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 Hello, and welcome to the first in a continuing series on the ESS1 and 1A 
switching systems.  The information in this series had been obtained from my
knowledge and by trashing various empire (AT&T,BELL) trash binns.

In this first file I will start off with a very basic review of what the
ESS system is, and will then go on to talk about some other things you
will find interesting.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-



The ESS System In Review
------------------------

ESS (Which stands for Electronic Switching System) was designed by good old AT&T
in the state of the art labs of the computer-controlled space-division.  The
principle is simple, you have a switching system that is controlled by simple
electronics and stored computer programs. (not to be confused with CCIS which is
just a interoffice command link).

The ESS system is a class 5(End Office) system, and has some spinoffs (like the 
No. 10A RSS [Remote Switching System]).  It uses digital transmissions, although
they must be converted to analog by a hybrid as this is what kind of electronics
AT&T chose to use.

The ESS is divided in to seperate modules, so as to make repairs and additions
easier.  Each module is connected to the system by interfaces (one of which will
be covered later).  In a whole, the ESS system provides the standard BORSCHT
functions, plus some extra ones.

Well, them there's the basics, now on with the good, technical, informational, 
fun stuff.........

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-




 ESS1A Procesor
 --------------

  The follwing is about the 1A Processor, and will give you an understanding on 
how it functions.

  The 1A processor is used for a number of ESS systems, but most specifically is 
used for the following:
 
 o   To control the 4 ESS switch.

 o   To control the 1A ESS switch.

 o   To be added to older 1 ESS switches, so as to update it to a 1A ESS.

 o   To support future switching systems.

 o   To accommodate bulk memory systems.

 o   And to provide real time and continuous control through highly automatic
     maintenance. (less than 2 hours downtime in 40 years continuous operation).

 The 1A processor uses stored programs, and operates in a real time environment.
The processor can function without being hooked up to the switching network.
The processor is devoted to internal maintenance and administrative tasks.  So
TELCO employe's can monitor the processor (from now on called the 1A) it is 
hooked up to control panels and to I/O terminals.  (which, incidentally 
interface with software defined I/O channels).

 All frames (they make up the 1A) sent out from the 1A are duplicated.
So that a failure from one won't screw up and equipment.

 The following is a high level block diagram of the 1A:

 _________
|Attached |
|Processor|_________
|System   |        |
 ---------         |
                   |
                   |                                      ___________
 ___________       |                                     |           |
|           |      ^                                     | Auxiliary |
| File Store|----< <-------------------*-----------------| Data      |
|           |                          |                 | System    |
 -----------                           |                 |           |
                                       |                  -----------
                                       |
                                       |
                                       | AU BUS 
                                       |
                                       |
 ___________                 __________|_________               ____________
|           |               |                    |             |            |
| Program   |   PS Bus      |      Central       |   CS Bus    | Call Store |
| Store     |---------------|      Control       |-------------|            |
|           |               |                    |              ------------
 -----------                 ----------|---------              
                                       |
                                       | PU Bus      ___________   Data and
                                       |            |           |  control
                                       *------------|  I/O      |-------------
                                       |            | Interface |       to/from
                                       |            |           |         I/O 
                                       |             -----------       terminals
                                       |                  |           
                                       |                  |
                                       |                  |E2A Telemetry
                                       | PU Bus           |Control
                                       |                  |
               Status                  |                  |
 _________     And             ________|_______           |
|         |    Control        |                |<----------    Pu Bus    To/From
| Control |-------------------| Periphel       |--------------------------using
| Panels  |                   | System         |                         system
|         |                   | Interface      |                        peripheal
 ---------                    |                |                              
                              |                |  E2A Telemetry Control Inhibit
to No. 2    Telemetry Data    |                |<----------------------\
SCCS        And Control       |                |                        | From
Maintenance-------------------|                |<--Office--Alarms-------|Using
Facility                      |                |                        |System
                              |                |<--Building--Alarms----/
                              |                |
                               ----------------

         LEGEND
         ------
  AU--Auxiliary Unit
  CS--Call Store
  PS--Program Store
  PU--Peripheral Unit
SCCS--Switching Control Center System

About the above:

Central Control: Interfaces with the 1A, and performs the processing functions
     of the 1A.  It also executes all maintenance routines.

Program Store: High speed semiconductor that stores program instructions, and 
     system configuration system.

Call Store: Similar to the above, but is used for storage translation data, and
     frequently changed call processing data, such as:
 
       o  Status of trunks and switching network.

       o  Records of network terminations used for each call in progress.

       o  Digits received and digits to be outpulsed.

       o  Maintenance data related to programmed diagnostic tests.

     Call store also includes an emergency system recovery program, used to 
     establish a working system of a program store failure.

File Store:  Magnetic disk memory, used for program backup.

Attached Processor System: 3B20D computer, of which one or more are used as 
      slave processors (used for multitasking, ect.)

Auxillary Data System:  Magnetic tape system used to store and retrieve data
      such as system reinitialization, memory dumps, ect......

I/O interface:  Used to connect 1A to terminals used to input control mesages,
      and to recieve status messages.

Peripheral System Interface:  Serves as the main junction between all peripherals.

Control Panels:  An additional I/O device used to monitor the 1A, and to 
      exercise manual control over the 1A.

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