command 
is not stored in nonvolatile memory as a power-on/reset default.
&C0     CD override, CD always ON.
&C1     Normal CD operations.  The Courier sends a CD signal when 
it connects with another modem and drops the CD when it 
disconnects.

&Dn     Data Terminal Ready (DTR) operations.  At power-on and reset, 
	the modem operates according to the setting of DIP switch 1.  
	This command is not stored in nonvolatile memory as a 
	power-on/reset default.
	&D0     DTR override.  The modem operates as though the DTR is 
		always ON.

	&D1     Advance usage:  If issued before connecting with another 
		modem, the modem can enter online command mode during a 
		call by toggling DTR.  (Most communications software 
		packages have a method for toggling DTR.)  &D1 functions 
		similarly to the escape code (+++), except that this setting 
		is independent of DIP switch 9.

		If DIP Switch 1 is ON (DTR override) when you issue the 
		&D1 command, the DTR override is automatically turned off.  
		However, if you change the setting of DIP switch 1 after 
		issuing &D1, the DIP switch setting takes precedence.

		Return online with the On command, or hang up with the Hn 
		command.

	&D2     Normal DTR operations.  The terminal or computer must send 
		a DTR signal for the modem to accept commands.  Dropping 
		DTR terminates a call.

&Sn     The modem sends the computer or terminal a Data Set Ready (DSR) 
	signal via the RS-232 interface.  (Data Set is industry jargon for 
	modem.)  Few, if any, commercial communications programs require 
	the modem to control DSR, &S1.  Leave the modem set for DSR 
	overridden, &S0, unless you know that your installation requires 
	a different setting.
	&S0     DSR is always ON (override).  Default.
	&S1     In Originate mode, the modem sends the DSR after it 
		dials, when it detects the remote modem's answer tone.  
		In Answer mode, the modem sends the DSR after it sends an 
		answer tone.
	&S2     This option is for specialized equipment such as automatic 
		callback units.  On loss of carrier, the modem sends a 
		pulsed DSR signal with Clear to Send (CTS) following 

Carrier Detect (CD).
	&S3     This is the same as &S2, but without the CTS following CD.
	&S4     The modem sends the computer a DSR signal at the same time 
		that it sends the Carrier Detect (CD) signal.
	&S5     CTS follows Carrier Detect with SSR normal

************
Flow Control
Flow control allows the modem to monitor the amount of data coming from the 
computer or the remote modem, and notify either end if its buffers are too 
full, so that they stop sending data for a moment.

The modem uses either hardware or software flow control.  Your software and 
machine must support whichever type you select.  

Hardware Control
The modem drops the Clear to Send (CTS) signal it's been sending to the 
computer or terminal when the modem's buffer nears 90% capacity.  It starts 
sending CTS again when the buffer is about half full.

Software Control
The modem sends the computer or terminal the standard ASCII Transmit OFF 
(XOFF) character, <Ctrl>-S, when its buffer nears 90% capacity.  The modem 
sends the ASCII Transmit ON character, <Ctrl>-Q, when the buffer is about 
half full.  ASCII definitions are as follows:

XON      <Ctrl>-Q       (ASCII 17 Decimal, 11 Hex)
XOFF     <Ctrl>-S       (ASCII 19 Decimal, 13 Hex)

NOTE:  You should set your software as well to either hardware or software 
flow control.  Some programs also require that you turn off the type you are 
not using.

The ASCII characters may be user-defined.  See Registers S22 and S23 in 
Appendix B.  That appendix also includes an ASCII chart. 

WARNING:  If possible, always use hardware flow control, the factory 
default.  You may lose data if XON/XOFF (<Ctrl>-S, <Ctrl>-Q) characters 
occur in the data stream from other sources.  They may, for example, come 
from the remote system:  an XON from the remote system, after your modem 
has sent an XOFF, can result in buffer overflow.  

<Ctrl>-S (XOFF) and <Ctrl>-Q (XON) characters also occur in binary files, 
and are used by Xmodem-type protocols.  You risk having these characters 
misinterpreted as modem flow control characters and dropped from the data 
stream.

If you cannot use hardware flow control and if you're transferring non-text 
(binary) files, or using an Xmodem-type protocol, disable flow control 
entirely (&H0).  In addition, be sure the modem is set to &B0 and &N0, so 
that the serial port and connection rates are equal.

   Transmit Data Buffer Sizes
      The Transmit Data refers to the data from the computer, which the 
      modem is to transmit over the phone line.

      The size of the Transmit data buffer depends on whether the connection 
      is under error control or not, as follows.

      * ARQ connections:  3.25K bytes.
      * Non-ARQ connections:  1.5K bytes, allowing use of error control file 
	transfer protocols such as Xmodem and Ymodem without flow control.

      If bit 3 of Register S15 is turned on, the non-ARQ buffer size is 
      reduced to 128 bytes, for the convenience of BBS operators taking 
      calls from remote users of slower modems.  See S-Register Summary, 
      S15, in Appendix B.

   Received Data Buffer Size
     Received Data refers to the data the modem receives over the phone 
     link, which the modem passes on to the attached computer.

     The size of this buffer remains constant at 2K bytes.

Transmit Data Flow Control 
&Hn     This type of flow control is for data transmitted to the modem by 
its attached computer or terminal.  The modem monitors its buffer 
as data comes from the computer or modem.  If the buffer approaches 
90% capacity, the modem signals the computer or terminal to stop 
transmitting.  When the modem has sent enough data over the link 
to half empty the buffer, it signals the computer or terminal to 
resume transmitting.

	&H0     Transmit Data flow control disabled.
	&H1     Hardware flow control.  Default.  Requires that your 
		computer or terminal and software support Clear to Send 
		(CTS) at the RS-232 interface.
	&H2     Software flow control.  Requires that your software 
		support XON/XOFF signaling.
	&H3     Use both hardware and software flow control.  If you are 
		unsure about what your equipment supports, select this 
		option.  But keep the warning, above, in mind about software 
		flow control.

Received Data Flow Control
Separate commands, &Rn (hardware) and &In (software), control the flow of 
Received Data passed by the Courier to your computer or terminal.

Your software and machine must support whichever type you select, although 
we recommend hardware flow control, if possible.

   Hardware Control(&Rn)
     &R0     Delay Clear to Send Response after Request to Send signal 
	     (RTS/CTS delay).  The delay is required by some synchronous 
	     mainframes and does not apply to asynchronous calls.
     &R1     The modem ignores RTS.  This setting is required if your 
	     computer or terminal or software does not support RTS.
     &R2     Hardware flow control of received data enabled.  Default.  
	     The modem sends data to the computer or terminal only on 
	     receipt of the RTS signal.

   Software Control (&In)
     WARNING:  In ordinary operation, the only characters the modem 
     recognizes during a call are the three pluses (+++) of the escape 
     code.  But when software flow control is enabled, the modem also looks 
     for <Ctrl>-S or <Ctrl>-Q characters.  If these characters occur in a 
     file or as part of a protocol, the modem reads them as XON/XOFF 
     characters and acts on them.  In some cases, the modem drops them 
     from the data stream.

     &I0     Disables XON/XOFF flow control of received data.  Default.  
	     Recommended for non-ARQ (Normal mode) calls, but see &I5.  
	     The I0 option provides transparency for all characters except 
	     the escape code sequence (+++), because at this setting the 
	     modem does not look for control characters.
       
	     NOTE:  Because of the risk described in the above warning, the 
	     settings that follow are only recommended for users whose data 
	     does not include XON/XOFF control characters.

     &I1     The Courier acts on your typed XON/XOFF commands, <Ctrl>-S or 
	     <Ctrl>-Q, and passes them to the remote computer.  Use in ARQ 
	     mode only, but keep in mind that the XON/XOFF characters sent 
	     to the remote computer may interfere with XON/XOFF signaling 
	     between the remote computer and remote modem.  See &I2.

     &I2     The Courier acts on your XON/XOFF commands, but removes them 
	     from the data stream instead of passing them to the remote 
	     computer.  This ensures that the remote computer does not 
	     confuse your XON/XOFF characters with those from its attached 
	     modem.  This is the recommended setting for ARQ mode.

	     However, if the call is not in ARQ mode, there is no flow 
	     control on the phone link.  If you send an XOFF to your modem 
	    and it stops passing data, it has no way to tell the remote 
	     computer and modem to stop sending for a while, and your 
	     modem's buffer may overflow.  For more reliable control in 
	     non-ARQ mode, see &I5.

     &I3     Hewlett PackardSYMBOL 190 \f "Symbol"Host mode.  Applies only 
	     to modems attached to an HP mainframe that uses the ENQ/ACK 
	     protocol.  Use in ARQ mode only.  See Appendix G.

     &I4     Hewlett PackardSYMBOL 190 \f "Symbol"Terminal mode.  Applies 
	     only to modems attached to terminals in an HP system that uses 
	     the ENQ/ACK protocol.  Use in ARQ mode only.  See Appendix G.

     &I5     This setting is designed to enable flow control on the phone 
	     link when the connection is not under error control.  For this 
	     to work for you, the remote modem must also have &I5 capability.

	     In ARQ mode, a Courier set to &I5 operates the same as it does 
	     when set to &I2.  It acts on your XON/XOFF commands, but does 
	     not pass them to the remote system.  The error control protocol 
	     enables the modems to control the flow of data on the phone 
	     link.
       
	     In non-ARQ mode, a Courier set to &I5 operates as though flow 
	     control were disabled (&I0);  it does not look for your typed 
	     XON/XOFF commands.  However, it looks for XON/XOFF characters 
	     coming in over the phone link.  When the remote operator sends 
	     XON/XOFF commands, the Courier either resumes or stops 
	     transmitting data over the link and drops the characters from 
	     the data stream.

	     If both modems are set to &I5, operators at each end can signal 
	     the remote modem to stop sending, thereby controlling the data 
	     flow on the phone link and preventing their own modem's buffer 
	     from overflowing.  At the computer or terminal/modem 
	     interfaces, the modems independently control the flow of 
	     data through their Transmit Data (&H) settings.

   Guidelines
     Use of software flow control may prove satisfactory if you're only 
     transferring text files.  However, if you're transferring non-text 
     (binary) files, or using an Xmodem-type protocol, disable flow control 
     entirely (&R1, &I0).  In addition, set the modem to &B0 and &N0, so 
     that the serial port and connection rates are equal.

***********
S-REGISTERS

The S-Registers are used to set various timing parameters, redefine selected 
ASCII characters, and other configuration options.  A detailed summary of 
the S-register functions is in Appendix B.  A less detailed summary is in 
the Quick-Reference card. 

Sr=n    Set S-Register value:  r is any S-Register; n must be a decimal 
	number between 0 and 255.

Sr.b=n  Alternative command for setting bit-mapped registers:  r is the 
	bit-mapped register; .b is the bit; n is 0 (off) or 1 (on).

Sr?     Query contents of register r.

****************
INQUIRY AND HELP

The modem displays information such as the current modem settings, product 
code, and call duration.  It also displays summary information for every 
command that the modem supports.

For more information on Inquiry and Help commands, including sample 
displays, see Chapter 6.

*******
TESTING

The modem can perform a number of tests including Analog Loopback, Digital 
Loopback, and Remote Digital Loopback.  These tests can be used to check 
the operations of the modem's transmitter and receiver, or to locate a 
problem with a remote modem or telephone channel.  Error control must be 
disabled for these tests.

See Appendix H for more information. 

*******************
INTERNATIONAL CALLS

There are three commands that apply to international calls above 1200 
bps--Bn, &Gn, &Pn.  Bn is described earlier in this chapter.

&Gn     This setting applies only to overseas calls at 2400 or 1200 bps.  
	British phone switching systems require the modem to send an 1800 
	Hz guard tone after it sends an answer tone.  Some other European 
	phone networks require a 550 Hz guard tone.  Guard tones are not 
	used in the United States or Canada.

	&G0     No guard tone.  This is used in the U.S. and in Canada.  
		Default.
	&G1     This sets a 550 Hz guard tone, and is used in some European 
		countries.
	&G2     This sets an 1800 Hz guard tone, and is used in the U.K. 
		and some Commonwealth countries.  &G2 requires the B0 
		setting.

&Pn     This command sets the ratio of the off-hook/on-hook (make/break) 
	interval for pulse dialing.  The default sets the modem for use in 
	North America.  The ratio must be changed if the modem is used 
	in the United Kingdom and some Commonwealth countries.

	&P0     Make/break ratio, U.S./Canada:  39%/61%.  Default.  
	&P1     Make/break ratio, United Kingdom, some Commonwealth 
		countries:  33%/67%.

**********************
MISCELLANEOUS COMMANDS

Cn      Transmitter enabled/disabled.
C0      Transmitter disabled; receive-only condition.
C1      Transmitter enabled.  Default.

Kn      Modem clock operation:  Call-duration or Real-time mode.  Displayed 
	with ATI3 and ATI6 commands.
	K0      Display current call-duration if online.  Display last 
		call-duration if offline.  Default.
	K1      Return actual time at ATI3.  Clock is set using 
		ATI3=HH:MM:SS K1.

&Yn     Break handling.  This command allows you to send a break to abort 
	data transfer without disconnecting from the phone link.
	&Y0     Destructive, don't send Break.
	&Y1     Destructive, expedited (Default).
	&Y2     Nondestructive, expedited.
	&Y3     Nondestructive, unexpedited; modem sends Break in sequence 
		with data received from computer or terminal.

	NOTE:  If the call is under MNP5 data compression, destructive 
	Breaks cause both modems to reset their data compression tables.  
	When transmission resumes, the modems build new tables, and the 
	result is lower than normal throughput. 

&ZC=s  Write the following command string s to NVRAM.  The command string 
       may be up to 30 characters long; spaces are not counted.  This 
       command can be used so that you can call another modem without 
       loading your communications software.

       After storing a command, you can program the voice/data switch to 
       execute the stored command string when pressed.  The following 
       example assigns a command string that displays the link diagnostics 
       screen when you press the voice/data switch.  
       
	      AT&ZC=I6 <Enter>

       The function of the voice/data switch is determined by the setting 
       of Register S32, as described in Appendix G.  Set the voice/data 
       switch function to execute stored command string by setting Register 
       S32 to 9 with the following command:

	      ATS32=9 <Enter>

       Note that you can reset the voice/data switch at any time to one of 
       the other available functions.  Additionally, you can overwrite the 
       stored command string with a new one at any time.

       Once you've stored your command string and set Register S32, all 
       you need to do is press the voice/data switch whenever you want 
       the command string executed.

&ZC?    Display the stored command string.

%T      Enables the modem, when off hook, to detect the tone frequencies of 
	dialing modems.  %T is meant primarily for use with network 
	applications, but may also be integrated into certain software 
	programs.  For example, %T could be used in a security program to 
	identify incoming tone security codes.

	To enable %T, type ATH1 <Enter> to force the modem off hook.  Then 
	type AT%T <Enter>.  

	To return the modem to Command mode, press any key or drop the 
	computer's or terminal's DTR signal.  The modem responds OK.

Chapter 5--Fax Operations and Call Detection


*************
Compatibility
The Courier modem provides Group III-compatibility when combined with 
Class 1 or Class 2.0 fax software.  In addition, the modem adheres to 
the following standards.

NOTE:  The International Telecommunication Union (ITU-T) was formerly 
the International Telegraph and Telephone Consultative Committee (CCITT).

TIA/EIA-578     Service Class 1 Asynchronous Facsimile DCE Control 
                Standard
TIA/EIA-592     Service Class 2.0 Asynchronous Facsimile DCE Control 
                Standard
ITU-T V.17      14.4K/12K bps
ITU-T V.29      9600/7200 bps
ITU-T V.27 ter  4800/2400 bps
ITU-T V.21      300 bps

********************
Fax Modem Guidelines
Fax operations require facsimile-compatible software that can send or 
receive Group III faxes.  Follow the instructions in your fax software 
manual.

The modem's normal operating mode is Data mode.  If your fax software 
is typical, it automatically switches the modem to Fax mode when you 
run the program, and resets the modem to Data mode when you exit the 
program.

If you have a problem, however, and think the modem may be in the 
wrong mode, you can use one of the following AT commands to manually 
switch the modem:

        AT+FCLASS=0 (Switch to Data mode) <Enter>
        AT+FCLASS=1 (Switch to Class 1 Fax mode) <Enter>
        AT+FCLASS=2.0 (Switch to Class 2.0 Fax mode) <Enter>

If you are not sure whether the modem is in Data or Fax mode, type the 
following command.

       AT+FCLASS? <Enter>

The modem  returns a value of 0 to indicate Data mode,  1 to indicate 
Class 1 Fax mode, or 2.0 to indicate Class 2.0 Fax mode.

NOTE:  Whenever the fax modem is reset using the ATZ command, by toggling 
the DTR signal, or by turning the power off and on, the modem will be set 
to Data mode.

*****************************
Fax Mode Flow Control Setting
Many facsimile software products use software flow control when the 
modem is in Fax mode.  Throughout our documentation, we recommend that 
you use hardware flow control for Data mode (factory setting).  However, 
to allow compatibility with software products that use software flow 
control by default, U.S. Robotics fax modems now automatically change 
to software flow control when entering Fax mode.

**********
FCC Notice
FCC part 68, rules regarding fax operation, has been amended as follows:  
Telephone facsimile machines--identification of the sender of the message:  

It shall be unlawful for any person within the United States to use a 
computer or other electronic device to send any message via a telephone 
facsimile machine unless such a message clearly contains, in a margin at 
the top or bottom of each transmitted page or on the first page of the 
transmission, the date and time it is sent and an identification of the 
business, other entity, or individual sending the message and the 
telephone number of the sending machine or of such business, other 
entity, or individual.  Telephone facsimile machines manufactured on 
and after December 20, 1992 must clearly mark such identifying information 
on each transmitted page.

********************
Notes to Programmers
Lists of supported Class 1 fax commands and optional Class 2.0 commands 
are in Appendix K.

If you want to know more about the supported Class 1 fax commands, 
refer to the standard for the Service Class 1 fax protocol.

ANSI/EIA/TIA-578-1990 (EIA-578)
Asynchronous Facsimile DCE Control Standard
November, 1990   Approved:  October 22, 1990

For more information on Class 2.0, refer to the standard for the 
Service Class 2.0 fax protocol.

ANSI/EIA/TIA-592-1993 (EIA-592)
Asynchronous Facsimile DCE Control Standard
May, 1993   

You can obtain copies of these standards by contacting Global 
Engineering Documents, at 1-800-854-7179.

**************
Call Detection
Courier High Speed modems support Call Detection, which is a method of 
reporting whether an incoming call is Data, Fax Class 1, or Fax Class 2.0.  
It is especially useful for Bulletin Board systems, as it automates 
recognition of different calls from multiple users.

Call Detection is an optional Service Class 2.0 feature, and is also 
implemented by U.S. Robotics for Fax Class 1 applications.

To obtain a copy of the technical specification of U.S. Robotics' 
implementation of Call Detection for Fax Class 1, call our BBS at 
(708) 982-5092 and download the file CALLSEL.TXT.

For information on implementing Fax Class 2.0 Call Detection, see the 
standard listed above.  For a list of the optional Fax Class 2.0 
commands supported by U.S. Robotics, see Appendix K.


Chapter 6--Queries and Help Screens

*******************
User Inquiries (In)
The Inquiry command has 11 options.  The most commonly used options 
display the following information:

ATI3    Call duration 
ATI4    Current settings 
ATI5    NVRAM settings
ATI6    Link diagnostics summary


I0      The modem returns a 4-digit product code.  If you have a problem and 
        call U.S. Robotics' Technical Support Department, you may be asked 
        for this product code.

I1      The modem performs a checksum of its read-only memory (ROM) and 
        returns the result to the screen.  This function is used only in 
        factory testing.  The modem should always read the same number. 

I2      The modem performs a test of its random access memory (RAM) and 
        returns either the OK (0) or ERROR (4) result code, followed by OK 
        when the test is completed.  You may want to use this command as a 
        checkpoint if the modem appears to be malfunctioning.

I3      The modem returns the duration of the last call if set to K0.  It 
        displays the actual time if set to K1.  See the description of the 
        Kn command in Chapter 4.

I4      The modem displays its current configuration.  Figure 6.1 below 
        is an example.

Figure 6.1--Sample Result of ATI4 Command

ati4
USRobotics Courier Dual Standard V.34 Fax Settings...

   B0  C1  E1  F1  M1  Q0  V1  X1
   BAUD=57600  PARITY=N  WORDLEN=8
   DIAL=PULSE  ON HOOK   TIMER

   &A1  &B0  &C1  &D2  &G0  &H0  &I0  &K1  &L0  &M4  &N0
   &P0  &R1  &S0  &T5  &X0  &Y1  %N6  

   S00=000  S01=000  S02=043  S03=013  S04=010  S05=008  S06=002  S07=060  
   S08=002  S09=006  S10=007  S11=070  S12=050  S13=000  S14=000  S15=000  
   S16=000  S17=000  S18=000  S19=000  S20=000  S21=010  S22=017  S23=019  
   S24=150  S25=005  S26=001  S27=000  S28=008  S29=020  S30=000  S31=000  
   S32=009  S33=000  S34=000  S35=000  S36=000  S37=000  S38=000  S39=000  
   S40=000  S41=000  S42=126  S43=200  S44=015  S45=000  S46=000  S47=000  
   S48=000  S49=000  S50=000  S51=000  S52=000  S53=000  S54=000  S55=000  
   S56=000  S57=000

   LAST DIALED #:                                       

OK


I5      The modem displays the configuration stored in nonvolatile random 
        access memory (NVRAM), as in the following example.  If your 
        modem connects to a modem that has Dial Security and local access 
        enabled, you cannot view the stored phone numbers.


Figure 6.2--Sample NVRAM Settings Screen

ati5
USRobotics Courier Dual Standard V.34 Fax NVRAM Settings...

   DIAL=PULSE  B0  F1  M1  X7
   BAUD=57600  PARITY=N  WORDLEN=8

   &A3  &B1  &G0  &H1  &I0  &K3  &L0  &M4  &N0
   &P0  &R2  &S0  &T5  &X0  &Y1  %N6

   S00=001  S02=043  S03=013  S04=010  S05=008  S06=002  S07=060  S08=002
   S09=006  S10=007  S11=040  S12=050  S13=000  S15=000  S19=000  S21=010
   S22=017  S23=019  S24=150  S25=005  S26=001  S27=000  S28=008  S29=020
   S31=000  S32=009  S33=000  S34=000  S35=000  S36=000  S37=000  S38=000
   S39=000  S40=000  S41=000  S42=126  S43=200  S44=015  S51=000  S53=000
   S54=000  S55=000  S56=000  S57=000
                             STORED PHONE NUMBERS
0:                                      1:                                      
2:                                      3:                                      
4:                                      5:                                
6:                                      7:         
8:                                      9:                                     
        STORED COMMAND = 

OK

I6      During a connection, the modem monitors and stores information 
        about link operations.  When the call is ended, you can request 
        a diagnostic summary, as in the following example.  The duration 
        of the last call or real time is displayed depending on the Kn 
        setting.


Figure 6.3--Sample Link Diagnostics Screen (ATI6) 

ati6
USRobotics Courier Dual Standard V.34 Fax Link Diagnostics...

Chars sent      0       Chars Received  0
Chars lost      0
Octets sent     0       Octets Received 0
Blocks sent     0       Blocks Received 0
Blocks resent   0

Retrains Requested      0       Retrains Granted        0
Line Reversals  0       Blers           0
Link Timeouts   0       Link Naks       0

Data Compression         NONE
Equalization    Long
Fallback        Disabled
Last Call       00:00:00

Disconnect Reason is Keypress Abort
OK

For calls under data compression, the number of characters sent may be 
less than the number of octets sent, due to buffering operations.  Line 
Reversals only apply to HST-mode operations, when the modems switch the 
high and low speed channels.  At this time, online fallback is only 
reported Enabled in HST-mode.

Most terms used in the display are self-explanatory except for the 
following:

Octets:  
         Compressed data units.  If the number of octets is greater than 
         the number of characters sent, the modems probably used MNP5 
         compression on an already compressed file, and the result was 
         expanded data.  

Line Reversals:  
         The number of times HST-mode modems switched the high 
         and low speed channels.

Blers:  
         Errors in data and protocol blocks.  If there were many block 
         errors, your receiver may have experienced problems on the line.

Blocks Resent:  
         These represent blocks the remote modem resent due to 
         the previous category, Blers.

Link Timeouts:  
         Protocol detection problems:  communications were 
         severed momentarily, and the modems probably recovered.  
         This does not indicate the retry timeout.

Link Naks:  
         Negative acknowledgments (one or more blocks).

Data Compression:  
         Indicates the type of data compression negotiated 
         for the call (V42BIS or MNP5) or NONE.  A V42BIS 
         response includes the size of the dictionary and the 
         maximum string length used, for example, 2048/32.  
         See Appendix A for more information.

Equalization Long/Short:  
         Status of S15 bit 0; long if bit 0=0, short 
         if bit 0=1.  Short equalization applies 
         only to HST modems.

Fallback:  
         Enabled/Disabled:  indicates whether or not the modems 
         negotiated online fallback during the connection sequence.

Protocol:  
         indicates the error control protocol negotiated (LAPM, 
         ST, MNP, NONE) or SYNC for a synchronous call.

Speed:  
         The last rates at which the receiver/transmitter were operating 
         before disconnecting.

Disconnect Reason:  
         Possible reasons the modem hung up are as follows:

         A Rootless Tree:  
              The modem received an invalid V.42 bis (compression) 
              frame.

         Break Timeout:  
              Incompatible processing of a Break signal occurred.

         DISC:  
              The remote modem sent a V.42 Disconnect frame.

         DTR dropped:  
              The computer or terminal dropped the Data Terminal 
              Ready signal, terminating the call.

         Escape code:  
              The operator sent the modem the +++ escape code.

         Extra Stepup:  
              The modem received an invalid V.42 bis (compression) 
              frame.

         GSTN (General Switch Telephone Network) Clear Down:  
              The connection was non-ARQ and DTR was dropped from one side 
              of the connection, or the DISC frame was corrupted due to 
              noise.

         Illegal Command Code:  
              The modem received an invalid V.42 bis (compression) frame.

         Inactivity timeout:  
              The modem detected no activity on the line for 
              the duration specified in Register S19 (default is 0, 
              timer disabled).

         Invalid Codeword:  
              The modem received an invalid V.42 bis (compression) frame.

         Invalid speed:  
              The modem is set to &N1 or higher, for a fixed 
              link rate, and the remote modem is not operating at the 
              same rate.

         LD received:  
              The remote modem sent an MNP error control Link 
             Disconnect request.

         Loop loss disconnect:  
              The modem detected a loss of current on the 
              loop connecting it with the telephone company central 
              office.  This usually occurs because the remote modem has 
              hung up:  the central office drops current momentarily 
              when there is a disconnect at the other end of a call.  
              Unless Register S38 is set higher than zero, the modem 
              immediately hangs up at loop loss.

         Loss of carrier:  
              The modem detected loss of the remote modem's 
              carrier and waited the duration specified in Register 
              S10 (default is 0.7 seconds).

         MNP incompatibility:  
              The modem is set to &M5 and the remote modem 
              does not have MNP capability, or there was an MNP 
              negotiation procedure error.

         Retransmit limit:  
              The modems reached the maximum of twelve attempts 
              to transfer a data frame without error.
         
         SABME Timeout (Set Asynchronous Balance Mode Extended):  
              The modems failed this part of V.42 link negotiation. 
       
         Unable to Retrain:  
              After several attempts, disturbances on the phone 
              line prevented the modems from retraining, and they could 
              no longer transmit or receive data.

         XID Timeout:  
              The modems failed to negotiate the V.42 Detection 
              (XID Exchange) phase. 

Dial Security Disconnect Reason:  
    Possible reasons the answering modem may have hung up during a 
    Dial Security session are as follows:

    Security Abort:  
         The modem hung up because it received an invalid 
         password three times.

    Prompting Not Enabled:  
         The modem hung up because the originating 
         modem did not send an autopass password, and prompting wasn't 
         enabled.

    No Prompting in Sync:  
         The originating modem did not send an autopass 
         password, and the answering modem cannot prompt for a password 
         in any synchronous mode.

    Non-ARQ Mode:  
         The modem hung up because the originating modem was 
         set for error control and the answering modem was set for 
         non-error control.

    Mode Incompatible:  
         The modem hung up because both modems were not 
         set to the same error control setting.

    No Prompting in Non-ARQ:  
         Prompting was enabled, but the modem hung 
         up because the originating modem was set for error control, 
         and the answering modem was set for non-error control.  The 
         answering modem cannot prompt when it is set for non-error 
         control.   

I7      The modem returns a product configuration.  If you have a problem 
         and call U.S. Robotics' Technical Support staff, you may be asked 
         to read this screen.

I8      Not used

I9      Not used

I10     View Dial Security Account status.  For security administrators 
         only, unless local security is disabled, S53=0 or S53.2=0.

Figure 6.4--Sample Dial Security Account Status Screen

ati10
USRobotics Courier Dual Standard V.34 Fax

DIAL SECURITY STATUS

     DIAL SECURITY ENABLED:[N]       LOCAL SECURITY ENABLED:[N]
     PROMPTING ENABLED:[N]           FORCED AUTOPASS:[N]
    LOCAL ACCESS PASSWORD:[NO PSW]   AUTOPASS PASSWORD:[NO PSW]

ACCOUNT   PSW      ACCT/E    DIAL/B   NEW_#    PHONE #
   #0     [NO PSW]               [N]               [N]           [N]
   #1     [NO PSW]               [N]               [N]           [N]
   #2     [NO PSW]               [N]               [N]           [N]
   #3     [NO PSW]               [N]               [N]           [N]
   #4     [NO PSW]               [N]               [N]           [N]
   #5     [NO PSW]               [N]               [N]           [N]
   #6     [NO PSW]               [N]               [N]           [N]
   #7     [NO PSW]               [N]               [N]           [N]
   #8     [NO PSW]               [N]               [N]           [N]
   #9     [NO PSW]               [N]               [N]           [N]
OK


I11      Connection report used for debugging purposes.  A U.S. Robotics 
         Technical Support representative may ask you for information 
         provided on this screen.

**********************
S-Register Query (Sr?)
This command allows you to view the contents of a particular S-Register, 
as in the following example that requests the contents of Register S0 
("On what ring will the modem answer?"):

           ATS0? <Enter>

*************************
Phone Number Query (&Zn?)
At this command, the modem returns the phone number stored in NVRAM at 
position n, as in the following example that includes a sample modem 
response: 

           AT&Z3? <Enter>5551234

******************************
Last-Dialed Number Query (DL?)
At this command the modem displays the number stored in the last-dialed 
number buffer:

           ATDL? <Enter>

**********************************
Stored Command String Query (&ZC?)
At this command the modem displays the command string stored in NVRAM with 
the &ZC=s command:

          AT&ZC? <Enter>

************
HELP Screens 
Courier modems provide five Help screens:  summaries of the basic AT 
command set, extended ampersand (&) command set, Dial command options, 
S-Register functions, and percent (%) command set.  

NOTE:  The Help screens are not available when the modem makes a 
connection in synchronous mode:  &M1, &M6, or &M7.


Stop/Restart Display 
The following command stops the display. Hold down the Control key and 
type "S":

            <Ctrl>-S

To restart the display, use the same command or press any key.


Cancel Display 
Either of the following commands cancels the display. 
            <Ctrl>-C
            <Ctrl>-K

*********************
Basic Command Set ($)
At AT$, the Courier displays a screen that shows a partial summary of the 
command set.  A second screen, activated by pressing any key, shows the 
remaining commands.  The first screen is shown in Figure 6.5.

Figure 6.5--Sample Basic Commands HELP Screen 

at$
HELP,  Command Quick Reference (CTRL-S to Stop, CTRL-C to Cancel)

&$    HELP, Ampersand Commands        Kn     n=0  Call Duration Mode        
%$    HELP, Percent Commands                 n=1  Real Time Clock Mode      
A/    Repeat Last Command             Mn     n=0  Speaker Off               
A>    Continuously Repeat Command            n=1  Speaker On Until CD       
AT    Command Mode Prefix                    n=2  Speaker Always On         
A     Answer Call                            n=3  Speaker Off During Dial   
Bn    n=0  V.32 originate mode        On     n=0  Return Online              
      n=1  HST originate mode                n=1  Return Online & Retrain    
Cn    n=0  Transmitter Off                   n=2  Return Online & Speed Shift
      n=1  Transmitter On             P      Pulse Dial                     
Dn    Dial a Telephone Number         Qn     n=0  Result Codes Sent         
      n=0..9#*TPR,;"W@!()-                   n=1  Quiet (No Result Codes)   
DL    Dial Last Phone Number                 n=2  Verbose/Quiet On Answer   
DSn   Dial Stored Phone Number        Sr=n   Sets Register "r" to "n"       
D$    HELP, Dial Commands             Sr?    Query Register "r"             
En    n=0  No Command Echo            S$     HELP, S Registers              
      n=1  Echo Command Chars         T      Tone Dial                      
Fn    n=0  Online Echo                Vn     n=0  Numeric Responses         
      n=1  No Online Echo                    n=1  Verbal Responses          
Strike a key when ready . .         

*************************
Extended Command Set (&$)
At AT&$, the Courier displays a screen that shows a partial summary of the 
extended ampersand command set.  A second screen, activated by pressing 
any key, shows the remaining command set.  The first screen is shown in 
Figure 6.6.

Figure 6.6--Sample Ampersand Commands HELP Screen

at&$
HELP, Ampersand Commands (CTRL-S to Stop, CTRL-C to Cancel)

&An     n=0  Disable /ARQ Result Codes     &Nn     n=0  Highest Link Speed          
        n=1  Enable /ARQ Result Codes              n=1  300 bps                     
        n=2  Enable /Modulation Codes              n=2  1200 bps                    
        n=3  Enable /Extra Result Codes            n=3  2400 bps                    
&Bn     n=0  Floating DTE Speed                    n=4  4800 bps                    
        n=1  Fixed DTE Speed                       n=5  7200 bps                    
        n=2  DTE Speed Fixed When ARQ              n=6  9600 bps                    
&Cn     n=0  CD Always On                          n=7  12000 bps                   
        n=1  Modem Controls CD                     n=8  14400 bps                   
&Dn     n=0  Ignore DTR                            n=9  16800 bps                   
        n=1  On-Line Command Mode                  n=10 19200 bps                   
        n=2  DTE Controls DTR              &Pn     n=0  N.American Pulse Dial       
&Fn     n=0  Load Factory Configuration            n=1  UK Pulse Dial               
        n=1  Hardware Flow Control Cnfg.   &Rn     n=0  CTS Follows RTS             
        n=2  Software Flow Control Cnfg.           n=1  Ignore RTS                  
        n=3  HST/Cellular w/ HW FC Cnfg.           n=2  RX to DTE/RTS high          
&Gn     n=0  No Guard Tone                 &Sn     n=0  DSR Always On               
        n=1  550 Hz Guard Tone                     n=1  Modem Controls DSR          
        n=2  1800 Hz Guard Tone                    n=2  Pulse DSR, CTS=CD           
Strike any key when ready . . .


*************

Dialing (D$)
At ATD$, the Courier displays this Dial command summary:

Figure 6.7--Sample Dial Command HELP Screen

atd$
HELP, Dial Commands (CTRL-S to Stop, CTRL-C to Cancel)

0-9     Digits to Dial 
*       Auxiliary Tone Dial Digit
#       Auxiliary Tone Dial Digit
T       Tone Dialing
P       Pulse Dialing
R       Call an Originate Only Modem
,       Pause (Wait for S8 Time)
;       Remain in Command Mode After Dialing
"       Used to Dial Alpha Phone #'s
W       Wait for 2nd Dial Tone (X3-X7)
@       Wait for an Answer (X3-X7)
!       Flash Switch Hook

OK
 

*************************
S-Register Functions (S$)
At ATS$, the Courier displays a screen that shows a partial summary of 
the S-Register functions.  More screens, activated by pressing any key, 
show the remaining registers.  The first screen is as follows.

Figure 6.8--Sample S-Register HELP Screen

ats$
HELP, S Register Functions (CTRL-S to Stop, CTRL-C to Cancel)

S0  Ring to Answer On                 S33 Reserved                           
S1  Counts # of Rings                 S34 Bit Mapped                         
S2  Escape Code Char                        1 = Disable V32bis               
S3  Carriage Return Char                    2 = Disable Enhanced V32 mode    
S4  Line Feed Char                          4 = Disable Quick V32 retrain    
S5  Backspace Char                          8 = Enable V23 Fallback          
S6  Wait Time/Dial Tone (sec)              16 = Change MR to DSR             
S7  Wait Time/Carrier (sec)                32 = Enable MI/MIC                
S8  Comma Time (sec)                       64 = Disable RA Busy Msg          
S9  Carrier Detect Time (1/10sec)         128 = Disable Terbo          
S10 Carrier Loss Time (1/10sec)       S35 Reserved                           
S11 Dial Tone Spacing (msec)          S36 Reserved                           
S12 Escape Code Time (1/50sec)        S37 Reserved                           
S13 Bit Mapped                        S38 Disconnect Wait Time (sec)         
    1 = Reset On DTR Loss             S39 Reserved                           
    2 = Do Originate in Auto Answer   S40 Reserved                           
    4 = No Pause Before Result Codes  S41 # of Allowed Login Attempts     
    8 = Do DS0 On DTR                 S42 Remote Escape Code Char     
    16 = Do DS0 On Reset              S43 Remote Escape Code Time (1/50sec)
Strike a key when ready . . .    


*********************
Percent Commands (%$)
At AT%$, the Courier displays a screen that shows a partial summary of 
the percent command functions.  A second screen, activated by pressing 
any key, shows the remaining registers.  The first screen is as follows.

Figure 6.9--Sample Percent HELP Screen

at%$
HELP, Percent Commands (CTRL-S to Stop, CTRL-C to Cancel)

%An=  Security Account Information   %Fn    Remote DTE Data Format       
      Command Structure                     n=0  8, No parity                   
%An=  PW,ACCT E,DIAL B,NEW#,PH#             n=1  7, Mark parity                   
      n = (0-9)                             n=2  7, Odd parity                   
      PW = Password                         n=3  7, Even parity                   
      ACCT E = Account Enable        %L=PWn Security Local Access Psw   
      DIAL B = Dial Back Enable             PWn = (0-9)               
      NEW# = New Dial Back #         %Nn    V.25bis Synchronous Clock Rate
      PH# = Dial Back Phone #               n=0  RESERVED               
%Bn   Remote DTE Data Rate                  n=1  RESERVED               
      n=0    110  bps                       n=2   1200 bps               
      n=1    300  bps                       n=3   2400 bps               
      n=2    600  bps                       n=4   4800 bps               
      n=3   1200  bps                       n=5   7200 bps               
      n=4   2400  bps                       n=6   9600 bps               
      n=5   4800  bps                       n=7  12000 bps               
      n=6   9600  bps                       n=8  14400 bps               
      n=7  19200  bps                       n=9  16800 bps               
      n=8  38400  bps                       n=10 19200 bps               
Strike a key when ready . . .      


Appendix A--Link Negotiation (Handshaking) and Error Control


This appendix includes information on how U.S. Robotics modems  
negotiate with remote modems for the rate and other characteristics 
of each connection.   In addition, you'll find information on error 
control and, especially useful, some statistics and guidelines on 
using the modem for the best throughput.

Some of the following text includes the term ARQ, which means Automatic 
Repeat Request.  ARQ is a method used in many error control protocols to 
ensure that any data that has been corrupted in transit is retransmitted.  
We use the term in our documentation to designate a connection under 
error control.

NOTE:  High speed calls are highly vulnerable to errors unless the 
data is protected by error control.  The V. protocol operations 
described below take place even if one of the modems is not set for 
error control, thereby prohibiting error control for the call.  
If your modem connects with a modem at high speed but without error 
control, and if you are not using an error control protocol for 
your call, you may lose data.    

Dual Standard modems in HST mode, in contrast, are unable to connect 
with other HST modems at higher than 2400 bps, unless error control 
is negotiated for the call.  
 
****************
V.34 Handshaking
The Courier defaults to V.34 and tries for the highest possible speed 
when it attempts to connect with another modem, 28.8K bps.  The entire 
V.FC range comprises 28.8K, 26.4K, 24K, 21.6K, 19.2K, 16.8K, 14.4K, 
9600, 7200, 4800, and 2400 bps.   If the remote modem is not V.34 
capable, a connection is made using the highest compatible modulation 
scheme (V.FC, V.32 terbo, V.32 bis, and so on, down to as low as Bell 
103, or 300 bps). 

If the remote modem has V.34 capability, the two modems use a line 
probing technique to determine the highest speed possible under 
current line conditions, and complete the connection.  If the remote 
modem does not have V.34 capability, a calling Courier modem listens 
to the other modem's answer tones to identify what standard rate the 
remote modem is operating at, and adjusts to that rate.  An answering 
Courier modem sends out a series of answer tone signals until both modems 
can negotiate the best connection rate.

******************************** 
V. Fast Class (V.FC) Handshaking
The Courier defaults to V.Fast Class and tries for the highest 
possible speed when it attempts to connect with another modem, 
28.8K bps.  The entire V.FC range comprises 28.8K, 26.4K, 24K, 
21.6K, 19.2K, 16.8K, and 14.4K bps.   If the remote modem is not 
V.FC capable, a connection is made using the highest compatible 
modulation scheme (V.32 terbo, V.32 bis, and so on, down to as 
low as Bell 103, or 300 bps). 

If the remote modem has V.FC capability, the two modems use a line 
probing technique to determine the highest speed possible under 
current line conditions, and complete the connection.  If the 
remote modem does not have V.FC capability, a calling Courier modem 
listens to the other modem's answer tones to identify what standard 
rate the remote modem is operating at, and adjusts to that rate.  An 
answering Courier modem sends out a series of answer tone signals 
until both modems can negotiate the best connection rate.
 
****************************************************
U.S. Robotics V.32 terbo to U.S. Robotics V.32 terbo
On these connections, Couriers have two features that result in 
outstanding performance:  Quick Connect and Adaptive Speed Leveling 
(ASL).  

Quick Connect allows the modems to connect in approximately 7 seconds, 
a far shorter time than normal with most modems.  

ASL (described below in Other V.Protocol Operations) is used by U.S. 
Robotics modems operating in V.32 terbo and V.32 bis modes.

****************************
Other V. Protocol Operations
Earlier, lower-speed V. protocols do not employ line probing.  Instead,  
they use predefined answer tones to specify, or identify, speed 
capabilities.  These protocols define the following maximum speeds.

*  V.32 terbo:  19.2K bps, with an additional Courier-to-Courier 
   speed of 21.6K bps.
*  V.32 bis:  14.4K bps.
*  V.32:  9600 bps.

ASL (used in V.32 terbo and V.32 bis modes) is a strategy that allows 
the modems' receivers and transmitters to act independently of each 
other.  We have always featured a fallback/fall forward feature with 
error-correcting modems that allows them to slow down if there are 
problems with the phone line, in order to avoid data errors, and then 
speed up again.  But the independence of the receiving and transmitting 
channels means that one channel or the other may slow down and then speed 
up, without affecting the data flow on the other.  The result is more 
efficient line operation. 

WARNING:  Answering V.32 terbo modems shift their serial port rate up 
to 38.4K (for 21.6K connections) if the calling V.32 terbo modem dials 
in at 21.6K.  The answering V.32 terbo modem then sends data to its 
computer at 38.4K bps.   V.32 bis modems shift their serial port rate 
to 19.2K bps in order to make 14.4K bps connections.  If your ocomputer 
or terminal does not support these higher serial port rates, you need 
to disable V.32 terbo and/or V.32 bis.  See Appendix B, Register S34.

NOTE:  While many modems on the market now use the more efficient 
speeds, there may be a problem in answering older, "dumb" V.32 
modems at 9600 bps.  Register S28 is used to modify the duration 
of the extra tones used in V.32 negotiations, in the rare instance 
that this may be necessary.  See S-Registers, in Appendix B.

*************************
Dual Standard Handshaking
We  recommend that Dual Standard modems be set to retain the default 
B0 and &N0 settings.  This allows them to connect with V. protocol 
modems and HST modems in both Originate and Answer modes at a variety 
of speeds.  

An originating Dual Standard modem set to B1 sends out a Bell answer 
tone, which is the prevalent standard in the U.S. and Canada for 
connections at 2400 bps and lower.   At higher speeds, the Dual 
Standard also recognizes the ITU answer tones necessary for 
connecting with V. protocol modems, and adjusts to the answering 
modem.  

However, in Answer mode, a Dual Standard modem sending out the Bell 
answer tone (B1) won't be recognized by V. protocol modems.  The 
calling V. protocol modem, instead, will wait until it detects a 
tone it recognizes, the V.22 bis tone used at 2400 bps.   If you 
wish to have your Dual Standard connect with V. protocol modems at 
high speeds, make sure it is set to B0 for the ITU answer tones.  
It will also connect with HST modems at speeds up to 16.8K bps.
 
****************************
Error Control and Throughput

Error control is available for calls at 1200 bps and above.  It can be 
disabled, although high speed calls (above 2400 bps) should always 
be under error control.  The operations defined in an error control 
protocol include the following:

*  Establishment of compatibility 
*  Data frame formatting
*  Error detection through Cyclic Redundancy Checking (CRC)
*  Retransmission of corrupt data frames

The Courier is set at the factory to &M4, causing it to try for an error 
control connection and, if that isn't possible, to proceed with the call 
in Normal mode.  The modem first tries for a V.42 connection, then an 
MNP connection.  The following information is based on the Courier's 
setting of &M4.

****************
V.42 Handshaking
This international standard includes a two-stage handshaking process: 

*  A Detection phase that is based on an exchange of predefined characters.  
*  LAPM (Link Access Procedures for Modems) Negotiation.  In this phase, 
   the modems identify their capabilities concerning maximum data block 
   size and the number of outstanding data blocks allowed before an 
   acknowledgment is required.
 
***************
MNP Handshaking
This protocol is supported by the ITU-T V.42 Recommendation.  It was 
originally developed by Microcom, Inc. and is now in the public domain.  

MNP is based on special protocol frames.  If the remote modem doesn't 
recognize an MNP Link Request, error control isn't possible. (In HST 
asymmetrical mode, U.S. Robotics modems use a proprietary scheme 
similar to MNP.)
 
****************
Data Compression
If the modems successfully establish a V.42 connection, they also negotiate 
for V.42 bis data compression.  If they successfully establish an MNP 
connection, they negotiate for MNP5 data compression.  The type of 
compression for a call, if any, is reported in the ATI6 display, and 
in the CONNECT message if the modem is set to &A3.

Modems using V.42 bis compression negotiate the following options and 
report them in the ATI6 display.

*  Dictionary size, that is, the amount of memory available for compression 
   table entries.  (Entries are codes devised for redundant data.  The 
   data is packed into shorter data units, called code words, and unpacked 
   by the receiving modem.)

   Possible sizes are as follows:  
         Bits    Entries
         9       512
         10      1024
         11      2048

   U.S. Robotics modems use 11-bit, or 2048-entry dictionary, but drop down 
   if the remote modem uses a 9- or 10- bit dictionary.  The size of the 
   dictionary for a call is reported in the ATI6 display.

*  Maximum string length of each entry.  As the dictionary fills, the 
   modem deletes the oldest unused strings.

V.42 bis compression is more efficient than MNP5 compression in part 
because it dynamically deletes entries that are no longer used.  In 
addition, it works better with files that are already compressed. 
These include .ZIP files downloaded from many Bulletin Boards and 
8-bit binary files, which seem to the modem to be compressed.  
   
MNP5 compression should not be used with such files because it adds data 
to them, which lessens throughput.  (The additional data is stripped when 
the file is decompressed by the remote modem.)  When transferring 
such files, it's best to set the modem to &K3:  this allows V.42 bis 
compression to work dynamically with the compressed data, but disables 
MNP5.
 
************
Flow Control
Flow control of data from the computer is required under error control 
for two reasons:

1. The transmitting modem buffers a copy of each frame it transmits to 
   the remote end until it is acknowledged by the receiving modem.

2. If errors are encountered, retransmission activity can cause a 
   steady stream of data from the computer to overflow the buffer. 

*********************
Throughput Guidelines 
The following guidelines should help to make the most of the modem's 
advanced performance features.  In many instances, experimentation 
and experience will indicate what works best for your applications.

1. Optimal throughput is attained under the following conditions:
   
   *  The communications software allows fixing the serial port rate 
      higher than the connection rate, by setting the software to 
      115.2K, 57.6K, or 38.4K bps and setting the modem to &B1.

      If the software automatically switches serial port rates to follow 
      the connection rate, the modem's serial port rate must be also set 
      to follow the connection rate for each call, &B0, and throughput 
      will be limited. 

      Installations with specialized software may want to enable a fixed 
      serial port rate for ARQ calls and a variable serial port rate for 
      non-ARQ calls.  See the &B2 command in Chapter 4.

   *  The call is under data compression.  
   
   *  The data is comprised of text files rather than binary files such 
      as .EXE or .COM files.  See the table at the end of this appendix. 

2. MNP5 compression is disabled for files that are already compressed, 
   and 8-bit binary files that appear to the modem to be already compressed.  
   MNP5 is disabled by setting the modem to &K3. 

3. The file transfer is not slowed down by a file-transfer protocol.  
   Many non-text files require a file transfer protocol, but the results 
   vary.  For example, certain public domain file transfer protocols 
   have the following effects:

   Kermit  Newer versions support packets up to 9K and a sliding window 
           design to eliminate turn-around delay.  With earlier versions, 
           however, throughput may be severely reduced due to short block 
           lengths (possibly under 128 bytes) and acknowledgment 
            turnaround time.

   Xmodem  Throughput may be reduced if your version uses short block 
           lengths (128 bytes).  Some versions use larger blocks 
           (1K blocks).  Throughput is also reduced by overhead (error 
           control protocol information).

   Ymodem  There is an improvement over Xmodem, due to larger block 
           lengths (1K bytes), but throughput is still reduced by the 
           protocol's error control overhead.

   The above protocols further reduce throughput when an error control 
   connection is established.  The accuracy of the data is checked both 
   by the file transfer protocol and the modem.  To avoid redundancy, 
   use the above protocols only for non-ARQ connections, and only at 
   speeds of 2400 bps and below.  
   
   For the best throughput, but on error-controlled connections only and 
   with hardware flow control, we recommend the most current version of 
   Zmodem.  Overhead is minimal with this protocol, with throughput 
   almost equal to that obtained with no file-transfer protocol.  Zmodem 
   should also be used for non-ARQ connections.  Leave the modem at its 
   &M4 and &K1 settings for both error control and data compression.  
   Ymodem-G is another good choice, but never without both the local 
   and remote modems using error control:  if Ymodem-G detects an error, 
   it aborts the transfer.  Do not use either protocol with software flow 
   control (XON/XOFF signaling).
 
******************
Typical Throughput
The maximum connection rate between two V.34 modems is 28.8K bps.  
Ocassionally, connections occur at 26.4K, 24K, and 21.6K bps because 
line quality differs from location to location  Line conditions and 
data rate affect throughput.  Also remember, your serial port rate 
must match or exceed your connection rate.  If you set your serial port 
rate at 19.2K bps, the V.34 modem will only connect at or below 19.2K bps.

The tables below indicate the typical throughput, in characters per 
second (cps), that can be expected under the following conditions.  

*  Connection (link) rates of 14.4K, 21.6K, and 28.8K bps, respectively
*  Serial port rates set at 57.6K bps for the 14.4K bps connection and 
   115.2K bps for the 21.6K and 28.8K bps connections
*  Modem set to &B1 (fixed serial port rate)
*  V.42 bis compression negotiated for the call, and the default size 
   11-bit, 2048-entry dictionary
*  Straight data (not already compressed, no file-transfer protocol)
*  Transmission from a fast (486) computer

NOTE:  .ZIP files that are already compressed or files that appear to 
the modem to be compressed yield lower throughput.  We recommend 
setting the modem to &K3 when transferring these files, to allow V.42 
bis but disable MNP5.   

14.4K bps
   File Type       Typical throughput (cps) 
   
   Text file       3400
   .ZIP files      1600
   Database files  4600
   Graphic files   2900

21.6.4K bps
   File Type       Typical throughput (cps) 
   
   Text file       5100
   .ZIP files      2400
   Database files  7200
   Graphic files   4300

28.8K bps
   File Type       Typical throughput (cps) 
   
   Text file       6800
   .ZIP files      3200
   Database files  9600
   Graphic files   5800

Appendix B--Summaries and Tables

CONTENTS
	 The RS-232 Interface, with Pin Definitions
	 Front Panel Indicators
	 DIP Switch Summary
	 Default Settings
	 S-Register Summary
	 ASCII Chart


********************
THE RS-232 INTERFACE

***********
Description
The RS-232 interface is a standard developed by the Electronic 
Industries Association (EIA).  It defines the signals and voltages 
used when data is exchanged between a computer or terminal and a 
modem or serial printer.  Data is transmitted between the devices 
via a cable with 25-pin, 9-pin, 8-pin or custom-built connectors.

The modem takes a DB-25P (25-pin plug, or male) connector at one 
end of the cable.  Computer equipment varies, however.  Check the 
serial port at the rear of your machine, which may be labeled serial, 
comm port, or some other term (e.g., RS-232).  If there are no labels, 
review your machine documentation to find out which is the serial port.  
(There may be more than one.)  Don't use a port marked parallel, 
printer or aux.  

The physical serial port on the computer or terminal will be either a 
socket (female) or plug (male) that typically accommodates 25 or 9 
pins.  For example, the port on the IBM PC, PC/XT and most compatibles 
requires a DB-25S (socket) connector, while the port on the IBM PC/AT 
and some compatibles requires a DB-9S connector.  Apple computers 
require a DB-25P, DB-9P or, more typically, an 8-pin round plug connector.  
Check your computer documentation or with your computer dealer.

***************
Pin Assignments
The entire standard covers many more functions than are used in most 
data communications applications.  Pin assignments are factory set 
in the Courier to match the standard DB-25 assignments in the 
following table.  DB-9 connectors for AT-compatible computers 
should be wired at the computer end of the cable as shown in the 
DB-9 column.  If you're using an Apple computer, we strongly recommend 
that you purchase a Hardware Handshaking cable to get the highest 
possible reliability performance. 

	 Table B.1--RS-232 Interface Pin Definitions    

						 Signal Flow     
						 Computer
     DB-25   DB-9    Circuit Function            to Modem          
     
     1       _       AA  Chassis Ground          both directions
     2       3       BA  Transmitted Data        to modem
     3       2       BB  Received Data           to computer
     4       7       CA  Request to Send         to modem
     5       8       CB  Clear to Send           to computer
     6       6       CC  Data Set Ready          to computer
     7       5       AB  Signal Ground           both directions
     8       1       CF  Carrier Detect          to computer     
     12      _       SCF Speed Indicate          to computer
     15      _       DB  Synchronous TX* Timing  to computer
     17      _       DD  Synchronous RX* Timing  to computer
     20      4       CD  Data Terminal Ready     to modem
     22      9       CE  Ring Indicate           to computer
     24      _       DA  Synchronous TX* Timing  to modem

  * Indicates Transmitter (TX) or Receiver (RX)
	
*******************
Minimum Requirements
Some computer/terminal equipment supports only a few of the RS-232 signal 
functions set in the Courier.  The minimum required for the modem to 
operate are as follows: 
  
Asynchronous Calls
       DB-25   DB-9    
       Pin     Pin     Function                        
	2       3       Transmitted Data
	3       2       Received Data
	7       5       Signal Ground
	20      4       Data Terminal Ready*

   * Required only if you have the Data Terminal Ready Operations 
     switch OFF (DIP switch 1 OFF).

Synchronous Calls
You will need all of the above functions as well as pin 15 for 
Transmitter timing signals, and pin 17 for Receiver timing signals.  
You may need pin 24, which is assigned the external timing source, 
rather than the internal (modem) source assigned to pin 15.  See 
Appendix F for more detailed information.

Additional Flow Control Functions
If your computer and software support Clear to Send and you wish to use 
Transmit Data hardware flow control (&H1), Pin 5 (DB-25) or Pin 8 (DB-9) 
is required.  

If your computer and software support Request to Send and you wish 
to use Received Data hardware flow control (&R2), Pin 4 (DB-25) or 
Pin 7 (DB-9) is required.

***********************************
For 38.4K or Higher Serial Port Rate 
Your terminal or computer and software must support the 115.2K, 57.6K, or 
38.4K bps rate.  Make sure the RS-232 cable is shielded.  Cables are 
normally six feet long, but longer lengths are possible.  If you 
encounter problems with signal degradation, try a shorter cable.

If you decide to build your own cable, use a low-capacitance cable.  
To further minimize the capacitance, connect only those functions 
(pins) that your application requires.


FRONT PANEL INDICATORS
	 Symbol  Meaning            Status

	 HS      High Speed         All calls above 2400 bps:  ON during call 
				    progress, after completion of dialing; OFF 
				    during HST-mode link negotiations at 2400 
				    bps, then ON during connection.  Remains 
				    ON after disconnect until next call is 
				    originated or answered, or the modem 
				    is reset. 

	 AA      Auto Answer/       Answer mode only:  ON when your modem is 
		  Answer            in Auto Answer mode, and when answering a 
				    call; in HST-mode, goes OFF if the channel 
				    is reversed and your answering modem 
				    transmits at 450 or 300 bps.  Also goes 
				    OFF when the modem originates a call.  
				    Flashes ON for incoming ring detect.

	 CD      Carrier Detect     ON if DIP switch 6 is OFF (factory 
				    setting) and the Courier receives a valid 
				    data signal (carrier) from a remote modem, 
				    indicating that data transmission is 
				    possible.  Also ON when the CD override 
				    is on, DIP switch 6 ON.  

	 OH      Off Hook           ON when the Courier takes control of the 
				    phone line to establish a data link.

	 RD      Received Data      Flashes when the modem sends result codes 
				    or passes received data bits to the 
				    computer or terminal.  

	 SD      Send Data          Flashes when the computer or terminal 
				    sends a data bit to the Courier.

	 TR      Data Terminal      ON if DIP switch 1 is OFF (factory 
		   Ready            (setting) and the modem receives a DTR 
				    signal from the computer or terminal.  
				    Also ON when the DTR override is on, DIP 
				    switch 1 ON.

	 MR      Modem Ready/       ON when the Courier is powered on. 
		 Test Mode          Flashes when the modems retrain, including 
				    online fallback, or while the modem is in 
				    Test mode.

	 RS      Request to        ON if your terminal or software supports 
		   Send            RTS and sends the RTS signal.  OFF if the 
				    Courier is set to &R2 (Received Data 
				    hardware flow control) and the computer or 
				    terminal lowers RTS.

	 CS      Clear to Send      ON until the modem lowers CTS when 
				    Transmit Data hardware flow control is 
				    enabled (&H1, &H3).  Always ON during 
				    synchronous connections. 

	 SYN     Synchronous        ON when the modem is set to &M1, &M6,
		    Mode            &M7 and enters synchronous mode.  Flashes 
				    when Dial Security is in operation.

	 ARQ/    Error Control/     Data Mode:  Automatic Repeat Request.  ON 
	 FAX                        Fax Operations  when the Courier is set to 
				    &M4 or &M5 and successfully connects with 
				    another modem under error control.  
				    Flashes randomly when the Courier 
				    retransmits data to the remote modem.
				    Fax Mode:  Flashes steadily to indicate 
				    fax mode.


******************
DIP SWITCH SUMMARY 


The DIP switches, located at the rear of the modem, are for adapting the 
modem to your equipment and personal requirements.  If necessary, review 
your software documentation.
Some users are able to move a single switch with a finger tip.  If this 
doesn't work for you, use a toothpick or other small instrument.  Do not 
use a lead pencil.

OPERATIONS
The DIP switch settings are power-on defaults, read by the Courier when 
it is turned on.  If changed when the modem is on, switches 1-7, and 9 
require the ATZ (software reset) command to initiate the new settings.  
If you've set switch 8 OFF to disable command recognition, and want to 
return the modem to Smart mode so that it responds to commands, just 
reset switch 8 to ON.

When you issue the ATZ command, the modem reads its DIP switch settings 
and resets either to its defaults (DIP switch 10 OFF) or factory settings 
(DIP switch 10 ON).

		 Factory
	 Switch  Setting    Function                                        
	 1       OFF        Data Terminal Ready Operations 
			    OFF     Normal DTR operations:  computer must 
				    provide DTR signal for modem to accept 
				    commands; dropping DTR terminates a call
			    ON      DTR always ON (Override)

	 2       OFF        Verbal/Numeric Result Codes
			    OFF     Verbal (word) results
			    ON      Numeric results

	 3       ON         Result Code Display
			    OFF     Results suppressed
			    ON      Results enabled

	 4       OFF        Command Mode Local Echo
			    OFF     Keyboard commands displayed
			    ON      Echo suppressed

	 5       ON         Auto Answer 
			    OFF     Modem answers on first ring
			    ON      Auto answer disabled

	 6       OFF        Carrier Detect Operations
			    OFF     Courier sends CD signal when it connects 
				    with another modem, drops CD on disconnect
			    ON      CD always ON (Override)

	 7       OFF        Auxiliary, DIP Switch 3 ON
			    OFF     Result codes in Originate and Answer mode
			    ON      Result codes in Answer mode disabled

	 8       ON         AT Command Set Recognition
			    OFF     Command recognition disabled (Dumb mode)
			    ON      Recognition enabled (Smart mode)

	 9       OFF        Escape Code (+++) Response
			    OFF     Modem hangs up, returns to Command mode, 
				    sends NO CARRIER result
			    ON      Modem maintains connection, returns to 
				    Command mode, sends OK result

	 10      OFF        Power-on and ATZ Reset Software Defaults
			    OFF     Load from nonvolatile memory (NVRAM)
			    ON      Load factory settings from read only 
				    memory (ROM)

****************
DEFAULT SETTINGS

USER-PROGRAMMABLE DEFAULTS
You can create your own default configuration and store it in nonvolatile 
random access memory (NVRAM) using the &W command described in Chapter 4.  
As long as DIP switch 10 is OFF when you power on the modem, your defaults 
are loaded into the modem's random access memory (RAM).  To view your NVRAM 
settings at any time, use the ATI5 command.

Tables on the next several pages list the options you can store in NVRAM, 
including S-Register settings.  If DIP switch 10 is ON at power-on, the 
factory template 0 settings are loaded instead.  The modem has four factory 
setting templates (&F0-F3).  By default, the first time the modem is turned 
on, the modem loads the settings stored in NVRAM, which are the same as 
the settings in factory template 1 (&F1).

The following command example substitutes several user-defined defaults 
for factory settings.  The modem also stores the rate, word length and 
parity it detects from the AT command prefix.

	 AT X1 &B0 &M5 &H0 M3 &W <Enter>

The modem is shipped with DIP switch 10 OFF, so when it is powered on it 
loads the settings from NVRAM.  Until these settings are changed, they are 
the same as the settings permanently stored in factory settings template 1 
(&F1).  You can alter any of these settings, create your own power-on 
defaults, and then save them with the &W command.  See Chapter 4.  

Table B.3--&F1 Hardware Flow Control Default Template

NVRAM Options                    Setting   Description
Handshake option                   B0      ITU-T answer sequence
Error control/sync                 &M4     Normal/error control
Data compression                   &K1     Enabled
Transmit data hardware             &H1     Hardware flow control

Rec'd data hardware flow control   &R2     Enabled
Rec'd data software flow control   &I0     Disabled
Serial port rate select            &B1     Serial port rate fixed higher 
					   than connect rate
Link rate select                   &N0     Variable 

Result code subset                 X7      Extended.  Includes all codes                           
					   except VOICE
Protocol response codes            &A3     Full protocol codes
Tone/Pulse dialing                 P       Pulse dial
Online local echo                  F1      Disabled
Speaker control                    M1      ON during dial through connect

Remote Digital Loopback (RDL)      &T5     Deny RDL
Normal/Leased/Cellular line        &L0     Normal phone line
Data Set Ready operations          &S0     Override enabled
Break handling                     &Y1     Clear buffer, send immediately

Stored telephone number           &Z0-9=0  Blank
Pulse dial make/break ratio       &P0      U.S./Canada
Guard tone                        &G0      U.S./Canada

Word length*               8
Parity* 0                  None
DTE rate* (Kbps)           19.2    _

*  Detected by the modem from the AT prefix of the &W command that 
   writes your defaults to NVRAM.  Set your software to the desired word 
   length, parity, and serial port rate defaults before sending the modem 
   the AT . . . &W string.



Table B.4--&F2 Software Flow Control Template

NVRAM Options                  Setting     Description
Handshake option                  B0       ITU-T answer sequence
Normal/error control/sync         &M4      Normal/error control
Data compression                  &K1      Enabled
Transmit data flow control        &H2      Software flow control

Rec'd data hardware flow control  &R1      Disabled
Rec'd data software flow control  &I2      Enabled
Serial port rate select           &B1      Serial port rate fixed higher 
					   than connect rate
Link rate select                  &N0      Variable 

Result code subset                X7       Extended.  Includes all codes    
					   except VOICE
Protocol response codes           &A3      Full protocol codes
Tone/Pulse dialing                P        Pulse dial
Online local echo                 F1       Disabled
Speaker control                   M1       ON during dial through connect

Remote Digital Loopback (RDL)     &T5      Deny RDL
Normal/Leased/Cellular line       &L0      Normal phone line
Data Set Ready operations         &S0      Override enabled
Break handling                    &Y1      Clear buffer, send immediately

Stored telephone number          &Z0-9=0   Blank
Pulse dial make/break ratio      &P0       U.S./Canada
Guard tone                       &G0       U.S./Canada    

Word length*            8
Parity* 0               None
DTE rate* (Kbps)        19.2    _

*  Detected by the modem from the AT prefix of the &W command that writes 
   your defaults to NVRAM.  Set your software to the desired word length, 
   parity, and serial port rate defaults before sending the modem the 
   AT . . . &W string.




Table B.5--&F3 HST Cellular Template

NVRAM Options                  Setting     Description
Handshake option                  B1       HST-mode/Bell answer tone
Normal/error control/sync         &M4      Normal/error control
Data compression                  &K1      Enabled
Transmit data flow control        &H1      Hardware flow control

Rec'd data hardware flow control  &R2      Enabled
Rec'd data software flow control  &I0      Disabled
Serial port rate select           &B1      Serial port rate fixed higher 
					   than connect rate
Link rate select                  &N0      Variable 

Result code subset                X7       Extended.  Includes all codes                           
					   except VOICE.

Protocol response codes           &A3      Full protocol codes
Tone/Pulse dialing                P        Pulse dial
Online local echo                 F1       Disabled
Speaker control                   M1       ON during dial through connect

Remote Digital Loopback (RDL)     &T5      Deny RDL
Normal/Leased/Cellular line       &L2      HST Cellular
Carrier loss wait time            S10=30   Waits 3 seconds before hanging up
Data Set Ready override           &S0      Enabled
Break handling                    &Y1      Clear buffer, send immediately

Stored telephone number           &Z0-9=0  Blank
Pulse dial make/break ratio       &P0      U.S./Canada
Guard tone                        &G0      U.S./Canada

Word length*            8
Parity* 0               None
DTE rate* (Kbps)        19.2    _

*  Detected by the modem from the AT prefix of the &W command that writes 
   your defaults to NVRAM.  Set your software to the desired word length, 
   parity, and serial port rate defaults before sending the modem the 
   AT . . . &W string.


If DIP switch 10 is ON when the modem is powered on, or you load factory 
template 0 (&F0), the following settings take effect.  


Table B.6--&F0 No Flow Control Low Performance Template

NVRAM Options                   Setting    Description
Handshake option                  B0       ITU-T answer sequence
Normal/error control/sync         &M4      Normal/error control
Data compression                  &K1      Enabled
Transmit data flow control        &H0      Disabled

Rec'd data hardware flow control  &R1      Disabled
Rec'd data software flow control  &I0      Disabled
Serial port rate select           &B0      Detect from AT command: variable 
					   rate 
Link rate select                  &N0      Variable 

Result code subset                X1       Basic
Error-control response codes      &A1      Enabled
Tone/Pulse dialing                P        Pulse dial
Online local echo                 F1       Disabled
Speaker control                   M1       ON during dial through connect

Remote Digital Loopback (RDL)     &T5      Deny RDL
Normal/Leased/Cellular line       &L0      Normal phone line
Data Set Ready operations         &S0      Override enabled
Break handling                    &Y1      Clear buffer, send immediately

Stored telephone number           &Z0-9=0  Blank
Pulse dial make/break ratio       &P0      U.S./Canada
Guard tone                        &G0      U.S./Canada

Word length*              7
Parity* 1                 Even
DTE rate* (bps)           9600    

*  Detected by the modem from the AT prefix of the &W command that writes 
   your defaults to NVRAM.  Set your software to the desired word length, 
   parity, and serial port rate defaults before sending the modem the 
   AT . . . &W string.




Table B.7--NVRAM Options

							    Factory 
   NVRAM S-Register Options                                 Setting
   S0      Auto Answer                                        1
   S2      Escape code character                              43
   S3      Carriage Return character                          13
   S4      Line Feed character                                10
   S5      Backspace character                                8
   S6      Dial wait-time, sec.                               2
   S7      Carrier wait-time, sec.                            60
   S8      Dial pause, sec.                                   2
   S9      Carrier Detect time, 1/10th sec.                   6
   S10     Carrier loss wait-time, 1/10th sec.                7
   S11     Tone duration, spacing, msec.                      70
   S12     Escape code guard time, 1/50th sec.                50
   S13     Bit-mapped functions*                              0
   S15     Bit-mapped functions*                              0
   S19     Inactivity/hang up timer                           0
   S21     Break length, 1/100th msec.                        10
   S22     XON character                                      17
   S23     XOFF character                                     19
   S24     Pulsed DSR duration, 2/100th sec.                  150
   S26     RTS/CTS delay time, 1/100th sec.                   1
   S27     Bit-mapped functions*                              0
   S28     V.32 handshake time, 1/10th sec.                   8
   S29     V.21 handshake time, 1/10th sec.                   20
   S32     Voice/Data Switch Options                          9
   S33     Bit-mapped functions*                              0
   S34     Bit-mapped functions*                              0
   S38     Disconnect wait time, sec.                         0
   S41     Allowable remote login attempts                    0
   S42     Remote Access ASCII character                      126
   S43     Remote guard time, 1/50th sec.                     200
   S44     Re-establish leased-line connect, sec.             15
   S51     Bit-mapped functions*                              0
   S53     Bit-mapped functions*                              0
   S54     Bit-mapped functions*                              0
   S55     Bit-mapped functions*                              0
   S56     Bit-mapped functions*                              0
   S57     Bit-mapped functions*                              0

   *  Bit-mapped registers have up to eight functions.  See 
      descriptions later in this appendix or a briefer summary in the 
      Quick Reference Card.



******************
S-REGISTER SUMMARY

USAGE 
The default values are those users typically require.  Change the settings 
of an S-Register with the ATSr=n command, where r is the register and n 
is a decimal value from 0-255:

	     ATS13=8 <Enter>

The modem does not perform a value-range check.  Some values you select may 
not work with some equipment, and you'll have to readjust the settings.  

Some registers (S13, S14, S15, S16, S27, S34) are bit-mapped (bits 0-7).  
For example, turning on bit 0 of S13 causes the modem to reset each time 
the computer or terminal drops its Data Terminal Ready (DTR) signal.  
Turning on bit 3 of S13 causes the modem, on receipt of DTR, to auto 
dial the number stored at position 0 in NVRAM.

To turn on one or more bits in any bit-mapped register, use the total of 
the values shown below.  For example, S13=9 turns on bits 0 (value of 1) 
and 3 (value of 8).

Alternatively, identify the bits to be turned on with the following format:  
Sr.b=1, where r is the register and .b is the bit.  This format does not 
require knowledge of the bit's value.  S13.0=1 .3=1 is the equivalent of 
S13=9, above.  To turn off a bit function, set it to zero:  S13.0=0.

To display the contents of a register, use ATSr? as in this example: 

	     ATS19? <Enter>

       
Register    Default     Function                                
S0          See DIP     Sets the number of rings on which to
	    Switch 5    answer when in Auto Answer mode.  S0=0 disables 
			Auto Answer, the same as DIP switch 5 ON (factory 
			setting).  S0=1 enables Auto Answer and the modem 
			answers on the first ring. 

			NOTE:  If DIP switch 5 is OFF and S0=0, 
			Auto Answer remains disabled.

S1           0          Counts and stores the number of rings from an 
			incoming call. 

S2           43         Stores the ASCII decimal code for the escape code 
			character.  Default character is “+”.  A value of 
			128-255 disables the escape code.

S3           13         Stores the ASCII decimal code for the Carriage 
			Return character. Valid range is 0-127.

S4           10         Stores the ASCII decimal code for the Line Feed 
			character.  Valid range is 0-127.

S5           8          Stores the ASCII decimal code for the Backspace 
			character.  A value of 128-255 disables the 
			Backspace key's delete function.

S6           2          Sets the number of seconds the modem waits 
			before dialing.  If set to X2, X4, X6, or X7, 
			the modem dials as soon as it detects a dial 
			tone (fast dials).  If there is no dial tone, 
			the modem observes the normal S6 timeout.

S7           60         Sets the number of seconds the modem waits for 
			a carrier.  May be set for much longer duration if, 
			for example, the modem is originating an 
			international connection. 

S8           2          Sets the duration, in seconds, for the pause (,) 
			option in the Dial command and the pause between 
			command re-executions (> and A> commands).

S9           6          Sets the required duration, in tenths of a 
			second, of the remote modem's carrier signal 
			before recognition by the Courier.

S10          7          Sets the duration, in tenths of a second,  that 
			the modem waits after loss of carrier before 
			hanging up.  This guard time allows the modem to 
			distinguish between a line hit, or other 
			disturbance that momentarily breaks the 
			connection, from a true disconnect (hanging up) 
			by the remote modem. 

			While we do not recommend connecting the modem to a 
			line with call waiting, if you have call waiting you 
			may wish to adjust this setting upward to prevent 
			the modem from misinterpreting the signal for a 
			second call as a disconnect by the remote modem.  
			A better alternative is to contact your phone 
			company to find out how to temporarily disable 
			call waiting.

S11          70         Sets the duration and spacing, in milliseconds, 
			of dialed tones. 

S12          50         Sets the duration, in fiftieths of a second, of the 
			guard time for the escape code (+++) sequence.

S13          0          Bit-mapped register.  Select the bit(s) you    
			want on and set S13 to the total of the    
			values in the Value column.  For example,   
			ATS13=20 enables bit 2 (value = 4) and bit 
			4 (value = 16).  Or use ATSr.b=0 (OFF) or 1  
			(ON).  For example, ATS13.0=1 .3=1 turns      
			on bits 0 and 3.   To turn a bit off, set that    
			bit to zero, as in ATS13.3=0.

			Bit    Value   Result
			0      1       Reset when DTR drops
			1      2       Reverse normal Auto Answer operation:  
				       on incoming RING, enter Originate Mode 
				       and look for Answer tone
			2      4       Disable 250 msec. pause before 
				       result code display
			3      8       On DTR signal, Auto Dial the number 
				       stored in NVRAM at position 0 
			4      16      At power on/reset, Auto Dial number 
					stored in NVRAM at position 0 
			5      32      Disable HST (used for testing V.32 
				       terbo in Dual Standard modems)
			6      64      Disable MNP Level 3 (used for testing 
				       Level 2)
			7      128     Custom applications

S14          0          Bit-mapped register.  Select the bit(s) you       
			want on and set S14 to the total of the values in 
			the Value column.
 
			Bit    Value   Result
			0       1       Disconnect on escape code
			1-7     -       Reserved
       
S15          0          Bit-mapped register.  To set the register, see the 
			instructions for S13. 

			Bit    Value   Result
			0      1       Disable the modem's extra high-
				       frequency equalization if it causes 
				       problems on shorter-link calls--modems 
				       only
			1      2       Disable online fallback
			2      4       Disable 450 bps back channel--HST only
			3      8       Reset non-ARQ mode Transmit buffer 
				       from 1.5K bytes to 128* 
			4      16      Disable MNP Level 4; retransmitting 
				       the larger Level 4 data blocks may be 
				       a problem if you expect a great number 
				       of errors during a call
			5      32      Set backspace key to delete
			6      64      Some earlier 2400 bps MNP modems, not 
				       made by U.S. Robotics or Microcom, 
				       were not fully compatible with the MNP 
				       protocol.  If you have difficulty 
				       making a successful 2400 bps MNP 
				       connection with a remote MNP modem, it 
				       may be because of this incompatibility.  
				       Set S15 to 64 and try again to make the 
				       connection. 
			7      128     Custom applications only

		    * The default 1.5K byte non-ARQ buffer allows data 
		      transfer with X-and Ymodem-type file transfer protocols 
		      without using flow control. 

		      The 128-byte option allows remote users with slower 
		      modems to stop data you're transmitting from scrolling 
		      off their screens.  When remote users send your computer 
		      an XOFF (<Ctrl-S>) and you stop transmitting, the data 
		      in transit from your modem's buffer doesn't exceed the 
		      size of their screen. 
    
S16          0          Bit-mapped test register.  To set the register, see 
			the instructions for S13.  For information on 
			testing, see Appendix H.

			Bit    Value   Result
			0      1       Analog Loopback
			1      2       Dial test
			2      4       Test pattern
			3      8       Remote Digital Loopback
			4      16      Reserved
			5      32      Reserved
			6      64      Reserved 

S17          0          Reserved. 
S18          0          Test timer for software-initiated loopback testing 
			(&Tn), disabled when S18 is set to 0.  See Appendix 
			H.  Used to set the duration of testing, in seconds, 
			before the modem automatically times out and 
			terminates the test.

S19          0          Sets the duration, in minutes, for the Inactivity 
			Timer.  The timer activates when there is no data 
			activity on the phone line and at the timeout the 
			modem hangs up.  S19=0 disables the timer.

S20          0          Reserved.

S21          10         Sets, in 10-millisecond units, the length of Breaks 
			sent from the modem to the computer or terminal.  
			Applies to ARQ mode only.

S22          17         Stores the ASCII decimal code for the XON character.

S23          19         Stores the ASCII decimal code for the XOFF character.

S24          150        Sets the duration, in 20-millisecond units, between 
			pulsed DSR signals when the modem is set to &S2 or 
			&S3.  The default is 3 seconds.

S25          5          Sets DTR recognition time in 1/100th of a second 
			units.

S26          1          Sets the duration, in 1/100th of a second units, of 
			the delay between RTS and the modem's CTS response 
			in synchronous mode.  

S27          0          Bit-mapped register.  To set the register, see the 
			instructions for S13.

			Bit     Value   Result
			0       1       Enable ITU-T V.21 modulation at 300 
					bps for overseas calls.  In V.21 
					mode, the modem answers both Bell 
					103 and V.21 calls, but only 
					originates V.21 calls.
			1       2       Enable unencoded (non-trellis-coded) 
					modulation in V.32 mode; this option 
					is part of the ITU-T V.32 
					recommendation, but is rarely used.
			2       4       Disable V.32 modulation; used for 
					testing HST modulation in Dual 
					Standard modems.
			3       8       Disable 2100 Hz answer tone to allow 
					two V.42 modems to connect more 
					quickly.
			4       16      See next page.
			5       32      See next page.
			6       64      Reserved.
			7       128     Unusual software incompatibility.  
					Some software may not accept 7200, 
					12000, 14400, 16800, 19200 and 21600 
					bps result codes.  This setting 
					disables the codes and displays the 
					9600 code instead.  The call's 
					actual rate can be viewed on the 
					ATI6 screen.

					Error control handshaking options:  
					select the total values of bits 4 
					and 5.  

					Bit 4   Bit 5   Result
					0       0       Complete handshaking 
							sequence:  V.42 
							Detection, LAPM 
							error control, 
							MNP
					16      0       Disable MNP
					0       32      Disable V.42 
							Detection and LAPM
					16      32      Disable Detection 
							phase, if you know 
							that the remote modem 
							does LAPM, but not 
							the Detection phase.

S28          8          Sets the duration, in tenths of a second, of the 
			extra 3000/600 Hz answer tones sent during V.32 
			handshaking.  This gives V.32 modems additional 
			time to connect in V.32 mode before timing out.

			If there is difficulty answering older, manually 
			operated V.32 modems, for example, modems that 
			require a button to be pushed in order to dial, 
			try lengthening the duration of the extra tones.

			Setting S28 to zero eliminates the extra tones, 
			resulting in a faster connect time if,    
			for example, the modem is set to use V.21 
			modulation (300 bps) or V.23 modulation  
			(1200 bps).

S29          20         Sets the duration, in tenths of a second, of the 
			answer tones sent during V.21 handshaking.  
			Default = 20 (2 seconds).  This gives V.21 modems 
			additional time to connect in V.21 mode before 
			timing out.

S30-S31      0          Reserved.

S32          9          Sets the function for the voice/data switch.  This 
			is not a bit-mapped register.  Select the value for 
			the desired function, for example, ATS32=6.

			Value   Result
			0       Disabled
			1       Voice/data, Originate mode.  See value 9.
			2       Voice/data, Answer mode
			3       Redial last number
			4       Dial number stored at position 0
			5       Auto Answer on/off toggle
			6       Reset the modem
			7       Initiate Remote Digital Loopback
			8       Busy out phone line toggle
			9       Default if a command string is stored with 
				the &ZC=string command.  When voice/data 
				switch is pushed and &ZC has been enabled, 
				modem executes stored command string.  
				Otherwise acts like value 1, Originate 
				mode

			NOTE:  Only use the voice/data switch when the modem 
			is in Command mode.

S33          0          Setting this register to 1 (S33=1) enables a reduced 
			packet size.

S34          0          Bit-mapped register.  See instructions for S13.

			Bit    Value   Result
			0       1       Disable V.32 bis.  Used for 
					troubleshooting; U.S. Robotics' 
					Technical Support may require that 
					you disable V.32 bis for testing 
					purposes.  
			1       2       Disable the modem's enhanced, 
					proprietary V.32 bis modulation.  
					Used for troubleshooting.
			2       4       Disable the faster retrains that 
					occur during proprietary V.32 terbo 
					modulation.  Used for 
					troubleshooting.
			3       8       Enable V.23.  Required for some 
					British connections.
			4       16      Change MR LED to DSR.
			5       32      Enable MI/MIC; see Appendix G.
			6       64      Disable the remote access busy 
					message.
			7       128     Disable V.32 terbo.

S35-S37      0          Reserved.

S38          0          Sets the duration, in seconds, before a forced 
			hang-up and clearing of the Transmit buffer, when 
			DTR drops during an ARQ call.  This is provided to 
			allow time for a remote modem to acknowledge receipt 
			of all transmitted data.  Default = 0:  the modem 
			immediately hangs up when DTR drops.  If the modem 
			receives the ATH command, it ignores S38 and 
			immediately hangs up.
       
S39-S40      0          Reserved.

S41          0          Sets the number of allowable remote access login 
			attempts, thus enabling or disabling remote access.  
			The default setting of zero allows no remote login 
			attempts, thus disabling remote access.  A value of 
			1 or greater enables remote access.  If the number 
			of unsuccessful login attempts exceeds the limit set 
			by this register, the modem returns online and any 
			further login attempts during the remainder of that 
			connection are refused.

S42          126        Stores the ASCII decimal code for the remote access 
			escape character.  The default character is a 
			tilde (~).

S43          200        Sets the duration, in fiftieths of a second, of the 
			guard time for the remote access (~~~~) sequence.

S44          15         Sets the duration, in seconds, of the delay between 
			when the modem senses loss of carrier and when it 
			attempts to re-establish a leased-line connection.  

S45-S50      0          Reserved.


S51          0          Bit-mapped register.  See instructions for S13.

			Bit     Value   Result
			0       1       Disable MNP/V.42 for
					V.22 (1200 bps)
			1       2       Disable MNP/V.42 for
					V.22 bis (2400 bps)
			2       4       Disable MNP/V.42 for
					V.32/V.32 bis/V.32 terbo 
					(9600/14,400/19,200/
					21,600 bps).
			3-6     -       Reserved
			7       128     Custom Applications.  Handset 
					Exclusion Delay.  If the telephone 
					and modem share the same line, and 
					DTR is raised, the modem takes 
					control of the phone line and 
					disconnects the voice call.  The 
					modem stays on hook for the duration 
					specified in S6 before it becomes a 
					data call.

					Since there is no way to detect if 
					the telephone is in use, the S6 delay 
					occurs even if the telephone is not 
					in use.

					The phone is re-enabled once the modem 
					returns on hook.

S52           0          Reserved.

S53          0          Bit-mapped register.  Select the Dial Security 
			features you want enabled by setting S53 to the 
			total of the values in the Value column in the 
			table below.  For example, S53=3, enables Dial 
			Security with prompting.  S53=5 enables Dial 
			Security, and local-access password protection.  
			Or use ATSr.b=0 (OFF) or 1 (ON).  For example, 
			ATS53.0=1 .2=1 turns on bits 0 and 2.   To turn a 
			bit off, set that bit to zero, as in ATS53.2=0.

			Bit     Value   Result
			0       1       Dial security enabled
			1       2       Prompting enabled
			2       4       Local-access password
					protection enabled

			NOTE:  In addition, enabling local access password 
			protection disables the &Zn=s command which stores 
			up to ten phone numbers because stored phone numbers 
			occupy the same space in NVRAM as the dialback 
			numbers for Dial Security accounts.

S54          0          Symbol rate bit-mapped register used primarily by 
			U.S.Robotics Technical Support for debugging 
			purposes.

			Bit 6 (ATS54.6=1) disables Call Indicate (CI).

			Bit 7 (ATS54.7=1) disablesV.8.

S55          0          Trellis code bit-mapped register used primarily 
			by U.S.Robotics Technical Support for debugging 
			purposes.

S56          0          Bit-mapped register primarily used by U.S.Robotics 
			Technical Support for debugging purposes.  

			Bit 6 (ATS56.6=1) disables V.34 modulation.

			Bit 7 (ATS56.7=1) disables V.FC modulation.

S57          0          Reserved for German operations.

Appendix C--Alphabetical Command Summary


Additional command summaries are in Chapter 4, on the bottom panel of the 
modem, and in the Quick-Reference Card.

*****************
COMMAND SET USAGE

Follow these guidelines:
1. Your software must be loaded and if you are using a computer, it must be 
   in Terminal mode.  

   Some communications programs put the computer in terminal mode 
   automatically when they are loaded.  Others require you to display a 
   communications terminal screen, press a Function key, or perform some 
   other operation.  Refer to your communications software documentation 
   for instructions.

   In Terminal mode the computer acts as if it were a standard terminal 
   such as a teletypewriter, rather than a data processor.  Keyboard 
   entries go directly to the modem, whether the entry is a modem command 
   or data to be transmitted over the phone lines.  Received data is 
   output directly to the screen. 

2. Type commands in either upper or lower case, not a combination (AT or 
   at--not At).

3. All commands except A/, A> and +++ are preceded by the AT (attention) 
   prefix and are executed with the Enter/Carriage Return key (<Enter>).

4. Command length = 60 characters maximum.  The modem doesn't count the 
   AT prefix, Carriage Return character, or spaces.  It counts (but 
   doesn't act on) punctuation such as hyphens and parentheses.

5. A missing numeric parameter is assumed to be zero, as in the command 
   to hang up:  ATH <Enter> is the equivalent of ATH0 <Enter>.

   Example (spaces are not required, but are added here for readability):

	    AT &K3 X2 DT 071 312 1234 <Enter>

   AT      Attention; a command follows.
   &K3     Disable MNP5 data compression; use only V.42 bis compression.
   X2      Use the X2 result code subset.
   DT      Dial the following number using tone dialing.
   <Enter> Execute the commands.

   NOTE:  The defaults listed are based on the modem's shipping 
   configuration:  load from nonvolatile random access memory (NVRAM), 
   DIP switch 10 OFF, which is the same as the &F1 configuration template.  
   For a complete listing of default configuration templates, see Appendix B.

*****************
Basic Command Set

+++     Escape code operations.  Once the modem is online to another system, 
	the only command it recognizes is an escape code of three typed 
	pluses, which forces the modem back to Command mode.  Do the 
	following when issuing the command:  

	*  Wait one second after sending the last item of data
	*  Type: +++
	*  Wait one second before typing any data

	Do not type the AT prefix or a Carriage Return.  The guard time of 
	one second before and after the code prevents the modem from 
	misinterpreting the occurrence of +++ in the transmitted data 
	stream.  

	If necessary, the character used in the escape code or the 
	duration of the guard time can be changed by resetting Register 
	S2 or S12.  See the S-Register Summary in Appendix B.

	In response to +++ the modem returns to Command mode.  However, it 
	keeps the line open or hangs up, depending on the setting of DIP 
	switch 9: 

	DIP Switch 9    Response to +++
	OFF             Modem goes on hook (hangs up), sends NO CARRIER 
			result code (factory setting)
	ON              Modem maintains connection (Online-Command mode), 
			sends OK result code 

	The factory setting (OFF) forces an automatic disconnect when you 
	issue +++.   An advantage of this is that you are not likely to 
	inadvertently run up an all-night phone bill.  

	Set DIP switch 9 ON if you want the modem to respond to +++ by 
	entering Online-Command mode, enabling it to execute commands and 
	return online.  (See the O command later in this appendix.)  

>       If you know the modem you are calling is frequently busy, include 
	the Repeat command in the Dial string, as follows:

	       AT > DT 1234567 <Enter>  
			or
	       AT DT 1234567 > <Enter>

	The modem enters Repeat mode, dials the number, waits 60 seconds 
	for a carrier (default), and hangs up.  Then after a two-second 
	pause, it redials.  

	The cycle continues until the modems connect or the modem reaches 
	a maximum of 10 attempts.

A       Force Answer mode when the modem hasn't received an incoming call.

A/      Re-execute the last issued command.  A/ doesn't take the AT prefix 
	or a Carriage Return, and can be used to redial.

A>      This command combines the features of both the A/ and > commands.  
	The modem enters Repeat mode and redials the Dial string in the 
	command buffer.  Like the A/ command, A> does not take the AT 
	prefix or a Carriage Return.

AT      Attention command prefix.  Use AT alone to test for the OK result 
	code.  AT must prefix all commands except A/, A> and +++.

Any     Terminate the current dialing operation resulting from an
key     issued Dial command; terminate Repeat mode (> or A>).

Bn      Handshake options for international calls above 1200 bps.
	B0  ITU-T (formerly CCITT) answer sequence.  Default.  This is 
	    required to answer all V.32-type calls as well as calls from 
	    overseas.
	B1  Bell answer tone.  This setting selects HST modulation in 
	    Dual Standard modems; but should only be used if the modem is 
	    not required to answer V.32-type calls.  
    
	    NOTE:  This setting is required for HST cellular calls.

Cn      Transmitter enabled/disabled.
	C0  Transmitter disabled; receive-only condition.
	C1  Transmitter enabled (Default).

Dn      Dial the specified phone number; also execute Dial options.

	The maximum number of characters allowed is 36, including the AT 
	prefix, punctuation and spaces.  The Carriage Return (Enter key) 
	isn't counted as a character.

	NOTE:  With the exception of the Dial options, the modem ignores 
	any commands issued after D in the same command string.  

D       Dial the number that follows and enter Originate mode.  Optional 
	parameters:
	P     Pulse dial (Default).
	T     Tone dial.
	,     (Comma) Pause for 2 seconds before continuing to dial.
	;     Return to Command mode after dialing.  
	"     Dial the letters that follow (in an alphabetical phone number).  
	!     Transfer a call (flash the switch-hook).  This command applies 
	      to modems in installations where other modems share the phone 
	      line.  The modem flashes the switch-hook (goes off hook 0.5 
	      seconds, on hook for 0.5 seconds and off hook again) to dial 
	      the specified extension.
	W     This command is useful in situations where you must wait for a 
	      second dial tone before continuing dialing.
	@     Wait for an answer (with X3 or higher).  The @ command can be 
	      used in the Dial string to tell the modem to detect at least 
	      one ring, wait for five seconds of silence at the other end of 
	      the call, and then continue to execute the Dial string.
	/     A slash (/) causes a pause of only 125 milliseconds.
	R     Reverse frequencies.  This command allows calls to an 
	      originate-only modem.  It reverses the modem's originate/answer 
	      frequencies, forcing the Courier to dial out at the answer 
	      frequency.

DL      Dial the last-dialed number.  The modem stores each Dial command 
	until it receives the next Dial command.  Use DL instead of A/, 
	described on the next page, if you wish to send the modem non-Dial 
	commands before dialing again.

DSn     Dial the number stored in nonvolatile random access memory at 
	position n, where n = 0-9. 

En      Command mode local echo.  Enables/disables the display of your 
	typed commands.  If double characters appear on the screen, both the 
	modem's local echo and your software's local echo are on.  

	The Courier is shipped with DIP switch 4 OFF, enabling local echo.  
	The En command controls the local echo for a current session, 
	independently of the switch setting. 

	E0  Command mode echo OFF.  The modem does not display keyboard 
	    commands.
	E1  Command mode echo ON.

Fn      Online local echo.  This command causes the modem to display a copy 
	of the data it is transmitting to another system.
	F0  Online echo ON.  Sometimes called half duplex.  As the modem 
	    transmits data to a remote system, it also sends a copy of the 
	    data to the screen.
	F1  Online echo OFF.  Sometimes called full duplex.  Default.

Hn      On/off hook control.
	H0  Hang up (go on hook).
	H1  Go off hook.

In      Inquiry
	I0  Display product code
	I1  Display results from ROM checksum
	I2  Display results from RAM test
	I3  Display the duration of the last call
	I4  Display current modem settings
	I5  Display NVRAM settings
	I6  Display Dial diagnostics summary of the last call
	I7  Display product configuration information
	I8  Reserved
	I9  Reserved
	I10 Display dial security account status information
	I11 Display a high speed connection report

Kn      Modem clock operation:  Call-duration or Real-time mode.  Displayed 
	with ATI3 and ATI6 commands.
	K0  Display current call-duration if online.  Display last 
	    call-duration if offline.  Default.
	K1  Return actual time at ATI3.  Clock is set using ATI3=HH:MM:SS K1.

Ln      Speaker volume control (internal modems only)
	L0  Low
	L1  Low
	L2  Medium (default)
	L3  High

	NOTE:  External modems will return an OK message to this command, 
	but the volume will not change.  The volume button must be used to 
	alter volume.

Mn      Speaker (audio monitor).
	M0  The speaker is always OFF.
	M1  The speaker is ON until carrier is established (Default).
	M2  The speaker is always ON, including during data transfer.
	M3  The speaker is ON after the last digit is dialed and remains 
	    ON until carrier is established.

On      If DIP switch 9 is ON (on detection of the escape code the modem 
	maintains the connection), you can issue commands and then toggle 
	the modem back online with the On command.

	There are two ways to return online.

	ATO0 Return online (normal).  
	ATO1 Return online and retrain.  Use to have the modem 
	re-synchronize if there were errors in a non-ARQ data transfer.

Qn      Enable/suppress the display of result codes.  The Courier is 
	shipped with DIP switch 3 ON, to display result codes.  Use the Qn 
	command to control the display for a current session, independently 
	of the switch setting. 

	Q0  Result codes displayed.
	Q1  Result codes suppressed (quiet).
	Q2  Result codes suppressed in Answer mode.

Sr=n    Set S-Register value:  r is any S-Register; n must be a decimal 
	number between 0 and 255.

Sr.b=n  Alternative command for setting bit-mapped registers:  r is the 
	bit-mapped register; .b is the bit; n is 0 (off) or 1 (on).

Sr?     Query contents of register r.

Vn      Return result codes in words or numbers (Verbal/Numeric mode).  
	V0  Numeric mode.
	V1  Verbal mode.

Xn      Result code set options.  Use the following table (Default = X7, 
	all codes except 12/VOICE).  For result codes in synchronous 
	operations, see Appendix F.
 
				    Setting        
Result Codes    X0      X1      X2      X3      X4      X5      X6      X7
0/OK            ·       ·       ·       ·       ·       ·       ·       ·
1/CONNECT       ·       ·       ·       ·       ·       ·       ·       ·
2/RING          ·       ·       ·       ·       ·       ·       ·       ·
3/NO CARRIER    ·       ·       ·       ·       ·       ·       ·       ·
4/ERROR         ·       ·       ·       ·       ·       ·       ·       ·
5/CONNECT 1200          ·       ·       ·       ·       ·       ·       ·
6/NO DIAL TONE                  ·               ·               ·       ·
7/BUSY                          ·       ·       ·       ·       ·
8/NO ANSWER                             ·       ·       ·       ·       ·
9/RESERVED
10/CONNECT 2400         ·       ·       ·       ·       ·       ·       ·
11/RINGING                                              ·       ·       ·
12/VOICE                                                ·       ·       
13/CONNECT 9600         ·       ·       ·       ·       ·       ·       ·
18/CONNECT 4800         ·       ·       ·       ·       ·       ·       ·
20/CONNECT 7200         ·       ·       ·       ·       ·       ·       ·
21/CONNECT 12000        ·       ·       ·       ·       ·       ·       ·
25/CONNECT 14400        ·       ·       ·       ·       ·       ·       ·
47/CONNECT 16800        ·       ·       ·       ·       ·       ·       ·
85/CONNECT 19200        ·       ·       ·       ·       ·       ·       ·
91/CONNECT 21600        ·       ·       ·       ·       ·       ·       ·
99/CONNECT 24000        ·       ·       ·       ·       ·       ·       ·
103/CONNECT 26400       ·       ·       ·       ·       ·       ·       ·
107/CONNECT 28800       ·       ·       ·       ·       ·       ·       ·
Functions
Adaptive Dialing                ·       ·       ·       ·       ·       ·
Wait for 2nd Dial Tone (W)              ·       ·       ·       ·       ·
Wait for Answer (@)                     ·       ·       ·       ·       ·
Fast Dial                       ·               ·               ·       ·


Z       Software reset to NVRAM settings when DIP switch 10 is OFF (factory 
	setting).  If DIP switch 10 is OFF, the modem resets to the &F0 
	configuration template, with no flow control.

*************************
Ampersand (&) Command Set
&An     Enable/disable additional result code subsets.  See the Xn command.
	&A0     ARQ result codes are disabled.
	&A1     ARQ result codes enabled.
	&A2     Additional VFC, HST, or V32 modulation indicator.
	&A3     Additional error control indicator (LAPM, HST, MNP, SYNC, 
		or NONE) and data compression type (V42BIS or MNP5).  
		Default.

&Bn     Serial port rate variable or fixed.
	&B0 Variable rates.
	&B1 Fixed rate.  Default.  The modem always communicates with the 
	    computer at the rate at which you have set the terminal or 
	    software, regardless of the connection rate.  
    
	    This setting is not affected by the &N setting.  However, the 
	    serial port rate must be equal to or higher than the &Nn rate.

&B2 Fixed for ARQ calls/Variable for non-ARQ calls.  Answer mode 
	    only.  When the modem goes off hook and connects in ARQ mode, 
	    it shifts its serial port rate up to a user-specified rate, 
	    for example, 38.4K bps.  If the connection is not under error 
	    control, the modem behaves as if it were set to &B0 and 
	    switches its serial port rate to match the connection rate of 
	    each call.

&Cn     Carrier Detect operations.  At power-on and reset, the modem 
	operates according to the setting of DIP switch 6.  This command 
	is not stored in nonvolatile memory as a power-on/reset default.

	&C0 CD override, CD always ON.
	&C1 Normal CD operations.  The Courier sends a CD signal when 
	    it connects with another modem and drops the CD when it 
	    disconnects.

&Dn     Data Terminal Ready (DTR) operations.  At power-on and reset, the 
	modem operates according to the setting of DIP switch 1.  This 
	command is not stored in nonvolatile memory as a power-on/reset 
	default.

	&D0 DTR override.  The modem operates as though the DTR is always ON.

	&D1 Advance usage:  If issued before connecting with another modem, 
	    the modem can enter online command mode during a call by 
	    toggling DTR.  &D1 functions similarly to the escape code 
	    (+++), except that this setting is independent of DIP switch 9.

	    If DIP switch 1 is ON (DTR override) when you issue the &D1 
	    command, the DTR override is automatically turned off.  
	    However, if you change the setting of DIP switch 1 after 
	    issuing &D1, the DIP switch setting tales precedence.

	    Return online with the On command, or hang up with the Hn 
	    command.

	&D2 Normal DTR operations.  The terminal or computer must send a 
	    DTR signal for the modem to accept commands.  Dropping DTR 
	    terminates a call.

&Fn     The modem is shipped with four configurations (templates), 
	&F0-&F3, stored in permanent nonprogrammable memory (ROM).  
	Appendix B includes configuration listings for each template.  
	Any one of the templates may be loaded into current memory 
	(AT &Fn) or written to nonvolatile memory and reset default 
	(AT &Fn &W).  Note, however, that &F0 is always loaded into 
	memory if DIP switch 10 is ON. 

	&F0 Load No Flow Control template settings
	&F1 Load Hardware Flow Control template settings (Default)
	&F2 Load Software Flow Control template settings
	&F3 Load HST Cellular template settings

&Gn     This setting applies only to overseas calls at 2400 or 1200 bps.  
	British phone switching systems require the modem to send an 1800 
	Hz guard tone after it sends an answer tone.  Some other European 
	phone networks require a 550 Hz guard tone.  Guard tones are not 
	used in the United States or Canada.

	&G0 No guard tone.  This is used in the U.S. and in Canada (Default).
	&G1 This sets a 550 Hz guard tone, and is used in some European 
	    countries.
	&G2 This sets an 1800 Hz guard tone, and is used in the U.K. and 
	    some Commonwealth countries.  &G2 requires the B0 setting.

&Hn     Transmit data flow control is for data transmitted to the modem 
	by its attached computer or terminal.  The modem monitors its 
	buffer as data comes from the computer or modem.  If the buffer 
	approaches 90% capacity, the modem signals the computer or terminal 
	to stop transmitting.  When the modem has sent enough data over 
	the link to half empty the buffer, it signals the computer or 
	terminal to resume transmitting.

&H0     Transmit Data flow control disabled.
	&H1 Hardware flow control.  Default.  Requires that your computer 
	    or terminal and software support Clear to Send (CTS) at the 
	    RS-232 interface.
	&H2 Software flow control.  Requires that your software support 
	    XON/XOFF signaling.
	&H3 Use both hardware and software flow control.  If you are unsure 
	    about what your equipment supports, select this option. 

&In     Received data software flow control.

	&I0 Disables XON/XOFF flow control of received data. Default.

	&I1 The Courier acts on your typed XON/XOFF commands, Ctrl-S or 
	    Ctrl-Q, and passes them to the remote computer. 

	&I2 The Courier acts on your XON/XOFF commands, but removes them 
	    from the data stream instead of passing them to the remote 
	    computer.  This is the recommended setting for ARQ mode.

	&I3 Hewlett Packard--Host mode.  Applies only to modems attached to 
	    an HP mainframe that uses the ENQ/ACK protocol.  Use in ARQ 
	    nmode only.  See Appendix G.

	&I4 Hewlett Packard--Terminal mode.  Applies only to modems 
	    attached to terminals in an HP system that uses the ENQ/ACK 
	    protocol.  Use in ARQ mode only.  See Appendix G.

	&I5 This setting is designed to enable flow control on the phone 
	    link when the connection is not under error control.  For this 
	    to work for you, the remote modem must have &I5 capability.

&Kn     Enable/disable data compression.
	&K0 Data compression disabled.
	&K1 Auto enable/disable.  Default.  The modem enables compression 
	    if the serial port rate is fixed, &B1, and disables compression 
	    if the serial port rate follows the connection rate, &B0, 
	    because compression offers no throughput advantage when the 
	    serial port and connection rates are equal.  Compression may 
	    even degrade throughput. 
	&K2 Data compression enabled.  Use this setting to keep the modem 
	    from disabling compression. 
	&K3 Selective data compression.  The modem negotiates only for 
	    V.42 bis compression, and disables MNP Level 5 (MNP5) 
	    compression.  Use this setting to transfer 8-bit binary 
	    files, .ZIP files, and other files that are already compressed.

&Ln     Normal/Leased phone line.
	&L0 Normal phone line.  Default.
	&L1 Leased line; enables modem to reconnect if disconnected.
	&L2 Cellular operations; with B1, enables HST Cellular mode.

&Mn     Enable ARQ (error control) or synchronous protocols.  Both your 
	modem and the remote modem must use the same protocol.
	&M0 Normal mode, no error control.  Due to the nature of phone 
	    line channels, this is never recommended for calls above 2400 
	    bps.  
	&M1 This setting is exclusive of the modems' error control and is 
	    used only for online synchronous mode without V.25 bis.  See 
	    Appendix F for more information.
	&M2 Reserved.
	&M3 Reserved.
	&M4 Normal/ARQ mode.  Default.  If an ARQ connection isn't made, 
	    the modem operates in Normal mode, as though it were set to &M0.
	&M5 The modem enters ARQ asynchronous mode.  The modem hangs up if 
	    an ARQ connection cannot be made.  
	&M6 The modem enters V.25 bis synchronous mode, using a character-
	    oriented link protocol similar to BISYNC.  See Appendix F for 
	    more information.
	&M7 The modem enters V.25 bis synchronous mode, using the HDLC link 
	    protocol.

&Nn     Connection rate variable or fixed.
	&N0  Variable rates.  Default.  The Courier negotiates with the 
	     remote modem for the highest possible connection rate, 
	     depending on the capabilities of the remote modem.  This is 
	     the recommended setting.  
	&N1- Fixed rate.  The modem only connects if the remote modem is
	&N14 operating at the same rate.  If not, the modem hangs up.  If 
	     you wish, you can filter out calls at other than a specific 
	     rate, for security or other reasons, by fixing the connection 
	     rate.

	     The connection rate must always be lower than, or equal to, 
	     the serial port rate, never higher.  
       
	The options are as follows.
	&N1   300 bps         &N9   16.8K bps (HST, terbo,
	&N2   1200 bps                 V.FC, and V.34 only)
	&N3   2400 bps        &N10  19.2K bps (terbo, V.FC, 
	&N4   4800 bps                 and V.34 only)
	&N5   7200 bps        &N11  21.6K bps (terbo, V.FC,
	&N6   9600 bps                 and V.34 only)
	&N7   12K bps         &N12  24K bps (V.FC and V.34 only)
	&N8   14.4K bps       &N13  26.4K bps (V.FC and V.34 only)
			      &N14  28.8K bps (V.FC and V.34 only)

&Pn     This command sets the ratio of the off-hook/on-hook (make/break) 
	interval for pulse dialing.  The default sets the modem for use 
	in North America.  The ratio must be changed if the modem is used 
	in the United Kingdom and some Commonwealth countries.
	&P0 Make/break ratio, U.S./Canada:  39%/61%.  Default.  
	&P1 Make/break ratio, United Kingdom, some Commonwealth 
	    countries:  33%/67%.

&Rn     Received data hardware (RTS) flow control
	&R0 Delay Clear to Send Response after Request to Send signal 
	    (RTS/CTS delay).  
	&R1 The modem ignores RTS.  This setting is required if your 
	    computer or terminal or software does not support RTS.
	&R2 Hardware flow control of received data enabled.  Default.  
	    The modem sends data to the computer or terminal only on 
	    receipt of the RTS signal.

&Sn     The modem sends the computer or terminal a Data Set Ready (DSR) 
	signal via the RS-232 interface.  (Data Set is industry jargon for 
	modem.)  
	&S0 DSR is always ON (override).  Default.
	&S1 In Originate mode, the modem sends the DSR after it dials, 
	    when it detects the remote modem's answer tone.  In Answer 
	    mode, the modem sends the DSR after it sends an answer tone.
	&S2 This option is for specialized equipment such as automatic 
	    callback units.  On loss of carrier, the modem sends a pulsed 
	    DSR signal with Clear to Send (CTS) following Carrier Detect (CD).
	&S3 This is the same as &S2, but without the CTS following CD.
	&S4 The modem sends the computer a DSR signal at the same time as 
	    it sends the Carrier Detect (CD).
	&S5 CTS follows Carrier Detect with DSR normal

&Tn     Modem testing
	&T0 End test
	&T1 Initiate Analog Loopback (AL) testing
	&T2 Reserved
	&T3 Initiate Local Digital Loopback (LDL) testing
	&T4 Grant Remote Digital Loopback (RDL)
	&T5 Deny RDL
	&T6 Initiate RDL testing
	&T7 Initiate RDL with self test and error detection
	&T8 Initiate AL with self test and error detection

&W      Write the curent settings to NVRAM.

&Xn     Synchronous transmit clock timing signals setting.  Determines 
	whether the modem or DTE will generate the timing signals.

	&X0 The Courier is the source of the Transmit clock timing 
	    signals and sends them to your DTE over the RS-232 interface.  
	    The DTE rate will follow the connection rates.  Default.

	&X1 The DTE is the source of the Transmit clock timing signals 
	    and sends them to the Courier over the RS-232 interface.  This 
	    setting is used typically in leased line multiplexed operations.
	    (Multiplexors divide the phone channel so that the channel 
	    carries several calls at the same time.)  
    
	    The DTE ignores the Courier's clock timing signals and 
	    negotiates the DTE and connection rates.

	&X2 The Courier's Receiver clock is the source of the timing 
	    signals.  The signals are looped to the Transmit clock and 
	    sent to your DTE over the RS-232 interface.  This setting is 
	    only used in those systems that require synchronization of 
	    data flowing in both directions.

&Yn     Break handling.  This command allows you to send a break to abort 
	data transfer without disconnecting from the phone link.
	&Y0 Destructive, don't send Break.
	&Y1 Destructive, expedited (Default).
	&Y2 Nondestructive, expedited.
	&Y3 Nondestructive, unexpedited; modem sends Break in sequence 
	    with data received from computer or terminal.

&ZC?    Display the stored command string.

&ZC=s   Write the following command string s to NVRAM.  The command string 
	may be up to 40 characters long; spaces are not counted.  This 
	command can be used so that you can call another modem without 
	loading your communications software.

	After storing a command, you can program the voice/data switch 
	to execute the stored command string when pressed.  The following 
	example assigns a command string that displays the link diagnostics 
	screen when you press the voice/data switch.  

	       AT&ZC=I6 <Enter>

	The function of the voice/data switch is determined by the setting 
	of Register S32, as described in Appendix G.  Set the voice/data 
	switch function to execute stored command string by setting 
	Register S32 to 9 with the following command:

	      ATS32=9 <Enter>

	Note that you can reset the voice/data switch at any time to one of 
	the other available functions.  Additionally, you can overwrite the 
	stored command string with a new one at any time.

	Once you've stored your command string and set Register S32, all 
	you need to do is press the voice/data switch whenever you want 
	the command string executed.

&Zn=s   This command stores up to ten numbers, where n is the position 
	0-9 in nonvolatile memory, and s is the phone number string.  
	The number-string may be up to 36 characters long, including 
	any Dial command options.  

	      AT &Z2=555-6789 <Enter>

	Do not include modem settings in the &Zn string.  If the call 
	requires a special setting, insert it in the command string 
	before the DSn command.  In the following example, &M0 (no 
	error control) is inserted before the Dial command:

	      AT&M0 DS2 <Enter>

	NOTE:  The &Zn=s command functions differently when Dial Security 
	is enabled.  See Appendix D for more information.

&Zn?    Display the phone number stored in NVRAM at position n (n = 0-9).

*******************
Percent Command Set
%An     Create and configure security accounts.  See Appendix D.

%Bn     Remotely configure the Courier's serial port rate.  See Appendix D.
	%B0  110 bps            %B6   9600 bps
	%B1  300 bps            %B7   19,200 bps
	%B2  600 bps            %B8   38,400 bps
	%B3  1200 bps           %B9   57,600 bps
	%B4  2400 bps           %B10  115,200 bps
	%B5  4800 bps

%Cn     Remote configuration control.  See Appendix D.
	%C0  Defer configuration.   This is the default.  Configuration 
	     changes are deferred until the call is ended; they take effect 
	     for ensuing connections.  You do not need to enter this 
	     command; it is the default unless you enter %C1 or %C2.
	%C1  Restore configuration.  Use this command to cancel any 
	     configuration changes made during remote access, and restore 
	     the original configuration.  However, commands that have been 
	     written to NVRAM (with &W) will not be restored to their 
	     previous settings.  Additionally, if you have forced immediate 
	     configuration changes (with %C2), those changes cannot be 
	     reversed with %C1.
	%C2  Execute configuration.  Use this command to force configuration 
	     changes to take effect immediately, during the current 
	     connection.  We recommend against forcing immediate 
	     configuration changes unless absolutely necessary, as this 
	     can result in an unreliable connection or even a loss of 
	     connection.

%E=n    Make security system edits.  See Appendix D.
	%E=1  Erase local access password. 
	%E=2  Erase autopass password.
	%E=3  Erase passwords in accounts 0–9.
	%E=4  Erase phone numbers in accounts 0-9.
	%E=5  Disable Account, Dialback, and New Number fields in 
	      accounts 0-9 disabled.

%Fn     Remotely configure data format.  See Appendix D.
	%F0  No parity, 8 data bits.
	%F1  Mark parity, 7 data bits.
	%F2  Odd parity, 7 data bits.
	%F3  Even parity, 7 data bits.

%L=     Assign an account password as the local access password.  See 
	Appendix D.

%N      Works in conjunction with &Xn in synchronous mode.  If the modem 
	is set so that it is the source of the Transmit clock timing 
	signals (&X0--default), the %Nn commands set the computer or 
	terminal-to-modem V.25 bis clock speed.  If the modem is set to 
	&X1, the computer is the source of the Transmit clock signals.  

	If %Nn is set to 0 or 1, you will receive an error message, since 
	they are not valid values.  The %Nn rates are as follows:

	%N0   Reserved             %N6   9600 bps (default)
	%N1   Reserved             %N7   12.K bps
	%N2   1200 bps             %N8   14.4K bps
	%N3   2400 bps             %N9   16.8K bps
	%N4   4800 bps             %N10  19.2K bps 
	%N5   7200 bps

%Pn=    Disables password security (n=0 or 1) when no character follows 
	the equal sign.  See Appendix D.

%Pn=s   Specify the following password string (s) for viewing privileges 
	only (n = 0) or view and configuration privileges (n= 1).  See 
	Appendix D.

%Pn?    Display password n.  See Appendix D.

%S=n    Obtain access to security accounts without disabling security.  
	See Appendix D.

%T      Enables the modem, when off hook, to detect the tone frequencies 
	of dialing modems.  %T is meant primarily for use with network 
	applications, but may also be integrated into certain software 
	programs.  For example, %T could be used in a security program 
	to identify incoming tone security codes.
	
	To enable %T, type ATH1 <Enter> to force the modem off hook.  
	Then type AT%T <Enter>.  

	To return the modem to Command mode, press any key or drop the 
	computer's or terminal's DTR signal.  The modem responds OK.

%V=PWn  Assign the password in account n in your Courier modem’s security 
	as your autopass password.  See Appendix D.

Appendix D--Dial Security and Remote Access Operations

_____________________________________________________________________
DIAL SECURITY OPERATIONS              

Dial Security is designed to protect networks and data centers from 
unauthorized access.  The kind of security provided by the Courier modem 
is different from other kinds of dial security where software is used by 
the computer to control user access.  The Courier’s Dial Security is set 
up in the modem’s firmware, so access is controlled from modem to modem.

Setting up this kind of security requires action at both the host and 
remote modem sites.  This appendix contains instructions for both 
operations.

WARNINGS:  

If you want to set up Security on your Courier modem, you must complete 
the steps below in the order listed:

1. Set up your own security account: 
   *  Set up your local access password
   *  Enable local access password protection

2. Set up remote user accounts.

3. Enable Dial Security.

You must set up your local access security information before enabling 
Dial Security and allowing remote calls, as outlined under Set Up Your 
Security Account in what follows.  

Be sure to remember your local access password; if you enable security 
and forget your local access password, you risk being locked out of 
your system.

********
Overview
The Courier’s Dial Security allows you to configure up to 10 Security 
accounts.  Each security account is stored in nonvolatile memory (NVRAM) 
and may be set up in one of three ways:

* Automatic password access
* Prompted password access
* Password with Dialback protection


Autopass
Autopass is the term we use for the basic implementation of Dial Security 
in the Courier modem.  It is in effect whenever Dial Security is enabled.

To use autopass alone, the following requirements must be met:
* Both host and remote modems must be U.S. Robotics modems with 
  Dial Security enabled.
* The connection must be under V.42 error control (both modems must be 
  set to &M4 or &M5).

When the remote modem is set for Dial Security, it automatically 
includes an autopass password (configured by the remote user to be 
compatible with the host modem’s security) in its V.42 error control 
request.  The host modem checks all the enabled passwords in its 
security accounts for a match.

If the remote user has set up the modem with an invalid password, the host 
modem returns an INVALID PASSWORD message and hangs up.

If the remote user failed to enable Dial Security on the remote Courier, 
the host Courier will not accept the call unless prompting (below) is 
enabled on the host modem.


Prompting
While the use of autopass (above) is restricted to U.S. Robotics Dial 
Security modems, prompting allows secured connections with any remote 
modem whose user has been assigned an allowed password.  When prompting 
is enabled, and the host modem doesn’t receive an autopass password, it 
prompts the remote user for a password.  The host modem checks the 
received password against each of its active Security accounts. If the 
password is valid, a secure connection is completed.

If the password is invalid, the host modem prompts twice more before 
disconnecting.  

If there are no password attempts at the remote end, the host modem 
times out after 60 seconds and disconnects.

NOTE:  There is no prompting capability in synchronous mode.

Prompting is more flexible than autopass because it:
* doesn't require a remote modem to have U.S. Robotics Dial Security.
* doesn't require a V.42 connection, so remote modems without V.42 
  error control capabilities can connect.


Optional Dialback
Dialback offers an additional layer of security.  When the host modem 
receives a valid password that matches an account and Dialback is enabled, 
the host first disconnects.  The remote user receives a NO CARRIER message.  
Then the host modem dials back the remote modem.

Typically, the Dialback number is stored in the Security account’s phone 
number field.  However, if the security account has been set up to allow 
a new number, the host prompts the remote user for the new number before 
hanging up, and then dials back.

In order to use dialback, Dial security and prompting must be enabled.


****************************************
WHAT THE HOST MODEM OPERATOR NEEDS TO DO

Complete the steps below in the order listed:
1. Set up your own Security account.
2. Set up Security accounts for your remote users.
3. Enable Dial Security.
4. Maintain Security accounts.

****************************
Set Up Your Security Account
Security accounts are set up via an AT command line structure, rather 
than a screen format.  

1. Set up your Security account using one of 10 accounts (numbered 0-9).  
   Each account has five possible fields, as shown in the following table.  


Password        Account   Dialback        Allow New        Dialback
Enabled         Enabled   Enabled         Number           Number
8 chars. max.   YES/NO    YES/NO          YES/NO           Up to 37                                           
ASCII 37-127                                               characters 
case sensitive*                                            (0-9)

BILL              Y         Y                N            1-419-555-5555

*  If "BILL" is the password, "Bill" is an invalid entry.


Use the %An= command and format (below) to set up accounts, where n is the 
account number, 0-9.  The fields in the above table are entered after the 
equal sign, each separated by a comma, as in the following example for 
account 0 with the password BILL.

WARNING:  Do not insert spaces between commas or between fields and commas.  
Spaces will invalidate the command.

           AT%A0=BILL,Y,Y,N,1-419-555-5555 <Enter>

This example instructs the modem to store the configuration for account 0:  
password (BILL), account enabled (Y), dialback enabled (Y), allow a new 
number (N), and the dialback phone number.  

NOTE:  The %An= command is automatically written to NVRAM and does not 
require an &W.

Some accounts may have fewer security options.  The following example sets 
the password (Judy) and enables account 1 without any dialback options.

          AT%A1=Judy,Y,,, <Enter>

Each security function can be configured or modified independently.  If a 
field is to remain as is, just insert a comma, as shown in the following 
command.  It allows the remote user to supply a new Dialback number 
different from the one stored in the original account record.

         AT%A0=,,,Y, <Enter>

2. Set up your local access password.  This password protects the Security
   accounts from unauthorized users.  When this protection is enabled, you 
   cannot view, modify, or tamper with the Security accounts unless you 
   enter the correct local access password.  The local access password must 
   be chosen and protection must be enabled before Dial Security is enabled.

   In the following example, the local access password is the same as the 
   password in account 0.

         AT%L=PW0 <Enter>

********************************
Set up Accounts for Remote Users
Once your account is configured and password protection has been enabled, 
you can set up the remote user accounts.  Use the %An= command (using the 
same guidelines you used to set up the system administrator’s account in 
Step 1 of the previous section) to set up remote user accounts.

Once security accounts have been enabled, you are responsible for 
communicating valid password information to your remote users.

********************
Enable Dial Security
Once you have completed the previous steps, you are ready to enable Dial 
Security.

When you enable Dial Security, you must choose either autopass or prompting 
as the security method.  You must know what types of modems remote users 
are using and set the Dial Security parameters accordingly.  Autopass is 
limited to U.S. Robotics modems with Dial Security, but prompting is not.

1. Register S53 is the bit-mapped register used to enable Dial Security.  
   The &W command must be used to save Register S53 settings to NVRAM.  
   Otherwise, when the computer is powered off and on again, or the modem 
   is reset using ATZ, it will default to S53=0, Dial Security disabled.

   To enable Dial Security with autopass and local access password 
   protection, but without prompting, type the following command:

         AT S53.0=1 .2=1 &W <Enter>

   The following command enables Dial Security with autopass, prompting, 
   and local access password protection.

         AT S53.0=1 .1=1 .2=1 &W <Enter>
  
   NOTE:  Enabling local access password protection disables the &Zn=s 
   command that stores up to ten phone numbers.  Stored phone numbers 
   occupy the same space in NVRAM as the dialback numbers for Dial Security 
   accounts, and cannot be used when Dial Security is enabled.

   If the local access password is not protected, the &Zn=s command 
   overwrites the corresponding Dial Security dialback number.  For 
   example, the following command overwrites the dialback number for 
   account 5:

        AT &Z5 = 555-8976 <Enter>

   However, if the local access password is protected, and a user tries to 
   use the &Zn=s command, an ACCESS DENIED message is displayed.

   WARNING:  Be sure DIP switch 10 is OFF so the modem will load the 
   settings stored in NVRAM.  If someone sets DIP switch 10 ON, the low 
   performance template settings (&F0) are loaded, and Dial Security is 
   disabled.  If this should happen, reset DIP switch 10 to OFF, power 
   off the modem and power it back on, or reset the modem by typing ATZ 
   <Enter> so that the proper settings take effect. 
   

**************************
Maintain Security Accounts
Once the local access password is set and protected, the system 
administrator is the only one who can access account information.  To 
modify or change account information, use the %S= and %E= commands 
described next.

Account Access (%S)
Once Dial Security is enabled, you can access accounts by entering the 
local access password using the %S= command, which allows access to the 
accounts by disabling local security.

       AT%S=(your local access password) <Enter>

NOTE:  The modem echoes the local access password, which is case sensitive.  
The system will accept an invalid password entry, but will lock you out 
from the modem’s security commands.  For example, if the password is Bob, 
but you enter BOB, an OK is displayed.  However, if you try to type a 
security command (for example, ATI10 <Enter> to view accounts), an ACCESS 
DENIED message is displayed. 

Account Status
Once access has been granted, you can view account information by typing 
the I10 option of the Inquiry (I) command:

        ATI10 <Enter>

Remote users may only use this command during a remote access session if 
local access security is disabled.

Erasing Account Information (%E)
Use the %E=n command to make system edits.
%E=1  Erase local access password. 
%E=2  Erase autopass password.
%E=3  Erase passwords in accounts 0-9.
%E=4  Erase phone numbers in accounts 0-9.
%E=5  Disable Account, Dialback, and New Number fields in accounts 0-9.

To edit or overwrite an individual account, or an individual account field, 
use the %An= command described in Set Up Your Security Account, earlier 
in this appendix.

Remote Configuration
Dial Security accounts may be configured remotely.  See Configuring Dial 
Security Remotely at the end of this appendix.


**********************************
WHAT THE REMOTE CALLER NEEDS TO DO

When remote users want to call in to your Courier (assuming you have 
enabled Dial Security), they must contact you to obtain a valid password.  
They must also find out if they must set the remote modem for auto answer 
(necessary if your modem uses Dialback as a security method).

1. If the host modem security is set up, get a password from the host 
   modem operator.  Passwords are case-sensitive, so be sure to copy it 
   down correctly.  

   If the host modem security is set up for prompting and the host 
   operator enables dialback for your account, skip to Step 3.

2. For remote users with COURIER modems only.  Set up security on your 
   modem, including an account that uses the password the host asked you 
   to use.  Refer to Set up Your Security Account, earlier in this 
   appendix, for instructions.  
   
   Then assign the password as your autopass password.  Enter the following 
   command, where n is the number of the account you set up):

           AT %V=PWn <Enter>

   You can check to see that you've correctly set up your autopass 
   password by typing the following command:

           AT I10 <Enter>

   Your autopass password appears in the right-hand column below FORCED 
   AUTOPASS.

   Once the autopass password is set, enable your Courier modem’s Dial 
   Security with the following command:

          ATS53.0=1 &W <Enter>

3. If Dialback is enabled at the host Courier site, set your modem to 
   answer the host modem when it disconnects and dials back.

   To set the modem to answer the Dialback call, set DIP switch 5 OFF 
   and reset the modem (ATZ <Enter>).

   Alternatively, type the following command:
 
          AT S0=1 <Enter>

4. Call the host modem.

5. When the call is completed, if you want to disable auto answer, do one 
   of the following:

   * Set DIP switch 5 ON and reset the modem (ATZ<Enter>).
   * Type the following command:

         AT S0=0 <Enter>



___________________________________________________________________________
REMOTE ACCESS OPERATIONS

You can set a Courier modem so that someone at a remote location can 
configure your modem.  

This might be helpful if you have problems making a connection with 
another modem.  For example, if you have trouble connecting with a 
bulletin board, you can allow the bulletin board operator to dial 
in to your modem and view its configuration settings.  If necessary, 
the bulletin board operator can send the Courier a configuration string 
that will make it compatible with the bulletin board.  

Another use might be for Dial Security administration when the system 
administrator is unable to be at the host modem site.  It might be urgent, 
for example, to disable an account.

*************************
AT THE HOST COUTRIER SITE

There are two tasks required to set up remote access:
1. Set up password security.
2. Enable remote access.

************************
Set Up Password Security
You can designate two passwords for remote access security, each allowing 
a different level of access to the remote user.  You can assign one 
password that allows viewing privileges only, whereby the host Courier's 
configuration can be remotely viewed but not changed.  You can assign 
another password that allows both remote viewing and configuration 
privileges.

Remote access passwords can be up to eight alphanumeric characters 
long, and are not case-sensitive.

%Pn   Use the %Pn command to assign remote privileges.
      %P0  Viewing privileges only
      %P1  Viewing and configuration privileges

To assign a password that allows viewing privileges only, use the command 
format below:  

        AT%P0=[password] <Enter>

To assign a password that allows viewing and configuration privileges, 
use the command format below:  

        AT%P1=[password] <Enter>


Disabling Password Security
If you want to disable an assigned password (and thereby disable remote 
access security), use the following command format:

          AT%P0= <Enter>
                or
          AT%P1= <Enter>

WARNING:  If you disable the %P1 password, a remote user does not need 
to enter a password for configuration access.

********************
Enable Remote Access
Set Register S41 for a value of 1 or greater.  S41 is used to set the 
number of allowable login attempts, as explained later.  A setting of 
zero allows no login attempts, and thus disables remote access.

          AT S41=1 <Enter>

NOTE:  This method will not work if your modem is attached to certain 
synchronous devices.  Refer to Appendix F for more information.

LED Indicator for Remote Access
The Courier's SYN status light indicator (LED) flashes to indicate when 
it is in a remote access session.


************************
AT THE REMOTE MODEM SITE

Remote configuration can be performed at any time during an asynchronous 
connection.  The user performing remote configuration can use any modem; 
it does not have to be a U.S. Robotics model.

1. Make sure the host Courier has been set for remote configuration, as
   described earlier.  Then establish a connection.  It does not matter 
   which modem originates the call.
2. After a connection has been established, send the following escape 
   sequence:

        Pause four seconds,
        type four tildes: ~~~~
        and 
        pause another four seconds.

   NOTE:  You can change the escape sequence character with Register S42.  
   The pause duration (guard time) can be modified with Register S43.  
   (These values are set at the host Courier modem.)

3. When the Courier begins its login sequence, the caller will see a 
   display similar to the following:

      U.S Robotics Courier HST Dual Standard V.34 Fax Remote Session
                   Serial Number 000000A000000001

4. At this point, if password security is active, the caller is prompted 
   for the password.  
   
      Password (Ctrl-C to cancel)?.....

   As described earlier in Password Security, entering the password 
   assigned by the %P0 command allows viewing privileges only.  Entering 
   the password assigned by the %P1 command allows viewing and configuration 
   privileges.  Note that there is a 3-minute time limit for entering the 
   password.

   As mentioned earlier, if the number of unsuccessful login attempts 
   exceeds the set limit, the modem returns online and refuses any further 
   login attempts during the remainder of that connection.  
   
   When a password is accepted, the Courier indicates that it has entered 
   Remote Access mode and the remote prompt appears on the remote caller's 
   screen.  
   
     Access Granted
     Remote->

5. If password security is not active (no passwords have been set or both 
   passwords are disabled), the Courier automatically enters Remote 
   Access mode and the remote prompt appears on the remote caller's 
   screen.

     Remote->

6. Once the remote access session has been established, keep in mind that
   there is a 3 minute inactivity timer.  If the modem detects no activity 
   for 3 minutes, it aborts the remote access session and resumes a normal 
   online connection.

Aborting the Request for Remote Access 
If you want to abort the remote access login before you have entered the 
password, return online by pressing <Ctrl>-C or typing ATO <Enter>.

********************************
Remote Viewing and Configuration
Once you've gained remote access, you can communicate with the host Courier 
as if you are entering commands at its attached computer.  Depending on your 
access privileges, you can use the regular Courier AT commands.

If you have view privileges only (with %P0), you can use any of the view 
(Inquiry) commands described in Chapter 6.

If you have view and configure privileges (set with %P1), you can use any 
of the modem commands, except those commands that cannot be used while 
online, such as the Dial command.  You can also use the remote 
configuration commands explained later.

When you make remote configuration changes, the remote prompt is altered to 
indicate that changes have been made.  The prompt will change from:

             Remote->
                to
             Remote+>

If you restore the original configuration (with %C1, explained next), the 
original prompt is also restored (back to Remote->), indicating that the 
original configuration is intact.

By default, configuration changes do not take effect until the connection 
is terminated (see %Cn).  However, the new configuration is immediately 
reflected on the information screens (ATIn).

*****************************
Remote Configuration Commands
There are some additional commands that are only executable during a remote 
access session.  These commands are as follows.

%Bn     Configure the Courier's serial port rate.  
        %B0   110 bps              %B6    9600 bps
        %B1   300 bps              %B7    19,200 bps
        %B2   600 bps              %B8    38,400 bps
        %B3   1200 bps             %B9    57,600 bps
        %B4   2400 bps             %B10   115,200 bps
        %B5   4800 bps

%Cn     Configuration control.
        %C0   Defer configuration.   This is the default.  Configuration 
              changes are deferred until the call is ended; they take effect 
              for ensuing connections.  You do not need to enter this 
              command; it is the default unless you enter %C1 or %C2.
        %C1   Restore configuration.  Use this command to cancel any 
              configuration changes made during remote access, and 
              restore the original configuration.  However, commands that 
              have been written to NVRAM (with &W) will not be restored to 
              their previous settings.  Additionally, if you have forced 
              immediate configuration changes (with %C2), those changes 
              cannot be reversed with %C1.
        %C2   Execute configuration.  Use this command to force 
              configuration changes to take effect immediately, 
              during the current connection.  We recommend against 
              forcing immediate configuration changes unless absolutely 
              necessary, as this can result in an unreliable connection 
              or even a loss of connection.

%Fn     Configure data format.
        %F0   No parity, 8 data bits.
        %F1   Mark parity, 7 data bits.
        %F2   Odd parity, 7 data bits.
        %F3   Even parity, 7 data bits.

Password Commands
%Pn=    Disables password security (n=0 or 1) when no character follows 
        the equal sign.

%Pn=s   Specify the following password string (s) for viewing privileges 
        only (n = 0) or view and configuration privileges (n= 1).        

%Pn?    Display password n.

Command Format
When typing commands during the remote access session, no delay between 
command strings is necessary.  For example, you can type the following 
commands without pausing after each one:

* a password:  ABCDEF <Enter>
* a configuration string: AT&H1&R2&W <Enter>
* and a request for an information screen: ATI5 <Enter>

The maximum number of characters between carriage returns is 40.  


Ending a Remote Access Session
One of four commands ends a remote access session.
* <Ctrl>-C aborts the login procedure.
* ATZ resets the modem and terminates the connection.
* ATH terminates the connection.
* ATO or ends the remote access session, but the modems remain online.

**********************************
Configuring Dial Security Remotely
The system administrator can configure host Courier security account 
information with a Courier modem at a remote site using the procedures 
described below.  

NOTE:  Before remote configuration is possible, the local modem's remote 
access must be enabled, and a remote access password that allows viewing 
and configuration privileges must be assigned.  For convenience, you may 
want to use your local access password as your remote access password.

Dialing In From the Remote Site
1. From the remote site, connect to the host modem using Dial Security.  
   Once a connection is made, follow the instructions for beginning a 
   remote access session as described earlier in this appendix.

2. When remote access has been granted, use the %S= command to access the 
   Dial Security accounts.

3. If you wish, you can view account information by typing the following 
   Inquiry (I) command:

         AT I10 <Enter>

4. Make any configuration changes and execute them immediately by typing 
   the following command:

        AT %C2 <Enter>

5. To end the remote session and reactivate local access security on the 
   host modem, reset the modem by typing:

        ATZ <Enter>

WARNING:  If you do not use the ATZ command to end a remote access session, 
local access security will remain disabled at the host Courier site and 
anyone dialing in to your modem for remote access will have access to the 
I10 screen and all Security accounts.

Appendix E--Troubleshooting


You may occasionally encounter one of the problems listed here.  They are 
divided into three categories:  Running the SDL.EXE Upgrade Program, Before 
Establishing the Link, and During Data Transfer.

***********************************
Running the SDL.EXE Upgrade Program     

Your modem . . .

Is indicating an error
   Try running the SDL program at a lower serial port rate.  If your 
   computer doesn’t have a 16550 UART, a slower serial port rate can 
   make all the difference.

   You can also try running the program on a different PC.  An 
   idiosyncracy of an off-brand PC or an uncommon version of DOS may 
   lock up the SDL program.

***************************
Before Establishing the Link    

Your modem . . .

Doesn't answer the phone or go off hook to dial a number
   Review your communications software manual to see what Data Terminal 
   Ready (DTR) operations your software requires.  Then check to see if 
   DIP switch 1 is set correctly.  Also, check to make sure your terminal 
   or computer is sending a DTR signal via the RS-232 interface.

Doesn't respond OK when you type AT <Enter>
   1. Make sure you're typing in either upper case or lower case letters, 
      not a combination, and that you press the Enter key.
   
   2. If you're using a computer, make sure it is in Terminal mode.  This 
      is a communications software function.  See Testing the Modem in 
      Chapter 2.
   
   3. Check to see that your terminal or software is set to the correct 
      bit rate and word length (7 bits with or without a parity bit, or 
      8 bits and no parity).  If you're using a computer, make sure your 
      software is set to the correct communications port.
   
   4. Check that DIP switch 8 is ON, for command set recognition.  If the 
      switch is OFF, power off the modem, set the switch ON, and power on 
      the modem again.  Try typing AT <Enter> again.
   
   5. Check that DIP switch 3 is ON, for result code display, and that 
      DIP switch 2 is OFF, for verbal result codes.  If not, change the 
      switch(es) and type ATZ <Enter>.  Or type whichever of these commands 
      is needed:

          ATQ0 <Enter>    (to enable the message)
          ATV1 <Enter>    (to display a verbal message)

   6. Review your communications software manual to see what Carrier 
      Detect (CD) operations your software requires.  Then check to see 
      if DIP switch 6 is set correctly. 
   
   7. A rare condition is that your terminal or computer reverses the 
      send/receive functions at the RS-232 interface.  See your equipment 
      documentation.

Displays double characters
   Both your modem's and software's local echo are on.  You can turn your 
   software's local echo off.  Or turn the modem's echo off by either 
   resetting DIP switch 4 and sending the modem the ATZ command, or by 
   sending the modem the ATE0 command.


Your computer . . .

Reacts as though a data link has been established, but no call has been 
received

   DIP switch 6 is set ON at the factory for Carrier Detect (CD) override, 
   but your system may require that the override be turned OFF.  
   
   Review your terminal's manual or your communications software manual to 
   see what CD operations are required.  Then check to see if DIP switch 
   6 is set correctly.

When the modem is in Answer mode, it acts as though a Carriage Return has 
been entered, but nothing has been typed at the keyboard

   Your software may be misreading signals from the modem as it 
   automatically sends a Carriage Return and a Line Feed before and after 
   the RING and CONNECT messages.  Sending the Quiet mode command, ATQ1 
   <Enter>, should solve the problem.


Both modems . . .

Exchange carrier signals, but fail to establish a communications link
   1. If you have a fax modem, make sure it is in the correct mode, fax 
      or data, depending on whether the connection is to be made with a 
      facsimile device or a data modem.  See Fax Operations in Chapter 5 
      for information on switching between Fax and Data modes.
   
   2. Asynchronous operations:  Check to make sure the proper bit rate, 
      word length, parity and number of Stop bits have been selected.  
      Synchronous operations:  review the link instructions in Appendix F. 
      If you've set the modem to the correct configuration, the problem may 
      be with the synchronous adapter or with the system you're trying to 
      call.
   
   3. Check to see that your modem is at the correct Bn setting to connect 
      with either an HST modem (B1 setting) or V.32 terbo modem (B0 setting).  
      Type ATI4 for a display of the Courier's current settings and, if 
      necessary, send the modem the correct setting.
   
   4. If your modem is attempting to answer a V.32 call, you may need to 
      lengthen the extra V.32 answer tones.  See S28 in Appendix B.
   
   5. Depending on your model, make sure the modem at the other end of the 
      line is HST compatible, V.32 terbo compatible at 14.4K bps, or V.32 
      compatible at 9600 bps, V.22 bis-compatible at 2400 bps, Bell 
      212A-compatible at 1200 bps, or Bell 103-compatible at 300 bps.  
      These are the common signaling standards for full duplex dial-up 
      network transmission in the U.S.
   
   6. Make sure your modem's connection rate setting, &Nn is correct for 
      the call.  If the connection rate is locked at a speed (&N1-&N14) 
      different from the calling modem's, the Courier hangs up.  The 
      factory setting of &N0, variable link operations, allows the two 
      modems to negotiate the highest possible connection rate.
   
   7. If none of the above corrects the problem, it's likely that the 
      quality of the phone connection is poor and that the other modem is 
      missing the signals your modem is transmitting.  The variable 
      quality of phone line connections may be due to any number of 
      conditions in the phone service's equipment or the current 
      environment.  Try several calls, and if you still can't get through, 
      try calling another modem.  If the second modem accepts your call, 
      the problem may lie with the modem you first tried to call.


********************
During Data Transfer

Your screen displays . . .

Only brackets
   Check to make sure that both modems are set to the same bit rate, word 
   length, parity and number of Stop bits.  If the settings are correct, 
   the problem may be with the phone line.  Try the following measures:
   
   1. Try placing the call again.  The phone company routes even local 
      calls differently each time you call.
   
   2. Try calling a different modem to see if the problem persists.  The 
      problem may be with the modem you first tried to call.

Random or garbage characters
   Check to make sure that both modems are set to the same bit rate, word 
   length, parity, and number of Stop bits.

   If the modem is set to a fixed serial port rate (&B1) and your software 
   is fixed at 19.2K, 38.4K, 57.6K, or 115.2K bps, the reason may be one 
   of the following:
   
   1. Your computer may not support the high rate.  If this is the case, 
      fix your software rate at 9600 bps and disable high-speed V.32 terbo 
      modulation: ATS34=3 or ATS34 .0=1 .1=1. 
   
   2. If you use memory-resident programs (TSRs), they may be interfering.  
      Try disabling them before you run your communications software.  
      The same is true of disk-caching programs.
   
   3. Check to see that your software and the modem are set for the same 
      kind of flow control, either hardware or software.  Some 
      communications programs also require that you disable the kind 
      you are not using.

Double characters
   Your modem's online local echo is on and the remote modem is also 
   echoing.  The only way to correct this is to bring the modem back 
   to Command mode (wait one second without transmitting data, type 
   +++, wait another second).  Then type the command to turn off your 
   online echo (ATF1 <Enter>).

   If DIP switch 9 is OFF (factory setting), the modem hangs up when it 
   returns to Command mode, and you'll have to call again.  If DIP switch 
   9 is ON, the modem maintains its connection.  You can return it back 
   online by typing ATO <Enter>.  
   

**************************
IF YOU STILL HAVE PROBLEMS      

The problems described above are by far the most common ones that users 
encounter.  If the suggestions we've given don't clear up your difficulties, 
try the following:

1. Review the manual carefully to see if you've missed something.

2. Call or visit your modem dealer.  Chances are your dealer will be able 
   to give you the assistance you need.  This is much more efficient and 
   time-saving than returning the modem to U.S. Robotics.

3. If your dealer can't help you, refer to the Customer Service Access 
   Card provided in this package.  This card lists several important U. S. 
   Robotics numbers.

4. If you must return your modem to us, the Service Representative you 
   talk to will give you a Return Materials Authorization (RMA) number.  
   Modems without an RMA number will not be accepted.

5. If you do return the modem to us, please use the following procedures.
   a. Ship the unit, postage paid, in its original container.  If the 
      original container is not available, pack the modem carefully in a 
      strong box of corrugated cardboard with plenty of packing material.
   
   b. Be sure to include your RMA number inside the package, along with 
      your name and address.  Put your return address and your RMA number 
      on the shipping label as well.
   
   c. Ship the well-packed modem to the following address.
   
           Technical Support Department
           U.S. Robotics, Inc.
           8100 North McCormick Boulevard
           Skokie, Illinois 60076-2999
   
   d. Please note that U.S. Robotics will not accept packages sent COD, 
      so be sure to send the modem postage paid.
   
   e. U.S. Robotics will repair your modem and return it to you via 
      United Parcel Service.

Appendix F--Synchronous and Dedicated Line Operations


___________________________________________________________________________
SYNCHRONOUS APPLICATIONS

Synchronous mode is required for users who need to call, or receive 
calls, from a Host computer of a large network.  The Host is usually 
a mainframe.  There are two ways the Courier can operate in synchronous 
mode:

* Selecting the ITU-T standard V.25 bis protocol, which formats data in 
  HDLC or character-oriented frames.  This method is used by mainframe 
  operators and synchronous terminal users.

  V.25 bis acts as an interface between the mainframe and modem, sending 
  synchronous responses.  An asynchronous device or a "dumb" terminal 
  is used to configure the modem before it dials out in synchronous mode. 

* Dedicating a PC as a synchronous device by installing the proper 
  hardware and software so it can communicate with a mainframe.  The modem 
  is configured and dials out in asynchronous mode, then switches to 
  synchronous mode once a connection is made.

NOTE:  HST modulation is not supported for synchronous communications.

********************
GENERAL REQUIREMENTS

Courier modems in asynchronous mode adapt to many conditions of remote 
asynchronous modems.  But synchronous connections to a mainframe require 
strict adherence to specific operating parameters.  If you are operating 
a terminal designed for a particular network, you probably need only set 
the Courier properly before calling or answering.

NOTE:  The term DTE in the following discussion means Data Terminal 
Equipment, the end-to-end equipment involved in data communications.  
DTE denotes your terminal or computer and the remote computer.

*********************
What You Need to Know
The network's communications management staff can supply information on 
the following requirements:
* The protocol needed for your calls
* The software support needed to log into the network; for example, a 
  specific communications package or interface board
* The phone number, if you will be calling instead of answering
* Any restrictions about when you can call

********************
The RS-232 Interface
Transmit and Receive synchronous timing pins are required at the RS-232 
interface.  You'll need either pin 15 or pin 24 for Transmitter timing 
signals, depending on whether the modem (pin 15) or the DTE (pin 24) 
generates the signals.  You'll also need pin 17, for Receiver timing 
signals.  If you're building your own cable, review the RS-232 Interface, 
in Appendix B.

**********************
Protocol Compatibility
The devices at both ends of the link must use the same protocol.  These 
protocols format data into blocks or frames and add control information.

If the modem is in V.25 bis mode, the link protocol must be HDLC 
(High-Level Data Link Control), or character-oriented.  If the modem 
is in Online Synchronous mode it may use HDLC, character-oriented, or 
another protocol determined by the mainframe manufacturer.  

******************************
Data Rate Synchronization (&Xn)
During synchronous operations, transmit and receive clocks at both ends 
of the phone link control the precise timing of the data flow.  The 
communications equipment at the remote DTE and your modem and DTE must 
all handle the data at the same speed.

The transmit clock timing signals setting, &Xn, determines whether the 
modem or DTE will generate the timing signals.  For Online synchronous 
operations, the source for this setting must be the same on both systems.  
See Connection Rate (%Nn, &Nn) later in this appendix.

Most Online synchronous users will require the default setting, &X0.

&X0  The Courier is the source of the Transmit clock timing signals and 
     sends them to your DTE over the RS-232 interface.  The DTE rate will 
     follow the connection rates.  Default.

&X1  The DTE is the source of the Transmit clock timing signals and sends 
     them to the Courier over the RS-232 interface.  This setting is used 
     typically in leased line multiplexed operations.  (Multiplexors divide 
     the phone channel so that the channel carries several calls at the 
     same time.)  
     
     The DTE ignores the Courier's clock timing signals and negotiates 
     the DTE and connection rates.

&X2  The Courier's Receiver clock is the source of the timing signals.  
     The signals are looped to the Transmit clock and sent to your DTE 
     over the RS-232 interface.  This setting is only used in those 
     systems that require synchronization of data flowing in both directions.


**********************
V.25 BIS RREQUIREMENTS

V.25 bis is an ITU-T standard that uses the HDLC or character-oriented 
protocols to format data.

Before you attempt to connect to a synchronous network, you must configure 
the modem in command (asynchronous) mode by using either an asynchronous 
device or dumb terminal.  V.25 bis commands are used for this purpose.  
The computer or terminal sends V.25 bis commands to the modem to ready 
the line for synchronous transmission.  Once the synchronous connection 
is made and the modem is in synchronous mode, V.25 bis commands are no 
longer necessary and are ignored.  The modems on each end of the 
connection are transparent to the host computers or terminals.

To set the modem, follow the instructions in Chapter 4, Command Set Usage.  
Commands begin with a required AT prefix and end with a required Carriage 
Return, which we denote with the symbol <Enter>.  For example, the 
following command causes the modem to set the connection rates, enable 
normal result codes, enable auto answer, select HDLC as a link protocol, 
and save the settings to NVRAM.  Spaces have been added only for 
readability.

        AT &N0 %N6 X0 S0=1 &M7 &W <Enter>

Be sure that DIP switch 10 is OFF so that the modem loads the settings 
you've stored in nonvolatile random access memory (NVRAM) when it 
powers on.  Until you customize your own settings, the settings in 
NVRAM are the same as the &F1 Hardware Flow Control template.

**************************
Connection Rate (&Nn, %Nn)
There are three phases to obtaining and maintaining a connection rate 
during synchronous communication.  

Clock Speed Control
The first phase is in deciding where the clock speed will be determined.  
(See Data Rate Synchronization, above.)

Offline Host/Modem Clock Speed
The second phase involves the data rate between the host computer or 
terminal and its modem during offline mode.  The %N command is used to 
set the clock speed between the modem and host, but this speed is only 
during offline mode, before the synchronous connection is made.  
The %Nn command works in conjunction with &Xn.  If the modem is set so 
that it is the source of the Transmit clock timing signals 
(&X0--default), the %Nn commands set the computer or terminal-to-modem 
V.25 bis clock speed.  If the modem is set to &X1, the computer is the 
source of the Transmit clock signals.  

If %Nn is set to 0 or 1, you will receive an error message, since they 
are not valid values.  The %Nn rates are as follows:
%N0   Reserved           %N6    9600 bps (default)
%N1   Reserved           %N7    12.K bps
%N2   1200 bps           %N8    14.4K bps
%N3   2400 bps           %N9    16.8K bps
%N4   4800 bps           %N10   19.2K bps 
%N5   7200 bps

Online Connection Rate
The &N command sets the data rate during the synchronous connection.

If &Nn is set for 2-10, the modem ignores the %Nn rate and follows 
the &Nn rate to set the Online connection rate.  The &Nn rates are 
as follows:
&N0        Variable (default)   &N6     9600 bps
&N1        Reserved             &N7     12K bps
&N2        1200 bps             &N8     14.4K bps
&N3        2400 bps             &N9     16.8K bps       
&N4        4800 bps                      (terbo-terbo only)
&N5        7200 bps             &N10    19.2K bps 
                                         (terbo-terbo only)

Recommended Settings
When the connection is made and the data rate is determined, host/modem 
rates may change dramatically to match the connection rate (when in 
online synchronous mode, the modem is transparent on the line).  To 
avoid this dramatic rate switching (which can be hard on some computers), 
we recommend that the modem be set with a fixed rate between the computer 
or terminal and modem (%Nn) and that the connection rate (&Nn) be set to 
the same rate.  

*****************
Result Codes (Xn)
The Courier displays normal or extended synchronous result codes, 
depending on the setting of the Xn command.  By default, the modem is 
set to X1 for extended result codes.  To change to normal result codes, 
set the modem to X0.

The normal result codes return messages such as VAL or INV (VALID or 
INVALID), whereas the extended codes offer explanations--
INVPS (INVALID Parameter Syntax Error).

**************************
Automatic Answering (S0=1)
When the Courier is operating in V.25 bis mode, it ignores the DIP 
switch 5 setting, which controls Auto Answer.  To set the modem to 
automatically answer incoming calls, set the modem to S0=1, so it 
answers on the first ring.  You can substitute a higher value.  See 
the S-Register summary in Appendix B.

Suppressing Auto Answer
To disable Auto Answer, set the modem to answer on zero rings, S0=0.

*************************************
Choosing a Synchronous Protocol (&Mn)
Once the &Xn, %Nn, &Nn, Xn, and S0 commands are configured, you must 
use the &Mn command to choose the HDLC or character-oriented link 
protocol so that your synchronous software can properly format its 
commands.

&M6     Use the character-oriented protocol for synchronous communications.  

        The Courier and the remote modem must use the same eight-bit data 
        format.  The character length must be 7 bits and either ODD or 
        EVEN parity (ODD is preferred), or 8 bits and NO parity.

&M7     Use the High Level Data Link Control (HDLC), an ITU-T standard 
        for synchronous communications.  HDLC ignores parity.


**********************************
V.25 bis Commands and Result Codes 

Commands
* CIC (Connect incoming call) Instructs the modem to answer an incoming 
  call.
* CRN (Call request using number provided )Instructs the modem to dial 
  the number following this command.

        Example:
                CRN18001234

* CRS (Call Request with memory location)Instructs the modem to dial a 
  number stored in memory.

        Example:
                CRS3

* DIC (Disregard incoming call)Instructs the modem to disregard an 
  incoming call--overrides auto answer for this call.

* PRNn (Program number)
Stores a number in NVRAM.

        Example:
                PRN3; 18001234

* RFN (Request list of forbidden numbers)Instructs the modem to list the 
  numbers with which the modem is unable to connect.

* RLN (Request list of stored numbers)Instructs the modem to list those 
  numbers previously stored in NVRAM.

Dial Options
0-9  Digits
&    Flash
:    Wait for dial tone
>    (Greater Than) separator
<    Pause
=    (Equal Sign) separator
P    Pulse
T    Tone
.    (Period) separator
-    (Minus) separator

Result Codes
* SFI (Call failure indication) with optional parameters:
     - CFAB (Abort call)
     - CFCB (Local modem busy)
     - CFET (Engaged tone)
     - CFFC (Forbidden call)
     - CFNS (Number not stored)
     - CFNT (Answer tone not detected)
* CFRT (Ring tone)
* CNX (Connect)
* LS (List of numbers)
* LSF (List of forbidden numbers)
* LSN (List of stored numbers)
* INC (Incoming call)
* INV (Invalid) with optional parameters:
     - INVMS (Message syntax error)
     - INVCU (Command Unknown )
     - INVPS (Parameter syntax error )
     - INVPV (Parameter value error )
*  VAL (Valid)

Commands and Result Codes NOT Supported
* CRI (Call request with identification number)
* PRI (Program identifier)
* RLI (Request list of identification numbers)
* RLD (List of delayed call numbers)

**********
Hanging Up
Since the modem cannot accept commands once it is connected in synchronous 
mode, you cannot use the ATH (hang up) command or the +++ escape sequence.

The only way for the modem to disconnect is to drop its DTR signal.  This 
is normally done with software.  However, if the modem is initially set 
to S32=6 when it is in asynchronous mode, the modem will reset when the 
voice/data switch is pressed, thus dropping DTR. 

******************************
Returning to Asynchronous Mode
Once you've completed a communication session, you can switch between 
synchronous and asynchronous modes by flipping DIP switch 10 OFF 
(factory settings, asynchronous mode) and then ON (NVRAM settings, 
synchronous mode if the modem is set to &M6 or &M7).

The modem cannot switch between synchronous and asynchronous while a call 
is connected.

*******************************
ONLINE SYNCHRONOUS REQUIREMENTS

Although personal computers do not usually support synchronous 
communications, they can be dedicated to do so.  If you have a personal 
computer you must find out what hardware and software you need before 
setting the Courier for synchronous calls.

****************************
The Synchronous Adapter Card
You will probably have to purchase and install a synchronous adapter 
card.  These cards are multifunction boards that provide the following 
functions:
* A synchronous port from the DTE to the modem

* One or more synchronous protocols.  Be sure to find out which protocol 
  the Host mainframe requires before you purchase an adapter.

* Additional software functions.  For example, you need to identify the 
  type of computer or terminal you are using to the mainframe software.  
  You will most likely also have to specify your application--that is, 
  identify the mainframe resources you want to use. 

*****************
Setting the Modem 
When the modem is set to Online Synchronous mode, it remains in command 
(asynchronous) mode until it makes a synchronous connection with a remote 
modem.  Upon connection, the Courier enters synchronous mode and sends 
synchronous timing signals to your DTE.

Because the modem will not accept commands when it is in synchronous mode, 
you will have to configure it in asynchronous mode before trying to connect 
to a synchronous network.

NOTE:  Be sure that DIP switch 1 is OFF (factory setting).  The Data 
Terminal Ready (DTR) override must be OFF so that the Courier detects 
when the DTE raises and lowers the DTR signal.

To set the modem, follow the instructions for issuing commands in Chapter 
4, Command Set Usage.  Commands begin with a required AT prefix and end 
with a required Carriage Return, which we denote with the symbol <Enter>.  

For example, the following command causes the modem to set the modulation, 
the connection rate, and choose a timing source.  Spaces have been added 
only for readability.

         AT B0 &N0 &X0 <Enter>


************************************
Modulation/Connection Rate (Bn, &Nn)
Use the following guidelines for your Courier type.  V.Fast Class does not 
support synchronous mode.

V.32 terbo modems
If the modem is connecting with another U.S. Robotics V.32 terbo modem, 
set both modems to B0 and to a variable connection rate, &N0.  The modems 
will connect at the highest possible rate.  

If the Courier V.32 terbo is to connect with a V.32 modem, set the Courier 
to B0 and try a variable connection rate first, &N0.  If that doesn't work, 
try a fixed connection rate of &N6 (9600 bps) or &N3 (2400 bps).

Modems in HST mode
HST modulation for synchronous communications is not supported.  

Dual Standard modems
Set the Dual Standard modem to B0.  Try a variable connection rate 
setting (&N0) first.  If that doesn't work, you may have to set a fixed 
connection rate, for example, &N6 (9600 bps).

NOTE:  If your modem is set to a fixed rate, and the remote modem is not 
set to the same rate, your modem hangs up.

*********************
Connection Rate (&Nn)
Use this command to set variable or fixed rates at the link interface.  The 
default is &N0, variable rate.  The Courier negotiates with the remote 
modem for the highest possible connection rate, depending on the 
capabilities of the remote modem.  If &N0 does not work, try a fixed 
rate.

NOTE:  The modem is not capable of connecting at 21.6K bps in synchronous 
mode.

When you set the modem to a fixed rate, it will only connect if the remote 
modem is operating at the same rate.  If not, your modem hangs up.

The fixed rate options are as follows:
&N0       Variable rate &N6     9600 bps
&N1       Reserved      &N7     12K bps
&N2       1200 bps      &N8     14.4K bps
&N3       2400 bps      &N9     16.8K bps 
&N4       4800 bps              (terbo-terbo only)
&N5       7200 bps      &N10    19.2K bps (terbo-terbo only)


*******************************
Generating Clock Timing Signals
The &Xn setting specifies whether the Courier or your DTE generates the 
Transmit clock timing signals for a synchronous call.  Most users will 
require the default setting, &X0.  See Data Rate Synchronization (&Xn), 
earlier in this appendix, for more information.


***********
Dialing Out
The modem's stored command feature (&ZC=s) allows you to configure the 
modem for a synchronous connection and to dial out to the Host computer 
by just pressing the voice/data switch.  Below are our recommended 
procedures.

1. If your communications software isn't running, load the program and 
   put the computer in Terminal mode, as described in Chapter 2.  
   Terminal mode allows you to send AT commands directly to the modem.

2. Using the guidelines in Chapter 4, store a command string (&ZC=s) 
   that configures the modem according to the Host computer's requirements.  
   In addition, include the &M1 command, to have the modem enter synchronous 
   mode, followed by the appropriate Dial string.  The following is an 
   example:

           AT &ZC = &F &X1 &M1 DT5551234 <Enter>

   In the example, &F sets the modem's defaults as those of the &F0 
   template settings, while &X1, which specifies the computer as the 
   synchronous timing source, is the only non-default setting used besides 
   synchronous mode (&M1).  Any non-default settings should follow the &F 
   command.  The Dial command should be the last entry before the Carriage 
   Return.  

3. Set the voice/data switch to option 9, so that the modem executes the 
   stored command string when you press the switch.  Type the following:

          ATS32 = 9 <Enter>

   NOTE:  If you usually use the voice/data switch for another purpose, 
   you can include the execute stored command option (S32 = 9) in the stored 
   command string.  However, the total number of characters in the string 
   may not exceed 30.  

   If S32=9 is used with the stored command string, it over-writes any 
   other S32 option.  Once the communication session is over, you will have 
   to reset S32 if you want to select another option.

4. Press the voice/data switch when you want to connect with the synchronous 
   Host computer.  You need not have your communications software loaded 
   at the time.

5. After the call, restore the modem to asynchronous operations by 
   powering it off and on again.


*********
Answering
To configure the modem for Answer mode using the voice/data switch, follow 
the instructions in the previous section, Dialing Out, but with these 
modifications:

* Insert S0 = 1 in the stored command, Step 2.  This sets the modem to 
  Auto Answer.

* Omit the Dial string shown in the same step (DT and phone number).  

If you don't wish to use a stored command and the voice/data switch, send 
the modem the appropriate configuration string, ending with &M1.  The 
following command adapts the dial-out command example.  Note again that 
all non-default settings follow the &F command.

          AT &F S0=1 &X1 &M1 <Enter>

The modem responds automatically to an incoming call, enters synchronous 
mode and, in this case (because it is set to &X1), waits for synchronous 
timing signals from your DTE.


**********
Hanging Up
The modem remains online until the remote modem disconnects or your 
software causes the DTE to drop the Data Terminal Ready signal (DTR).  
The Courier sends the NO CARRIER result code if result codes are enabled, 
and returns to asynchronous Command mode.

****************************
Testing and Inquiry Commands
The modem testing commands (&Tn) and inquiry commands (In) cannot be used 
when the modem is operating in synchronous mode.


**********************
ENABLING REMOTE ACCESS

Because synchronous equipment cannot use AT commands to configure modems, 
a special function was designed so the modem can receive AT commands 
remotely.  To do this, the modem must be placed in remote access mode 
with the voice/data switch.

Press and hold down the voice/data switch while powering on the modem.  
Pressing the switch during power-on causes the modem to perform its normal 
self-test, enable Auto Answer, enable Remote Access (by changing the S41 
setting to 1), and disable password security.

WARNING:  If you enable remote access by pressing the voice/data switch 
while powering on the modem, previously set passwords will be erased. 


________________________________________________________________________
DEDICATED AND LEASED LINE OPERATIONS

The following operations apply in installations where the modem's phone 
line is not part of a public-access switched telephone network.  Instead, 
the modem is connected to a special user-installed telephone line or a 
line that is leased from the telephone company.  These lines are often 
referred to as dedicated (to a pair of modems) or private lines.  

In both types of installation there is a continuous point-to-point 
connection between two modems.  No dialing of phone numbers is required.  
The modems may be in either Smart or Dumb mode (determined by the position 
of DIP switch 8).  

*******************************************
The User-Installed or Leased Telephone Line
User-installed lines are most commonly 2-wire lines, similar to the 2-wire 
lines that connect residential phones to the public switched network.  

If you are leasing a line from the telephone company, request a 2-wire 
line, the type of line the modem is designed to work with.  If the 
telephone company only makes a 4-wire line available, you'll need a 
4-wire to 2-wire converter at each end of the connection.  If the phone 
company does not install the converters, you will have to supply them.  

For optimal operations, we recommend that the physical length of these 
lines not exceed 5 miles.

*****************
Setting the Modem
If the Courier is set to &L1, as described in what follows, and the 
remote AT-compatible modem has a comparable setting, they automatically 
connect when they are powered on.  They also reconnect, without any 
operator intervention, if a disturbance on the line is severe enough 
to break the connection.  

Set the modem as follows:
1. Set your terminal or communications software to the rate at which you 
   want the modems to communicate.  For example, use a terminal/software 
   setting of 19.2K bps and, if both modems have the capability, they will 
   connect at 14.4K bps.  The following instructions assume that you are 
   familiar with the guidelines on using the &B and &H commands (Chapter 3) 
   and the &W command (Chapter 3).

2. Send the modem the following command:

        AT &B1 &S2 &H1 &L1 &W <Enter>

   &B1 fixes the modem's computer interface rate at the same serial port 
   rate you selected when setting up your communications software.  &S2 
   causes the modem to send a Clear to Send (CTS) signal only after it 
   sends the Carrier Detect (CD) signal, that is, only after it connects 
   with the remote modem.  (See the note that follows.)  &H1 enables 
   hardware (CTS) flow control.  
   
   &L1 forces the modems off hook at power on and enables them to 
   re-establish the connection should it be broken.  &W writes the 
   settings to nonvolatile memory (NVRAM) as power-on defaults.  
   
   NOTE:  We recommend using the &S2 setting to delay CTS until after 
   the connection is made, as a precaution.  If the modems are in the 
   process of connecting or reconnecting, the Courier interprets any 
   keyboard data entry, including an accidental key stroke, as a 
   key-press abort, and hangs up.  Delaying CTS until after carrier 
   detection prevents this from happening, for example, if you are typing 
   data to the remote modem when the modems momentarily disconnect and 
   begin to reconnect.  However, you have to set the modem for hardware 
   flow control, &H1.

   If your software or machine does not support Clear to Send (CTS), don't 
   include &S2 and &H1 in the command string as suggested above.  Follow 
   the Transmit Data flow control (&H) guidelines in Chapter 3.  But keep 
   in mind that if the modems fail to connect or reconnect, the reason 
   could be a key-press abort. 

3. Set the modem to load NVRAM settings at power-on, DIP switch 10 OFF.  
   It does not matter if the modem is in Dumb or Smart mode (DIP switch 8).

4. Decide which modem is to be the calling modem and which the answering 
   modem.  Set the answering modem to Auto Answer, DIP switch 5 OFF, and 
   the calling modem to Auto Answer suppressed, DIP switch 5 ON.

5. Power off and power on the modems.  This initiates the new DIP switch 
   settings and loads the power-on defaults, including &L1.  The modems 
   go off hook and establish the connection.

NOTE:  If the modems cannot restore the connection and you could not set 
the modem to &S2, the reason could be a key-press abort.  If the problem 
persists, however, you may need to call your telephone company to have 
them check your line.


Appendix G--Additional Operations


CONTENTS  
         HST Cellular
         Voice/Data (External Modems Only)
         Hewlett Packard 3000 Installations
         MI/MIC Operations (External Modems Only)


_______________________________________________________________________
CELLULAR OPERATIONS

This function applies to Dual Standard HSTs only.  HST cellular modems 
can be used to answer or originate calls, but are proprietary.  They can 
only connect with other U.S. Robotics Dual Standard modems with HST cellular 
capabilities.

To enable cellular mode, load the &F3 template settings by typing the 
following command:

       AT &F3 <Enter>

To save this as your power-on/default setting, type this: 

       AT &F3 &W <Enter>

The &F3 command sets the serial port rate to 19,200 bps, and formats the 
data for 8 bits, no parity and one stop bit.  The ini-tialization string 
sent to the modem by loading this template is shown below.

      AT B1 X7 S10 = 30 &B1 &L2 &H1 &I0 &R2

* B1--enables HST modulation 
* X7--displays extended result codes including NO DIAL TONE, RINGING, NO 
  ANSWER, and BUSY messages
* &B1--locks the serial port rate so that it remains higher than the 
  connection rate.
* S10=30--sets the modem to wait 3 seconds after loss of carrier before 
  hanging up.
* &L2--enables cellular mode
* &H1--enables hardware flow control
* &I0--disables software flow control
* &R2--sets the modem so it sends received data to the computer or terminal 
  when the Ready To Send (RTS) signal is high, only if the computer or 
  terminal supports RTS.

The modem uses the U.S. Robotics proprietary HST cellular protocol to make 
connections.  The call starts at 1200 bps, a V.42 error control connection 
is negotiated, then the modem switches to 4800 bps and begins measuring the 
line conditions.  Depending on line conditions, the modem decreases or 
increases its connection rate, to a minimum speed of 300 bps and a maximum 
of 12K bps.  If a connection terminates before data transfer is completed, 
the system tries to re-establish the link and complete the transfer. 

If a large number of blocks are being resent (shown by the ARQ LED flashing 
randomly; some software displays the blocks retransmitted in the file 
transfer window), you may want to reduce the packet size by doing the 
following:

1. Be sure DIP switch 9 is ON so that the modem remains online if it 
   receives +++.

2. If DIP switch 9 is OFF, switch it to ON and reset the modem by issuing 
   the ATZ command.

3. Send the modem the escape sequence by typing +++ so that the 
   transmission is interrupted, and wait 1 second.

4. Type AT S33=1 to reduce the packet size.

5. Then type ATO so that the modem returns online and continues to transmit.

NOTE:  HST cellular connections can only be made with other U.S. Robotics 
modems in HST cellular mode.  The modem cannot be used to place a voice or 
data call to another phone or modem when it is in this mode.


__________________________________________________________________________
VOICE/DATA (EXTERNAL MODEMS ONLY)

The voice/data switch is located on the modem's front panel.  While the 
switch's primary function is to toggle back and forth between voice and 
data communications, this feature also allows you to perform other 
functions at the touch of a switch.  Use Register S32 to select these 
functions, as shown in Table G.1.

Additionally, the Courier modem allows you to use the voice/data switch to 
set the modem for remote access if attached to certain synchronous devices.  
This is described in Enabling Remote Access in Appendix F.

NOTE:  Use the voice/data switch when the modem is in Command mode 
(offline).  If you press the switch while the modem is online, the modem 
hangs up and returns a NO CARRIER result code.  

**************************************************
VOICE/DATA OPERATIONS--S32=1, S32=2 or AT COMMANDS

When you install the Courier, you have the option of plugging your phone 
into the second modular jack of the modem so it's available for voice calls.  
You can also switch between the phone and modem during a call.

If the remote modem has handset exclusion, you can change from voice to 
data and back again, with or without issuing a command.  

Handset exclusion means that if the modem is using the phone line, your 
phone (handset) is automatically disconnected.  However, if you keep 
the handset off hook, once you hang up the modem the handset takes over 
the phone line and you can use voice communications again.  If the remote 
user does not have handset exclusion, you may not be able to switch back 
to voice mode successfully once you have switched to Data mode.

The following instructions describe how to toggle voice/data communications 
with the switch.  This is followed by instructions for doing the same 
thing with AT commands.  If the remote user does not have a switch, he 
or she can follow the instructions for using the appropriate AT command.

*******************************
Voice/Data Switch--S32=1, S32=2
1. Phone the other user to establish the bit rate, parity, word length 
   and number of Stop bits the other person's modem accepts.  (Both 
   modems should be offline, in Command mode.)

   You and the other user must also agree on which modem will go off hook 
   in Originate mode and which in Answer mode.  The Courier is factory 
   set to go off hook in Originate mode, S32=1.  The Answer modem should 
   have S32 set to 2.

   NOTE:  If the stored command string command has been used (&ZC=s), the 
   modem will default to S32=9, which executes the stored command string 
   when the voice/data switch is pushed.

   Either party's device can be the originate or answer modem;  it doesn't 
   matter who made the phone call.  But one modem must first enter 
   Originate mode and the other then enter Answer mode.  
   
2. Without hanging up the phone, press the voice/data switch.  

   If S32 is set to 2, Answer mode, press the voice/data switch immediately 
   after the remote user forces the remote modem off hook in Originate mode.

3. The other party should force the remote modem off hook in Answer mode 
   by pressing the switch.

   If yours is the Answer modem (S32=2), the other party should press the 
   voice/data switch immediately before you do so.

4. If the remote modem has handset exclusion, the remote user should also 
   keep the phone off hook in order to switch back to voice later.  If the 
   remote modem doesn't have handset exclusion, you can try to switch back 
   to voice later.  Or, you both can hang up your phones as soon as the 
   modems go off hook.  

***************************
Software Commands--ATD, ATA
If your voice/data switch is set for a function other than voice/data 
operations and you don't wish to change it, use AT commands.  

1. Call the other user to establish the bit rate, parity, word length and 
   number of Stop bits the other person's modem accepts.  Determine which 
   modem will originate and which will answer.

2. If you are to originate the connection, type the following command:

          ATD <Enter>
 
   NOTE:  Be sure the modem is not set to X2, X4, X6 or X7, or it will 
   return the NO DIAL TONE result code and hang up.

3. The other party must then have the remote modem go off hook in Answer 
   mode.  The following command is used to do this:

           ATA <Enter>

4. If the remote modem also has handset exclusion, leave both phones off 
   hook in case you wish to switch back again to voice after your data 
   transfer.  If the remote modem doesn't have handset exclusion, switching 
   back to voice may not be successful.  If you don't want to switch back 
   to voice later, hang up both phones as soon as the modems go off hook.


*************************************
ALLOWABLE VOICE/DATA AWITCH FUNCTIONS

Use Register S32 to set the voice/data switch for the function you desire.  
The default is S32=1--pressing the switch forces the modem off hook in 
Originate mode.  Pressing the switch when you power on the modem causes 
it to perform a power-on self-test.  See Table G.1--S32 Functions below.

NOTE:  Some of the applications listed below require some sort of 
preconfiguration.  Review the Chapter/Appendix referenced before using 
the Voice/Data switch function.


Table G.1--S32 Functions   

S32                
Value   Voice/Data Switch Function             Related Command
   
 0      Disabled                               --      
   
 1      Voice/Data--Originate Mode (Default*)  ATD (Appendix G)
   
 2      Voice/Data--Answer Mode                ATA (Appendix G)
   
 3      Redial Last Number                     ATDL (Chapter 4)       
   
 4      Dial Number Stored at position 0       ATDS0 (Chapter 4)      
   
 5      Auto Answer On/Off Toggle              ATS0=0 or 1 (Chapter 4)        
   
 6      Reset Modem                            ATZ (Chapter 4)        
   
 7      Initiate Remote Digital Loopback       AT&T6, S16=8 (Appendix H)   
   
 8      Busy Out Phone Line Toggle              --      
   
 9      Execute Stored Command (Default*)       AT&ZC=s (Chapter 4, 
                                                   Appendix F, G)

* The modem is shipped from the factory set at S32=9.  If a command string 
  has been stored (&ZC=s), the modem executes the stored command string 
  when the voice/data switch is pushed.  If no command string is stored, 
  the modem still reports that S32=9, but actually behaves as if it is set 
  to S32=1, Originate mode.


__________________________________________________________________________
HEWLETT PACKARD INSTALLATIONS

During error control connections, the Courier recognizes the ASCII ENQ/ACK 
characters exchanged between many Hewlett Packard host computers and their 
terminals.  The HP host sends the terminal an ENQ character at predefined 
intervals, and sends no more data until the terminal responds with an ACK 
character.

Courier modems manage this ENQ/ACK protocol so that communication is 
speeded up, thereby enabling HP terminals to achieve high speeds on 
dial-up lines.  Special flow control settings, using the &I command, 
are required for HP users.  These settings apply to ARQ connections only 
and to Courier modems set to either B0 or B1.  Disregard other Courier 
flow control commands.

Set the Courier to Host mode if it is attached to the host computer, or 
to Terminal mode if it is attached to a terminal, as follows:

     Host mode       AT&I3 <Enter>
     Terminal mode   AT&I4 <Enter>


___________________________________________________________________________
MI/MIC OPERATIONS (EXTERNAL MODEMS ONLY)


Mode Indicate/Mode Indicate Common (MI/MIC) closure is required by some 
installations whose existing hardware does the dialing.  The modems do 
not Auto Dial.

In these situations, the modem must be forced off hook in Originate mode.  
This is done by shorting (closing) two of the pins (not Tip and Ring) in 
the phone connector.  The modem is then ready to go online and accept data 
when it connects with the number dialed by the system equipment.

Courier modems are shipped with MI/MIC disabled, that is, for normal use.  
To set the modems for MI/MIC closure, you must do two things:  physically 
set jumpers on the modem’s printed circuit board, and enable bit 5 of 
Register S34 (ATS34=32 or ATS34.5=1).  We recommend you then write that 
setting to NVRAM as a power-on default.

Once you've set Register S34, have the system force the modem off hook 
by closing the MI/MIC leads in the phone line connector.  The modem's OH 
(Off Hook) status light, or LED, goes on when the modem goes off hook.  

***************************
SETTIING THE MI/MIC JUMPERS
You'll have to dismantle the modem case to set the two jumper switches on 
the printed circuit board, as follows:

1.  Power off the modem and disconnect all of its cables.

2.  Turn the modem upside down.  Remove the two square vinyl feet near 
    the back of the case, on either side of the bottom label's DIP switch 
    diagram.  Be careful to put the vinyl feet aside, upside down, where 
    they won't become stuck to another object.

3.  Remove the two Phillips screws located in the wells beneath the vinyl 
    feet.  

4.  Gently pry off the plastic volume slide-switch cover.

5.  Raise the back end of the case bottom until it is at about a 60 degree 
    angle; lift it away from inside the front of the modem.  Put the case 
    bottom aside.

6.  Locate the voice/data switch at the front of the modem.  Lift up and 
    remove the modem (printed circuit board), carefully easing the 
    voice/data switch out of its opening in the front panel.

7.  Turn the modem rightside up and locate jumper switches J4 and J6, 

8.  The jumpers are black shunts that cover two out of three upright metal 
    contacts.  As shown in the figure, set the jumpers so they cover the 
    two contacts on each switch that are closest to the front panel.  The 
    third contact on each switch is exposed.

9.  Replace the modem in the case top:  ease the voice/data switch into 
    the opening in the front panel and make sure the back of the board 
    rests on the locator pins at the rear (from which you removed the 
    screws).

10. Connect the modem's RS-232, power and phone cables, in that order 
    (see Chapter 2).  Be sure the phone cable is plugged into the jack 
    closest to the center of the modem--the jack represented by the wall 
    jack icon on the case bottom label.  
   
    CAUTION:  When you power on the modem there will be potentially 
    hazardous voltage, particularly near the phone jacks.  Do not touch 
    the board when the power is on.

11. Power on the modem.  Try MI/MIC closure.  Check to see that the Off 
    Hook (OH) status light goes on.  If you dialed a number, listen for 
    an answer tone from the remote modem.  Then drop the DTR signal.  The 
    modem should go on hook and the OH status light should go off.  

12. When you are sure the equipment is working correctly, disconnect the 
    modem's RS-232, power and phone cables, and replace the bottom of the 
    modem case.  Ease the two nibs near the front corners into their 
    openings in the front of the case top, guide the rectangular slot 
    over the volume switch, and ease the back of the case bottom into 
    place.  Replace the two screws, the two vinyl feet, and the volume 
    slide-switch cover.  
    
***************
TROUBLESHOOTING

You may find that the modem does not respond to MI/MIC closure, which you 
can monitor by observing the LED.  Or the modem may fail to go back on hook 
when the computer or terminal drops the Data Terminal Ready (DTR) signal.  
The probable reason for either of these conditions is that your phone 
equipment reverses MI/MIC polarity.  

It's possible to solve this problem by reversing the modem's MI/MIC wiring.  
You'll have to dismantle the modem case again and reset the two jumper 
switches on the printed circuit board, as follows:

1. Lift off the jumpers from J4 and J6.  Reverse the positions.  That is, 
   on each switch, cover the center and rightmost contacts.  Make sure 
   the jumpers cover two contacts on each switch, or you'll disable the 
   MI/MIC function.

2. Replace the modem in the case top:  ease the voice/data switch into 
   the opening in the front panel and make sure the back of the board
   rests on the locator pins at the rear (from which you removed the 
   screws).

3. Reconnect the modem's RS-232, power and phone cables, in that order.  
   Be sure the phone cable is plugged into the jack closest to the center 
   of the modem--the jack represented by the wall jack icon on the case 
   bottom label.  
   
   CAUTION:  When you power on the modem there will be potentially 
   hazardous voltage, particularly near the phone jacks.  Do not touch 
   the board when the power is on.

4. Power on the modem.  Try MI/MIC closure again.  Check to see that the 
   Off Hook (OH) status light goes on.  If you dialed a number, listen for 
   an answer tone from the remote modem.  Then drop the DTR signal.  The 
   modem should go on hook and the OH status light should go off.  

5. If closure is not working properly, review the steps in this section.  
   Be sure the jumper switches are in the correct positions.  If you still 
   have problems, there may be a problem with the phone cable.  Or there 
   may be a problem with your hardware.

6. When the equipment is working correctly, disconnect the modem's 
   RS-232, power and phone cables, and replace the bottom of the modem 
   case.  Ease the two nibs near the front corners into their openings 
   in the front of the case top, guide the rectangular slot over the 
   volume switch, and ease the back of the case bottom into place.  
   Replace the two screws, the two vinyl feet, and the volume slide-switch 
   cover.


Appendix H--Modem Testing

Testing is available with the &T command or Register S16.  All loopback 
testing conforms to ITU-T Recommendation V.54.  Earlier U.S. Robotics high 
speed modems, however, did not perform the &T test repertoire.  

Only one test can be performed at a given time.  If you send a test 
command while the modem is in test mode, you'll receive an ERROR message. 

NOTE:  Testing is not available when the modem is in synchronous mode:  
&M1, &M6, &M7.


***************
Testing With &T
The tests supported through the &T command include analog loopback, digital 
loopback and remote digital loopback.  Users can key in their own data 
during testing, or use the modem's internal test pattern and error detector.  
In all cases, disable error control before testing.  If the modem is 
detecting errors and retransmitting the affected data, your results will 
be invalid.

During testing, the MR status light flashes.  

***********************
Ending a Test--&T0, S18
Issuing the &T0 command terminates a test.  Alternatively, set Register 
S18 to a specified number of seconds, for example, S18=10.  When the 10 
seconds are up, the modem automatically ends the test and returns to 
Command mode.  If the test was Analog Loopback, the &T0 command hangs up 
the modem.  If the test was Digital or Remote Digital Loopback, issue an 
ATH command to hang up the modem, or an ATZ command to hang up the modem 
and reset it to its defaults.

NOTE:  If you use the S18 test timer, but in the process of testing you 
issue an ATZ command, S18 resets to zero and the timer is disabled.  You cannot store a value for S18 in nonvolatile memory;  its power-on and reset default is always zero.

*************************
Analog Loopback--&T1, &T8
This test checks the operation of the modem's transmitter and receiver.  

There are two analog loopback options.  The first, &T1, involves your 
typing data that you can verify at your screen.  

The second option, &T8, is an internal self-test that does not involve 
the keyboard or screen.  It isolates the modem from the computer 
interface to give you a more specific result. 

NOTE:  Dual Standard modems must be set to B0 (default) or tested at 
2400 bps or lower to avoid HST asymmetrical modulation at higher speeds.

***
&T1
1. If you are testing an HST or Dual Standard modem, set your terminal or 
   software to 2400 bps.

2. The modem must be in Command mode.  If you wish, set Register S18 as a 
   test timer, as explained earlier. 

3. Send the modem the following command:
   
           AT &M0 &T1 <Enter>

   The modem disables error control, enters analog loopback (AL) mode, and 
   sends a CONNECT message.  The MR status light flashes. 

4. Type recognizable data so that you can verify it when it is looped back 
   to the screen.

5. End the test.  If you set S18, the modem automatically stops the test 
   at the timeout, exits AL mode and responds OK.

   If you didn't set Register S18, wait one second and type +++ to bring the 
   modem back to Command mode.  If DIP switch 9 is OFF, the modem also 
   hangs up and ends the test.   
   
   If DIP switch 9 is ON, type AT&T0 to end the test.  Or send either ATH 
   or the command that resets the modem, ATZ.  The latter two commands end 
   the test and hang up the modem.  The modem responds OK.  If the modem 
   sends an ERROR message, you have issued an invalid command.

6. If there were no errors, reset the modem to &M4, for error control, 
   unless you've issued the ATZ reset command. 

   NOTE:  If the modem is in online-command mode, that is, still connected 
   to a remote modem, and you send it an &T1 or &T8 command, it drops the 
   call, enters AL mode, sends a CONNECT result and waits for loopback 
   characters.


***
&T8
This AL option causes the modem to send an internal test pattern to its 
transmitter and loop it back to the receiver.  An internal error detector 
counts any errors and, when the test is ended, sends the number of errors 
or 000 (no errors) to the screen.

Since you don't type anything during this test, and the modem does not send 
anything to the screen, this option verifies only the modem.  If there are 
no errors but your problem continues, it may be at the computer interface.

1. If you are testing an HST or Dual Standard modem, set your terminal 
   or software to 2400 bps.

2. The modem must be in Command mode.  If you wish, set Register S18 as a 
   test timer, as explained earlier. 

3. Send the modem the following command:  

        AT &M0 &T8 <Enter>

   The modem disables error control and enters AL mode.  The MR status 
   light flashes.  The modem sends its internal test pattern to the 
   transmitter, and loops the pattern back to the receiver.  You will 
   not see any data on your screen.  
   
4. End the test.  If you set S18, the modem automatically stops the test 
   at the timeout.  If you didn't set Register S18, type AT&T0 to end the 
   test.  Or use ATH or the command that resets the modem, ATZ.  Both of 
   the latter end the test and hang up the modem.

   The modem hangs up and returns a three-digit code, followed by OK.  A 
   code of 000 indicates no errors were found.  A code of 255 indicates 
   255 or more errors.  An ERROR message indicates that you issued an 
   invalid command.

5. If there were no errors, reset the modem to &M4 for error control 
   unless you issued the ATZ command.

***
&T2
This option is reserved. 

*********************
Digital Loopback--&T3
If your modem has passed the AL test, this test can help you locate 
a problem with a remote modem or the telephone channel.  

NOTE:  This test requires the modem to establish a connection and return 
to online-command mode in response to the +++ escape code.  DIP switch 9 
must be set ON so that the modem does not hang up on receipt of the escape 
code.  After you change the switch, issue ATZ to the modem to initiate 
the new setting.

As with AL testing, HST and Dual Standard modems should be tested at 
2400 bps or lower.

1. Set the modem to &M0, to disable error control.  HST and Dual Standard 
   modems should be set to 2400 bps or lower to avoid asymmetrical 
   modulation at higher speeds.  Establish a connection with the remote 
   modem.

2. Bring the modem back to Command mode with the +++ escape code.  Then 
   send it the AT&T3 command.  The modem enters DL mode and the MR 
   status light flashes.

3. The remote user should type a short message.  It will be looped back 
   by your modem's transmitter for verification on the remote screen.  
   You will not see the message or any other data.

4. When the remote user has completed the test, issue the AT&T0 command 
   to end the test.  Or send either ATH or the command that resets the 
   modem, ATZ.  The latter two commands end the test and hang up the 
   modem.  The modem responds OK.  If the modem sends an ERROR message, 
   you have issued an invalid command.  

5. Reset DIP switch 9 OFF if you normally use the factory default.  Reset 
   the modem to &M4 unless you used the reset command, ATZ.  


********
&T4, &T5
The &T4 option causes the modem to grant a remote modem's request for a 
Remote Digital Loopback test.  

The &T5 option cancels &T4, and the modem fails to recognize such a 
request.  This is the default so that your modem isn't subject to 
another user calling and tying up your modem without your permission.

*********************************
Remote Digital Loopback--&T6, &T7
This test, like the local digital loopback test, verifies the condition of 
both modems and the phone link. 

The request for and granting of Remote Digital Loopback testing requires 
that both modems use ITU-T V.22 standard signaling.  The test must be 
performed at 2400 bps or lower.  If the remote modem does not have the 
capability or is not set to respond (&T4), you will get an ERROR result 
code.

As with Analog Loopback, there are two Remote Digital Loopback options.  
If you select &T6, you send keyboard data to the modem and verify it 
when it is returned over the phone lines and to your screen.  If you 
select &T7, the modem sends its internal test pattern and returns an 
error count to your screen.  

NOTE:  Both test options require the modem to establish a connection and 
return to online-command mode in response to the +++ escape code.  DIP 
switch 9 must be set ON so that the modem does not hang up on receipt 
of the escape code.  If necessary, set the switch ON and then issue the 
ATZ command to the modem to initiate the new switch setting.

***
&T6
1. Set the software to 2400 bps or lower.  Set the modem to &M0.  If you 
   wish, set the S18 timer.  

   Establish a connection with the remote modem.  If you haven't already 
   done so, arrange with the remote user to cooperate with your testing 
   and, if necessary, set the remote modem to acknowledge the RDL request.  
   For example, older U.S. Robotics high speed modems need to be set to 
   S16=8.

2. Bring the Modem back to Command mode with the +++ escape code.  Send it 
   the AT&T6 command.  The modem enters RDL mode and the MR status light 
   flashes.

3. Type a short message.  It will be looped back to your modem by the 
   remote modem and to your screen for verification.  (The remote user 
   will not see your data.)

4. End the test.  If you set Register S18 the modem automatically ends the 
   test when the test timeout is reached.  If you didn't set S18, type AT&T0 
   to end the test.  Or send either ATH or the command that resets the modem, 
   ATZ.  The latter two commands end the test and hang up the modem.  The 
   modem responds OK.  If you issue an invalid command, the modem sends an 
   ERROR message.

   Data errors indicate a problem with the remote modem or the phone link.  
   If you have not performed analog loopback testing with your modem, the 
   problem may also lie with your modem.

5. Reset DIP switch 9 OFF unless you normally set that switch ON, and issue 
   ATZ to the modem to initiate the new setting.  Reset the modem to &M4 
   unless you used the reset command, ATZ.  

***
&T7
This test option causes the modem to send an internal test pattern through 
the Remote Digital Loopback.  An internal error detector counts any errors 
and, when the test is ended, sends the number of errors or 000 (no errors) 
to the screen.

You don't need to type anything during this test.  The modem sends only 
its final error count to your screen.

1. Set the software to 2400 bps or lower.  Set the modem to &M0.  If you 
   wish, set the S18 timer.

   Establish a connection with the remote modem.  If you haven't already 
   done so, arrange with the remote user to cooperate with your testing 
   and, if necessary, set the remote modem to acknowledge the RDL 
   request.  For example, older U.S. Robotics high speed modems need to 
   be set to S16=8. 

2. Bring the modem back to Command mode with the +++ escape code.  Then 
   send it the AT&T7 command.  The modem enters RDL mode and the MR 
   status light flashes.  

   The modem sends its internal test pattern to the remote modem, which 
   loops it back to your modem.  You will not see the data on your screen.

3. End the test.  If you set S18, the modem automatically stops the test 
   when the timer times out.  If you didn't set Register S18, type AT&T0 
   to end the test.  Or send either ATH or the command that resets the 
   modem, ATZ.  The latter two commands end the test and hang up the modem.  
   The modem responds OK.  If you issue an invalid command, the modem 
   sends an ERROR message.

   When you terminate the test, the modem returns a three-digit code, 
   followed by OK.  A code of 000 indicates no errors were found.  A code 
   of 255 indicates 255 or more errors.  
   
   If you've performed an Analog Loopback and know your modem is working 
   properly, errors indicate a problem with either the phone connection 
   or the remote modem.

4. Reset DIP switch 9 OFF unless you normally operate with it ON.  Issue 
   an ATZ command to initiate the new switch setting.  Reset the modem to 
   &M4 unless you've sent it the ATZ reset command.  


*************************
TESTING WITH REGISTER S16

Register S16 is a bit-mapped register with the following bit functions:

        Bit     Value   Function
        0       1       Analog Loopback (AL)
        1       2       Dial Test
        2       4       Test Pattern
        3       8       Remote Digital Loopback (RDL)

NOTE:  Earlier U.S. Robotics modems require bit 3 to be enabled in order 
to grant RDL to a remote modem.  The modem now requires its default &T4 
setting instead.  To perform RDL with a U.S. Robotics modem that does 
not use the &T test repertoire, that modem should be set to S16=8 before 
it can grant RDL testing.

****************************
Analog Loopback (AL)--S16=1D
As with the &T AL test, do not attempt this test under error control.  HST 
and Dual Standard modems should be tested at 2400 bps or lower, to avoid 
asymmetrical modulation at higher speeds. 

To use the modem's Test Pattern (S16, bit 2) instead of typing your own 
data, see Test Pattern--S16=4 later in this appendix.

1. To initiate testing, type AT&M0S16=1D.  The modem disables error control, 
   enters AL mode and sends a CONNECT result code.  The MR status light 
   flashes.

2. Type data to the modem for the modem to transmit, loop to its receiver, 
   and output to the screen.  An alternative is to use the Test Pattern, 
   described later. 

3. End the test by not typing anything for one second, then typing three 
   pluses (+++), and waiting another second.  This forces the modem back
   to Command mode.  If DIP switch 9 is OFF, the modem exits AL mode and 
   returns to Command mode.  If DIP switch 9 is ON, the modem maintains 
   the connection when it receives the +++ escape code.  Issue the ATH 
   command to end AL mode.  

4. Reset the modem to Data mode, S16=0, and error control (&M4), or issue 
   the ATZ (reset) command.


****************
Dial Test--S16=2
The Dial Test is used for factory testing the frequencies of tone values.  
When S-Register 16 is set to 2 and a single tone is dialed (e.g., ATD7 
<Enter>), the modem continues to transmit that tone until you type another 
Carriage Return.


*******************
Test Pattern--S16=4
The test pattern can be used instead of your typed data during Analog 
Loopback (AL) or Remote Digital Loopback (RDL), using &T commands or S16.  
The test pattern is available at all speeds.  At 300 bps, the modem's 
serial port rate must be fixed (&B1) and the link rate fixed at 300 bps 
(&N1).  At rates over 9600 bps, just set the modem for a fixed serial 
port rate (&B1).

To use the test pattern during AL testing with S16, type the following 
command.  The test pattern is sent through the loopback.

           AT&M0S16=5D

To use the test pattern during RDL testing with S16, type the following 
command: 

           AT&M0S16=12 

To use the test pattern with the &T AL or RDL tests, insert the test 
pattern command, S16=4, before issuing the test command.  The first of 
the following commands initiates AL, the second RDL: 

           ATS16=4&T1
           ATS16=4&T6

The test pattern alone (ATS16=4) is used for testing equipment and the 
phone line.  When S16 is set to 4, the modem transmits the test pattern 
upon connection with a remote modem.  


Ending Testing with the Test Pattern
Pressing any character key cancels all test pattern tests and hangs up the 
modem.  If you used Register S16, be sure to reset Register S16 to Data 
mode when you reset the modem to its error control defaults, for example, 
ATZ or AT&M4S16=0.  

******************************
Remote Digital Loopback--S16=8

Responding Modem 
The responding modem must be ready to act on the Courier's RDL request.  
U.S. Robotics high speed modems should be set to &T4.  If they do not 
have &T testing capability, they should be set to S16=8.

Initiating Modem
1. If DIP switch 9 is OFF, set it ON so that it does not hang up on 
   receipt of the +++ escape code.  Issue an ATZ command to initiate the 
   new switch setting.

2. Set the software to 2400 or 1200 bps.  The ITU-T-specified RDL signals 
   are defined only for connections at 2400 or 1200 bps.

3. Disable error control by setting the modem to &M0.  Then establish a 
   connection with the remote modem.

4. Bring the modem back to Command mode by sending it the escape code:  
   one second of no data, three pluses (+++), and another second of no 
   data.

5. When the OK result code appears, send the modem the following command:

           ATS16=8 O

   The modem enters RDL mode (S16=8), the MR status light flashes, and the 
   modem goes back online (O command).  Then it transmits the ITU-T-defined 
   RDL signals, causing the remote modem to enter RDL mode.

6. Type any data at the keyboard.  (Or send the test pattern.)

7. To end the test, send the modem the +++ escape code again to bring it 
   back to Command mode.  

8. When the modem sends the OK result, reset the modem to Data mode with 
   the following command:

          ATS16=0
 
   The modem signals the responding modem that RDL testing is over.  
   Terminate the call as you normally would, and reset the modem to its 
   normal error control setting, &M4 or &M5.

   Or, if you wish to resume data transmission with the remote modem, add 
   the O command to the ATS16=0 string to return the modem online.  Keep in 
   mind, however, that error control is disabled.  Because error control 
   is negotiated during the connection sequence, its status cannot be 
   changed until the modem is back on hook and in Command mode.


Appendix I--Software Upgrades

     
The Courier V.34 modem is software upgradable.  You can download upgrades 
from the USR Bulletin Board Service (BBS) to obtain maintenance fixes or 
new features. 

We suggest you retain a copy of the most recent upgrade on disk so you can 
download it to your modem again, should the modem lose its code for any 
reason. 

The software download program requires DOS version 3.0 or higher and may 
be run from the DOS shell under Microsoft Windows.

****************
Call the USR BBS
1. Call the USR BBS:

         ATDT 708 982 5092 <Enter>

2. Unless you are running an ASCII-based communications program, answer 
   YES at the graphics prompt when you connect to the BBS.

3. Press Enter with each prompt until you come to the main menu.

*************************
Download the Upgrade File
1. At the command line of the main menu, type F (File) and press Enter.  
   Select area 5 (Courier) from the file area menu  The most recent 
   zipped files will display.  

2. Use the Enter key to scroll through the list and use the spacebar key 
   to highlight a file. 

   Scroll through the list and highlight the file named USRSDL.EXE.  
   Press Enter when it is highlighted to flag the file for download.

3. Press Enter to go back to the main menu.

4. At the command line on the main menu, type D and press Enter to 
   initiate a download.

5. Answer the download prompts according to your system requirements.  
   The file will be downloaded to the directory specified in your 
   communications software.

6. When the file transfer is complete and you are ready to leave the 
   BBS, type G (Goodbye) from the main menu.

******************
Upgrade your Modem
NOTE:  Your modem must be turned on for the following operation.

1. At the DOS prompt of the directory where your copy of the file has been 
   downloaded, type USRSDL and press Enter.  The zipped file will 
   self-extract several files onto your computer hard disk.

2. Type SDL and press Enter.
   The .EXE file checks the code embedded in itself.  If there is a problem, 
   an error message appears and the operation is terminated.  If you receive 
   an error message, download the file again. 

3. A screen appears with default COM port information.  

   If you want to alter the defaults, use the guidelines below.  
   
   /c=n    Enter this command to select one of four predefined COM ports 
           on an IBM-compatible PC.  Valid entries for n are 1, 2, 3, and 4.  
           The default is COM 2.  If you change the COM port setting, a 
           compatible IRQ will be displayed.
   
   /i=n    Enter this command to set up a custom port.  It specifies which 
           IRQ (interrupt request) the COM port will use to interrupt the 
           processor for service.  Valid entries for n are 2, 3, 4, 5, and 7.  
           The default is IRQ 3.
   
   /a=n    Enter this command to specify a port address, where n is the 
           hexadecimal address of a custom port only.
   
   /b=n    Enter this command to specify the bit rate at which the COM 
           port will communicate with the modem.  Valid entries for n are 
           9600, 19200, 38400, 57600, and 115200.  The default is 57600 bps.
   
   /q      This command allows you to shut off most of the screen display 
           as the program upgrades your modem code for batch-mode execution.  
           You will not be prompted to accept settings.
   
   /?      This command displays a help screen.

4. A prompt asks if you want to "Download Using These Settings? (Y/N)."  
   Type Y if you want to continue.  Type N if you want to abort the 
   operation.

   NOTE:  This is the only opportunity you will have to abort the operation.

5. Once you have accepted the settings, the software download will begin.  
   During this operation, the Modem Ready (MR) LED goes out.  

6. When the operation has successfully completed, the "Modem reports 
   download successful" message displays and the MR LED lights up again.

***************
Troubleshooting
If your modem indicates an error, try running the SDL program at a lower 
serial port rate.  If your computer doesn’t have a 16550 UART, a slower 
serial port rate can make all the difference.

You can also try running the program on a different PC.  An idiosyncracy 
of an off-brand PC or an uncommon version of DOS my hang up the SDL program.



Appendix J--Glossary



Adaptive Speed Leveling (ASL)
   Courier V.32 bis and V.32 terbo modems detect improved line conditions 
   and shift upward again to the next higher speed.  The modems at both 
   ends of the connection adapt independently, each detecting and adjusting 
   to line conditions.  ASL keeps the modems online, always operating at 
   the highest possible speed, and constantly ensuring data integrity.

Analog Loopback
   A modem self-test in which data from the keyboard is sent to the modem's 
   transmitter, modulated into analog form, looped back to the receiver, 
   demodulated into digital form, and returned to the screen for 
   verification.  

Analog Signals
   Continuous, varying waveforms such as the voice tones carried over 
   phone lines.  Contrast with digital signals.

Answer Mode
   A state in which the modem transmits at the predefined high frequency of 
   the communications channel and receives at the low frequency.  The 
   transmit/receive frequencies are the reverse of the calling modem 
   which is in Originate mode.

Application (application program)
   A computer program designed to perform a specific function, such as 
   a word processor or a spreadsheet.

ARQ
   Automatic Repeat Request.  A general term for error control protocols 
   which feature error detection and automatic retransmission of defective 
   blocks of data.  See HST, MNP, and V.42.

ASCII
   American Standard Code for Information Interchange.  A 7-bit binary code 
   (0's, 1's) used to represent letters, numbers, and special characters 
   such as $, !, and /.  Supported by almost every computer and terminal 
   manufacturer.  

Asymmetrical Modulation
   A duplex transmission technique which splits the communications channel 
   into one high speed channel and one slower channel.  During a call under 
   asymmetrical modulation, the modem with the greatest amount of data to 
   transmit is allocated the high speed channel.  The modem with less data 
   is allocated the slow, or back channel (450 bps).  The modems dynamically 
   reverse the channels during a call if the volume of data transfer changes.  

Asynchronous Transmission
   Data transmission in which the length of time between transmitted 
   characters may vary.  
   
   Because the time lapses between transmitted characters are not uniform, 
   the receiving modem must be signaled as to when the data bits of a 
   character begin and when they end.  The addition of Start and Stop bits 
   to each character serves this purpose.

Auto Answer 
   A feature in modems enabling them to answer incoming calls over the phone 
   lines without the use of a telephone receiver.

Auto Dial
   A feature in modems enabling them to dial phone numbers over the phone 
   system without the use of a telephone transmitter.

Baud Rate
   The number of discrete signal events per second occurring on a 
   communications channel.  Although not technically accurate, baud rate is commonly used to mean bit rate.

Binary Digit
   A 0 or 1, reflecting the use of a binary numbering system (only two 
   digits).  Used because the computer recognizes either of two states, 
   OFF or ON.  Shortened form of binary digit is bit.  

Bisync
   Binary Synchronous Control.  An earlier protocol developed by IBM for 
   software applications and communicating devices operating in synchronous 
   environments.  The protocol defines operations at the link level of 
   communications, for example, the format of data frames exchanged between 
   modems over a phone line.  See Protocol, HDLC, SDLC.

Bit Rate
   The number of binary digits, or bits, transmitted per second (bps). 
   Communications channels using telephone channel modems are established 
   at set bit rates, commonly 300, 1200, 2400, 4800, 9600, and 14400.

BPS
   The bits (binary digits) per second rate.

Buffer
   A memory area used as temporary storage during input and output 
   operations.  An example is the modem's command buffer.   Another is the 
   Transmit Data flow control buffer used for flow control and to store 
   copies of transmitted frames until they are positively acknowledged by 
   the receiving modem.

Byte
   A group of binary digits stored and operated upon as a unit.  A byte may 
   have a coded value equal to a character in the ASCII code (letters, 
   numbers), or have some other value meaningful to the computer.  In 
   user documentation, the term usually refers to 8-bit units or characters.  
   1 kilobyte (K) is equal to 1,024 bytes or characters; 64K indicates 
   65,536 bytes or characters. 

Call Indicate
   A call originating tone defined by ITU-T recommendation V.8.

Carrier
   A continuous frequency capable of being either modulated or impressed 
   with another information-carrying signal.  Carriers are  generated and 
   maintained by modems via the transmission lines of the telephone 
   companies.  

CCITT
   Formerly, an international organization that defined standards for 
   telegraphic and telephone equipment.  It has been incorporated into 
   its parent organization, International Telecommunication Union (ITU).  
   Telecommunication standards are now covered under Telecommunications 
   Standards Sector (TSS).  ITU-T replaces CCITT.  For example, the 
   Bell 212A standard for 1200 bps communication in North America was 
   referred to as CCITT V.22.  It is now referred to as ITU-T V.22.

Character
   A representation, coded in binary digits, of a letter, number, or other 
   symbol.  

Characters Per Second
   A data transfer rate generally estimated from the bit rate and the 
   character length.  
   
   For example, at 2400 bps, 8-bit characters with Start and Stop bits 
   (for a total of ten bits per character) will be transmitted at a rate 
   of approximately 240 characters per second (cps).  Some protocols, 
   such as USR-HST and MNP, employ advanced techniques such as longer 
   transmission frames and data compression to increase cps.

Class 1/EIA-578
   An American standard used between facsimile application programs and 
   facsimile modems for sending and receiving Class 1 faxes.

Class 2.0/EIA-592
   An American standard used between facsimile application programs and 
   facsimile modems for sending and receiving Class 2.0 faxes.

Cyclic Redundancy Checking (CRC)
   An error-detection technique consisting of a cyclic algorithm performed 
   on each block or frame of data by both sending and receiving modems.  
   The sending modem inserts the results of its computation in each data 
   block in the form of a CRC code.  The receiving modem compares its 
   results with the received CRC code and responds with either a positive 
   or negative acknowledgment.  In the ARQ protocol implemented in U.S. 
   Robotics high speed modems, the receiving modem accepts no more data 
   until a defective block is received correctly.

Data Communications
   A type of communications in which computers and terminals are able to 
   exchange data over an electronic medium.  

Data Compression
   When the transmitting modem detects redundant units of data, it recodes 
   them into shorter units of fewer bits.  The receiving modem then 
   decompresses the redundant data units before passing them to the 
   receiving computer.

Data Compression Table
   A table of values assigned for each character during a call under data 
   compression.  Default values in the table are continually altered and 
   built during each call:  the longer the table, the more efficient 
   throughput gained.

   If a destructive Break is sent during a call (see the &Y command), 
   causing the modems to reset the compression tables, you can expect 
   diminished throughput.

Data Mode
   The mode in which the fax modem is capable of sending and receiving 
   data files.  A standard modem without fax capabilities is always in 
   Data mode.

DCE
   Data Communication (or Circuit-Terminating) Equipment.  In this manual, 
   the term applies to dial-up modems that establish and control the data 
   link via the telephone network.

Dedicated Line
   A user-installed telephone line used to connect a specified number of 
   computers or terminals within a limited area, for example, one building.  
   The line is a cable rather than a public-access telephone line.  The 
   communications channel may also be referred to as nonswitched because 
   calls do not go through telephone company switching equipment.

Default
   Any setting assumed, at startup or reset, by the computer's software 
   and attached devices, and operational until changed by the user.  

Digital Loopback
   A test that checks the modem's RS-232 interface and the cable that 
   connects the terminal or computer and the modem.  The modem receives 
   data (in the form of digital signals) from the computer or terminal, 
   and immediately returns the data to the screen for verification.

Digital Signals
   Discrete, uniform signals.  In this manual, the term refers to the 
   binary digits 0 and 1. 

Duplex
   Indicates a communications channel capable of carrying signals in both 
   directions. See Half Duplex, Full Duplex.

EIA
   Electronic Industries Association, which defines electronic standards in 
   the U.S. 

Equalization
   A compensation circuit designed into modems to counteract certain 
   distortions introduced by the telephone channel.  Two types are used:  
   fixed (compromise) equalizers and those that adapt to channel conditions.  
   U.S. Robotics high speed modems use adaptive equalization.

Error Control 
   Various techniques which check the reliability of characters (parity) or 
   blocks of data.  V.42, MNP and HST error control protocols use error 
   detection (CRC) and retransmission of errored frames (ARQ). 

Facsimile
   A method for transmitting the image on a printed page from one point to 
   another.  Commonly referred to as Fax.

Fax Mode
   The mode in which the fax modem is capable of sending and receiving files 
   in a facsimile format.  

Flash ROM
   Read Only Memory that can be erased and reprogrammed. 

Flow Control
   A mechanism that compensates for differences in the flow of data input 
   to and output from a modem or other device. 

Frame
   A data communications term for a block of data with header and trailer 
   information attached.  The added information usually includes a frame 
   number, block size data, error-check codes, and Start/End indicators.

Full Duplex
   Signal flow in both directions at the same time.  In microcomputer 
   communications, may refer to the suppression of the online Local Echo.  

Half Duplex
   Signal flow in both directions, but only one way at a time.  In 
   microcomputer communications, may refer to activation of the online 
   Local Echo, which causes the modem to send a copy of the  transmitted 
   data to the screen of the sending computer.

HDLC
   High Level Data Link Control.  A standard protocol developed by the 
   International Standards Organization for software applications and 
   communicating devices operating in synchronous environments.  The 
   protocol defines operations at the link level of communications, 
   for example, the format of data frames exchanged between modems over 
   a phone line.  See Bisync, Protocol, SDLC.

HST
   High Speed Technology, U.S. Robotics' proprietary signaling scheme, 
   design and error control protocol for high-speed modems.  HST 
   incorporates trellis-coded modulation, for greater immunity from 
   variable phone line conditions, and asymmetrical modulation for more 
   efficient use of the phone channel at speeds of 4800 bps and above.  HST 
   also incorporates MNP-compatible error control procedures adapted to 
   asymmetrical modulation.

Hz
   Hertz, a frequency measurement unit used internationally to indicate 
   one cycle per second.

ITU-T
   International Telecommunication Union-Telecommunication sector.  
   Formerly referred to as CCITT.  An international organization that 
   defines standards for telegraphic and telephone equipment.  For example, 
   the Bell 212A standard for 1200 bps communication in North America is 
   observed internationally as ITU-T V.22.  For 2400 bps communication, 
   most U.S. manufacturers observe V.22 bis.

LAPM 
   Link Access Procedure for Modems, an error control protocol incorporated 
   in ITU-T Recommendation V.42.  Like the MNP and HST protocols, LAPM 
   uses cyclic redundancy checking (CRC) and retransmission of corrupted 
   data (ARQ) to ensure data reliability.

Local Echo
   A modem feature that enables the modem to send copies of keyboard 
   commands and transmitted data to the screen.  When the modem is in 
   Command mode (not online to another system) the local echo is invoked 
   through the ATE1 command.  The command causes the modem to display your 
   typed commands.  When the modem is online to another system, the local 
   echo is invoked through the ATF0 command.  This command causes the 
   modem to display the data it transmits to the remote system.

MI/MIC
   Mode Indicate/Mode Indicate Common, also called Forced or Manual 
   Originate.  Provided for installations where other equipment, rather 
   than the modem, does the dialing.  In such installations, the modem 
   operates in Dumb mode (no Auto Dial capability), yet must go off 
   hook in Originate mode to connect with answering modems.  See MI/MIC 
   Closure in Appendix G.

MNP
   Microcom Networking Protocol, an asynchronous error control protocol 
   developed by Microcom, Inc. and now in the public domain.  The protocol 
   ensures error-free transmission through error detection (CRC) and 
   retransmission of errored frames.  U.S. Robotics modems use MNP 
   Levels 1-4 and Level 5 data compression.  MNP Levels 1-4 have been 
   incorporated into ITU-T Recommendation V.42.  Compare HST.

Modem
   A device that transmits/receives computer data through a communications 
   channel such as radio or telephone lines.  The Courier is a telephone 
   channel modem that modulates, or transforms, digital signals from a 
   computer into the analog form that can be carried successfully on a 
   phone line.  It also demodulates signals received from the phone line 
   back to digital signals before passing them to the receiving computer.  

Nonvolatile Memory (NVRAM)
   User-programmable random access memory whose data is retained when 
   modem power is turned off.  Used in Courier modems to store a 
   user-defined default configuration loaded into random access memory 
   (RAM) at power on.

OFF/ON Hook
   Modem operations which are the equivalent of manually lifting a 
   phone receiver (taking it off hook) and replacing it (going on hook).
   
Online Fallback
   A feature that allows high speed error-control modems to monitor line 
   quality and fall back to the next lower speed if line quality degrades.  
   The modems fall forward as line quality improves.

Originate Mode
   A state in which the modem transmits at the predefined low frequency 
   of the communications channel and receives at the high frequency.  The 
   transmit/receive frequencies are the reverse of the called modem which 
   is in Answer mode.  

Parallel Transmission
   The transfer of data characters using parallel electrical paths for 
   each bit of the character, for example, 8 paths for 8-bit characters.  
   Data is stored in computers in parallel form, but may be converted to 
   serial form for certain operations.  See Serial Transmission.

Parity
   An error-detection method that checks the validity of a transmitted 
   character.  Character checking has been surpassed by more reliable 
   and efficient forms of block-checking, including Xmodem-type protocols 
   and the ARQ protocol implemented in Courier modems. 
   
   The same type of parity must be used by two communicating computers, 
   or both may omit parity.  When parity is used, a parity bit is added 
   to each transmitted character.  The bit's value is 0 or 1, to make the 
   total number of 1's in the character even or odd, depending on which 
   type of parity is used.

Protocol
   A system of rules and procedures governing communications between two 
   or more devices.  Protocols vary, but communicating devices  must 
   follow the same protocol in order to exchange data.  The format of 
   the data, readiness to receive or send, error detection and error 
   correction are some of the operations that may be defined in protocols.  
   
RAM
   Random Access Memory.  Memory that is available for use when the modem 
   is turned on, but that clears of all information when the power is 
   turned off.  The modem's RAM holds the current operational settings, 
   a flow control buffer, and a command buffer. 

Remote Access
   A feature that allows a remotely-located user to view the Courier's 
   configuration screens and change the Courier's configuration.  Password 
   protection is available.

Remote Digital Loopback
   A test that checks the phone link and a remote modem's transmitter and 
   receiver.  Data entered from the keyboard is transmitted from the 
   initiating modem, received by the remote modem's receiver, looped 
   through its transmitter, and returned to the local screen for 
   verification.

Remote Echo
   A copy of the data received by the remote system, returned to the 
   sending system and displayed on the screen.  Remote echoing is a 
   function of the remote system.

ROM
   Read Only Memory.  Permanent memory, not user-programmable.  The 
   Courier's factory settings are stored in ROM and can be read (loaded) 
   into RAM as an operational configuration if DIP switch S10 is ON at 
   power on.

Serial Transmission
   The transfer of data characters one bit at a time, sequentially, using 
   a single electrical path.  See Parallel Transmission.

Start/Stop Bits
   The signaling bits attached to a character before the character is 
   transmitted during Asynchronous Transmission.

SDLC
   Synchronous Data Link Control.  A protocol developed by IBM for software 
   applications and communicating devices operating in IBM's Systems 
   Network Architecture (SNA).  The protocol defines operations at the 
   link level of communications, for example, the format of data frames 
   exchanged between modems over a phone line.  See Bisync, Protocol, HDLC.
   
Synchronous Transmission
   A form of transmission in which blocks of data are sent at strictly 
   timed intervals.  Because the timing is uniform, no Start or Stop 
   bits are required.  Compare Asynchronous Transmission.

   Some mainframes only support synchronous communications unless their 
   owners have installed a synchronous adapter and appropriate software.

Terminal
   A device whose keyboard and display are used for sending and receiving 
   data over a communications link.  Differs from a microcomputer in that 
   it has no internal processing capabilities.  Used to enter data into 
   or retrieve processed data from a system or network. 

Terminal Mode
   An operational mode required for microcomputers to transmit data.  In 
   Terminal mode the computer acts as if it were a standard terminal such 
   as a teletypewriter, rather than a data processor.  Keyboard entries 
   go directly to the modem, whether the entry is a modem command or data 
   to be transmitted over the phone lines.  Received data is output 
   directly to the screen.  The more popular communications software 
   products control Terminal mode as well as enable more complex 
   operations, including file transmission and saving received files.

Throughput
   The amount of actual user data transmitted per second without the 
   overhead of protocol information such as Start and Stop bits or frame 
   headers and trailers.  Compare characters per second.

Transmission Rate
   Same as Bit Rate.

V.17
   An ITU-T standard for facsimile operations that specifies modulation 
   at 14.4K bps, with fallback to 12K bps.

V.21--Fax
   An ITU-T standard for facsimile operations at 300 bps.  U.S. Robotics 
   or compatible fax devices then transmit or receive at higher speeds. 

V.21--Modem
   An ITU-T standard for modem communications at 300 bps.  Modems made in 
   the U.S. or Canada follow the Bell 103 standard.  However, the modem 
   can be set to answer V.21 calls from overseas.

V.22
   A ITU-T standard for modem communications at 1200 bps, compatible with 
   the Bell 212A standard observed in the U.S. and Canada.

V.22 bis        
   An ITU-T standard for modem communications at 2400 bps.  The standard 
   includes an automatic link negotiation fallback to 1200 bps and 
   compatibility with Bell 212A/V.22 modems.

V.23
   An ITU-T standard for modem communications at 1200 bps with a 75 bps 
   back channel.  Used in the U.K.

V.25
   An ITU-T standard for modem communications.  Among other things, V.25 
   specifies an answer tone different from the Bell answer tone.  All U.S. 
   Robotics modems can be set with the B0 command so that they use the 
   V.25 2100 Hz tone when answering overseas calls.

V.25 bis
   An ITU-T standard for synchronous communications between the mainframe 
   or host and the modem using the HDLC or character-oriented protocol.  
   Modulation depends on the serial port rate and setting of the 
   transmitting clock source, &X.

V.27 ter
   An ITU-T standard for facsimile operations that specifies modulation 
   at 4800 bps, with fallback to 2400 bps.

V.29
   An ITU-T standard for facsimile operations that specifies modulation 
   at 9600 bps, with fallback to 7200 bps.

V.32
   An ITU-T standard for modem communications at 9600 bps and 4800 bps.  
   V.32 modems fall back to 4800 bps when line quality is impaired, and 
   fall forward again to 9600 bps when line quality improves.

V.32 bis
   An ITU-T standard that extends the V.32 connection range:  4800, 7200, 
   9600, 12K and 14.4K bps.  V.32 bis modems fall back to the next lower 
   speed when line quality is impaired, and fall back further as necessary.  
   They fall forward to the next higher speed when line quality improves.  

V.32 terbo
   Modulation scheme that extends the V.32 connection range:  4800, 7200, 
   9600, 12K,  14.4K, 16.8K, 19.2K, and 21.6K bps.  V.32 terbo modems fall 
   back to the next lower speed when line quality is impaired, and fall 
   back further as necessary.  They fall forward to the next higher speed 
   when line quality improves.  

V.34
   An ITU-T standard that allows data rates as high as 28.8K bps.  

V.42
   An ITU-T standard for modem communications that defines a two-stage 
   process of detection for LAPM error control.      

V.42 bis
   An extension of ITU-T V.42 that defines a specific data compression 
   scheme for use with V.42 error control.

V.8
   ITU-T recommendation that defines procedures for starting and ending 
   sessions of data transmission.

V.Fast Class (V.FC)
   Proprietary modulation scheme developed by Rockwell International for 
   data communication speeds up to 28.8K bps.

Word Length
   The number of bits in a data character without parity, start or stop 
   bits.

Xmodem
   The first of a family of error control software protocols used to 
   transfer files between modems.  These protocols are in the public 
   domain and are available from many bulletin board services.  

XON/XOFF
   Standard ASCII control characters used to tell an intelligent device 
   to stop/resume transmitting data.  In most systems typing <Ctrl>-S sends 
   the XOFF character.  Some devices, including the Courier, understand 
   <Ctrl>-Q as XON; others interpret the pressing of any key after 
   <Ctrl>-S as XON. 


Appendix K--Tecnical Specifications


Your modem uses multiple standard modulation protocols and is also 
compatible with many nonstandard schemes.

V.34
   28.8K, 26.4K, 24K, 21.6K, 19.2K, 16.8K, 14.4K, 12K, 9600, 7200, 
   4800, and 2400 bps asynchronous Trellis Coded Modulation (TCM)

V.Fast Class (V.FC)
   28.8K, 26.4K, 24K, 21.6K, 19.2K, 16.8K, 14.4K bps asynchronous 
   Trellis Coded Modulation (TCM)

U.S. Robotics V.32 terbo 
   21.6K, 19.2K, 16.8K, 14.4K. 12K, 9600, 7200 bps asynchronous, 19.2K, 
   16.8K, 14.4K. 12K, 9600, 7200 bps synchronous, Trellis Coded 
   Modulation (TCM)

   4800 bps, synchronous/asynchronous, Quadrature Amplitude Modulation 
   (QAM) 

U.S. Robotics High Speed Technology (HST)
   16.8K, 14.4K, 12K, 9600, 7200 bps, asynchronous, 
   asymmetrical, 450 bps back channel with automatic handshake 
   adjustment to 300 bps, Trellis Coded Modulation (TCM), Quadrature 
   Amplitude Modulation (QAM) 

   4800 bps, asynchronous, asymmetrical, 450 bps back 
   channel with automatic handshake adjustment to 300 bps, Quadrature 
   Amplitude Modulation (QAM)

ITU-T V.32 bis
   14.4K. 12K, 9600, 7200 bps, synchronous/asynchronous, Trellis Coded 
   Modulation (TCM)

   4800 bps, synchronous/asynchronous, Quadrature Amplitude Modulation 
   (QAM) 

Additional Compatibility Features
   ITU-T V.32, 9600 bps, synchronous, asynchronous, Trellis Coded Modulation 
   (TCM); 4800 bps, synchronous, asynchronous, Quadrature Amplitude 
   Modulation (QAM)

   ITU-T V.25 2100 Hz tone

   ITU-T V.23, 1200 bps, asymmetrical (1200/75 bps), Frequency Shift 
   Keying (FSK)

   ITU-T V.22 bis, 2400 bps, synchronous/asynchronous, Quadrature Amplitude 
   Modulation (QAM) 

   ITU-T V.22, 1200 bps, synchronous/asynchronous, Differential Phase 
   Shift Keying (DPSK)

   Bell 212A, 1200 bps, synchronous/asynchronous, Differential Phase 
   Shift Keying (DPSK)

   Bell 103, 300 bps, asynchronous, Frequency Shift Keying (FSK)

   ITU-T V.21, 300 bps, asynchronous, Frequency Shift Keying (FSK)

Error Control Standards
   ITU-T V.42 error control protocol at 14.4K, 12K, 9600, 7200, 4800 bps 
   (V.32 bis mode) and at 2400/1200 bps

   U.S. Robotics HST error control protocol, asymmetrical mode, at 16.8K, 
   14.4K, 12K, 9600, 7200, 4800 bps, 450/300 bps back channel

   Microcom Networking Protocol (MNP) error control protocol, Levels 2-4 
   at 14.4K, 12K, 9600, 7200, 4800 bps (V.32 bis mode) and at 2400/1200 bps
   
Data Compression Protocols
   ITU-T V.42 bis data compression (all modes and speeds of 1200 bps and 
   higher)                   
   Microcom Networking Protocol (MNP) Level 5 data compression (all modes 
   and speeds of 1200 bps and higher)

Fax Standards
   The Courier modem provides Group III-compatibility when combined with 
   Class 1 or Class 2.0 fax software.  In addition, the modem adheres to 
   the following standards.

   TIA/EIA-578       Service Class 1 Asynchronous Facsimile DCE Control 
		     Standard

   TIA/EIA-592       Service Class 2.0 Asynchronous Facsimile 
		     DCE Control Standard

   ITU-T V.17        14.4K/12K bps

   ITU-T V.29        9600/7200 bps

   ITU-T V.27 ter    4800/2400 bps

   ITU-T V.21        300 bps


Serial Port Rates
   115.2K, 57.6K, 38.4K, 19.2K, 9600, 4800, 2400, 1200, 300 bps

Adaptive Speed Leveling
   21.6K, 19.2K, 16.8K, 14.4K, 12K, 9600, 7200, 4800 bps

Phone Line Interface
   RJ11 phone jacks

Communications Channel
   Full/half duplex on 2-wire dial-up, dedicated, or leased phone lines; 
   demand-driven high speed channel turnaround in HST mode; symmetrical 
   speeds in V.32 bis mode

Operational Modes
   Synchronous/Asynchronous, Auto Dial/Answer, Manual Originate/Answer, 
   Smart/Dumb mode, Auto Dial/Auto Answer, Auto Answer only, Forced 
   Originate (MI/MIC)

   Fax Modems:  The above modes plus fax mode


Dialing
   Dialing Rotary (pulse 0-9), Tone (DTMF 0-9, #, *), a-z when in Quote 
   (") Mode

Data Format
   Binary, serial; defaults to 8-bit word length, no parity, and 1 stop bit

	Word      Parity         Stop
	Length    (1 Bit)        Bits

	7         Even, Odd       1
		  Mark, Space
	7         None            2
	8         None            1

Front Panel status lights 
   HS      High Speed (above 2400 bps)
   AA      Auto Answer/Answer
   CD      Carrier Detect
   OH      Off Hook
   RD      Received Data
   SD      Send Data
   TR      Terminal Ready (DTR)
   MR      Modem Ready/Test mode
   RS      Request to Send
   CS      Clear to Send
   SYN     Synchronous mode
   ARQ/    Error control connection established
   FAX     Modem in Fax mode

Flow Control Buffers
   Transmit Buffer
	Error control:  3.25k bytes
	Non-Error control:  1.5k bytes, 128-byte option
   
   Receive Buffer:  2K bytes

Command Buffer
   60 characters, exclusive of AT prefix, Carriage Return and spaces

Test Options
   Analog loopback with test pattern
   Remote digital loopback
   Digital loopback
   Test pattern
   Dial test

Call Progress Codes
   FAX
   DATA
   NO DIAL TONE
   BUSY
   NO ANSWER
   RINGING
   VOICE

Failed Call Timeout
   60-sec. default, programmable 2-255 sec.

Answer Tone Timeout
   60 sec.

Fax Service Class 1 Commands
   +FCLASS=n (0,1) Class identification and control
   +FTS=n (0,255)  Stop transmission and pause, 10ms.
   +FRS=n (0,255)  Wait for silence, 10 ms.
   +FTM=n (3,24,48,72,73,74,96,121,122,145,146)
	  Transmit data with carrier
   +FRM=n (3,24,48,72,73,74,96,121,122,145,146)
	  Receive data with carrier
   +FTH=n (3,24,48,72,73,74,96,121,122,145,146)
	  Transmit HDLC data with carrier
   +FRH=n (3,24,48,72,73,74,96,121,122,145,146)
	  Receive HDLC data with carrier           

FAX service class 2.0 commands
   Class 2.0 fax commands are too numerous to be listed here.  For 
   information on Class 2.0 technical specifications, contact Global 
   Engineering Documents, at 1-800-854-7179.  The document that covers 
   this information is:

      ANSI/EIA/TIA-592-1993 (EIA-592)
      Asynchronous Facsimile DCE Control Standard
      May, 1993

Optional Class 2.0 FAX commands supported
   U.S. Robotics implements the following optional Class 2.0 fax commands:
   +FNS=0,1          Pass-through non-Standard negotiation byte string 
   +FCR=0,1          Capability to receive 
   +FAA=0,1          Adaptive Answer mode 
   +FCT=0-255 sec.   Phase C Timeout 
   +FHS=0-255        Hangup Status Code, read only
   +FMS=0-3          Minimum Phase C Speed 
   +FBS?=500,100     Buffer size, read only 

V.25 bis Synchronous Commands and Result Codes 
   Commands:  Connect incoming call (CIC); Call request using number 
   provided (CRN); Call Request with memory location (CRS); Disregard 
   incoming call (DIC); Program number (PRNn); Request list of forbidden 
   numbers (RFN); Request list of stored numbers (RLN). 

   Dial options: 0-9 & : > < = P T); 

   Result Codes:  Call failure indication (CFI) with optional parameters:  
   Abort call (CFAB); local modem busy (CFCB); Engaged tone (CFET); 
   Forbidden call (CFFC); Number not stored (CFNS); Answer tone not 
   detected (CFNT); Ring tone (CFRT); Connect (CNX); List of numbers 
   (LS); List of forbidden numbers (LSF); List of stored numbers (LSN); 
   Incoming call (INC); Invalid (INV) with optional parameters:  Message 
   syntax error (INVMS); Command Unknown (INVCU); Parameter syntax error 
   (INVPS); Parameter value error (INVPV); Valid (VAL). 

   Commands and Result Codes not supported:  Call request with 
   identification number (CRI); Program identifier (PRI); Request list of 
   identification numbers (RLI); List of delayed call numbers (RLD).

Answer Tone Detector
   2200-2300 Hz

Loss of Carrier (Disconnect Timer) 
   0.7-sec. default, programmable 0.2-25.5 sec.

Equalization
   Adaptive

Transmitter Carrier Frequencies
   V.34
	Originate Mode: 1800 Hz
	Answer Mode:    1800 Hz

	Originate Mode: 1829 Hz
	Answer Mode:    1829 Hz

	Originate Mode: 1867 Hz
	Answer Mode:    1867 Hz

	Originate Mode: 1920 Hz
	Answer Mode:    1920 Hz

	Originate Mode: 1959 Hz
	Answer Mode:    1959 Hz

	Originate Mode: 2000 Hz
	Answer Mode:    2000 Hz

   V.Fast Class
	Originate Mode: 1800 Hz
	Answer Mode:    1800 Hz

	Originate Mode: 1875 Hz
	Answer Mode:    1875 Hz

	Originate Mode: 1920 Hz
	Answer Mode:    1920 Hz

   USR-V.32 terbo/V.32 bis/V.32
	Originate Mode: 1800 Hz
	Answer Mode:    1800 Hz

   USR-HST, 450 bps back channel
	Originate Mode: 375 Hz
	Answer Mode:    1800 Hz

   USR-HST, 300 bps back channel
	Originate Mode: 350 Hz
	Answer Mode:    1800 Hz

   V.23
	Originate Mode: 
	Mark:   390 Hz
	Space:  450 Hz
	Answer Mode:
	Mark:   1300 Hz
	Space:  2100 Hz

   V.22 bis, V.22, Bell 212A
	Originate Mode: 1200 Hz
	Answer Mode:    2400 Hz

   Bell 103
	Originate Mode: 
	Mark:   1270 Hz
	Space:  1070 Hz
	Answer Mode:
	Mark:   2225 Hz
	Space:  2025 Hz

   V.21
	Originate Mode:
	Mark:   980 Hz
	Space:  1180 Hz
	Answer Mode:    
	Mark:   1650 Hz
	Space:  1850 Hz


Receiver Carrier Frequencies
   V.34
	Originate Mode: 1800 Hz
	Answer Mode:    1800 Hz

	Originate Mode: 1829 Hz
	Answer Mode:    1829 Hz

	Originate Mode: 1867 Hz
	Answer Mode:    1867 Hz

	Originate Mode: 1920 Hz
	Answer Mode:    1920 Hz

	Originate Mode: 1959 Hz
	Answer Mode:    1959 Hz

	Originate Mode: 2000 Hz
	Answer Mode:    2000 Hz

   V.Fast Class
	Originate Mode: 1800 Hz
	Answer Mode:    1800 Hz

	Originate Mode: 1875 Hz
	Answer Mode:    1875 Hz

	Originate Mode: 1920 Hz
	Answer Mode:    1920 Hz

   USR-V.32 terbo/V.32 bis/V.32
	Originate Mode: 1800 Hz
	Answer Mode:    1800 Hz

   USR-V.32 terbo/V.32 bis/V.32
	Originate Mode: 1800 Hz
	Answer Mode:    1800 Hz

   USR-HST, 450 bps back channel
	Originate Mode: 1800 Hz
	Answer Mode:    375 Hz

   USR-HST, 300 bps back channel
	Originate Mode: 1800 Hz
	Answer Mode:    350 Hz

   V.23
	Originate Mode: 
	Mark:   1300 Hz
	Space:  2100 Hz
	Answer Mode:
	Mark:   390 Hz
	Space:  450 Hz

	V.22 bis, V.22, Bell 212A
	Originate Mode: 2400 Hz
	Answer Mode:    1200 Hz

   Bell 103
	Originate Mode: 
	Mark:   2225 Hz
	Space:  2025 Hz
	Answer Mode:
	Mark:   1270 Hz
	Space:  1070 Hz

   V.21
	Originate Mode:
	Mark:   1650 Hz
	Space:  1850 Hz
	Answer Mode:
	Mark:   980 Hz
	Space:  1180 Hz


Receive Sensitivity 
   - 44 dBm + 2 dBm

Transmit Level 
   - 9 dBm maximum

Transmitter Frequency Tolerance
   .01%

Certification
   FCC Part 68 and Part 15, Class B Domestic; IC (Canada), UL listed

Power Consumption
   5 watts

Size
   6.375 x 10.3 x 1.337 inches

