                    SWITCHED DIGITAL SERVICE 56 (SDS 56)

DESCRIPTION
-------------
SDS 56 is a digital telecommunications service available from 
Pacific Bell.  

It is a low-cost digital, dial-up alternative to leased lines or 
analog services.

CAPABILITIES 
------------
 Switched 56 is easy to use -- you simply dial another user's 
Switched 56 number to transmit data at 56 Kilobits per second 
(Kbps).  And it's affordable -- your data call won't cost any more 
than a regular voice call.  For all of these reasons, Switched 56 is 
especially suited to intermittent, high-speed data transmission 
applications.

EASE OF USE:  A standard telephone number is provided for placing 
and receiving Switched 56 calls, including 1+, 7 and 10 digit 
intraLATA , interLATA and international dialing.

PRICING:  Pricing is similar to regular telephone service -- You pay 
only for what you use:  a low, flat monthly charge plus intraLATA 
transport at existing voice usage rates, with time-of-day discounts.

RELIABILITY:  Pacific Bell Switched 56 services are designed to 
exceed the minimum performance thresholds; they have a Bit Error 
Rate of 8.9 x 10(-8) and 95 percent Error Free Seconds (EFS) on 99 
percent of end-to-end intraLATA calls.

SUPPORT:  All of our data transport products and services are backed 
by extensive network services experience and highly trained 
professionals.  If your require assistance, call us 24 hours a day, 
and day of the year.


COMPATIBILITY
-----------------
To ensure the quality and reliability of Pacific Bell Switched 56, 
we've designed and engineered the Pacific Bell Circuit Switched Data 
56 (CSD 56) network exclusively for switched digital data services.

Pacific Bell offers three products which provide Switched 56 
capability using the CSD 56 network:  Centrex IS, CenPath, SDS IS 
and SDS 56.  These products connect to the CSD 56 network and are 
fully interoperable with all other connected services, including 
Switched 56 services from other local exchange carriers (LECs) and 
inter-exchange carriers (IECs).  As a result, Pacific Bell Switched 
56 users can complete local, long distance, interstate and even 
international calls.

You have a choice of IECs on demand.

WHAT YOU NEED
-----------------

You need special equipment to use Switched 56 services, which varies 
depending on the application.  In all cases you need a DSU (either a 
Datapath compatible two-wire DSU or a four-wire Switched 56 DSU with 
dialing capability.

Pacific Bell has arrangements with equipment manufacturers to help 
you select and install the correct equipment.

BUSINESS USES FOR SDS 56 and SWITCHED 56
-----------------------------------------------

VIDEO CONFERENCING:  This exciting application allows businesses to 
hold face-to-face, interactive meetings between people in two or 
more locations.   While the cost of data transport previously put 
video conferencing out of the reach of many companies, Switched 56 
services make it affordable.  Most video codecs (used for video 
conferencing) are designed to take two Switched 56 inputs and 
automatically combine them for 112 Kbps.

HIGH SPEED BULK DATA TRANSPORT:  Switched 56 offers the speed of 
dedicated services and the economy of dial-up for transferring data 
files.  Applications include uploading/downloading, terminal to host 
access, database access and shared library resources.

IMAGING:  With Switched 56, users can quickly exchange high quality 
images, replacing overnight courier services.  Imaging applications 
include advertising layouts, radiology images, real estate listings, 
digitized microfiche, electronic publishing and digitized 
fingerprints.

DISASTER RECOVERY/BACKUP:  If your are using a 56 Kbps Digital Data 
Service (DDS) or Advanced Digital Network (ADN) circuit, it makes 
sense to back it up with digital Switched 56 rather than a slower 
speed analog dial-up service.  That way, you can enjoy digital 
service and maintain productivity even during a disaster situation.

GROUP IV FAX:  Group IV fax offers superior resolution and is, at a 
minimum, five times faster than Group III fax (the current 
standard).  Switched 56 offers a flexible and low-cost method for 
connecting your Group IV machines together.  Group IV fax is great 
for blueprints, library documents, legal documents and detailed 
graphics.

HIGH SPEED TELECOMMUTING:  For telecommuters using high speed 
workstations, Switched 56 alleviates the communications bottleneck 
caused by modems and analog lines.

HIGH QUALITY DIGITIZED AUDIO (7.5 Khz):  Many radio stations are 
installing Switched 56 service to broadcast from remote locations 
instead of using satellite transmission or leased lines.

CONNECTING LANS:  SDS 56 can be a cost-effective way to link distant 
LANs.  With the right equipment, data destined for a remote LAN can 
be recognized and the line automatically dialed for a connection 
through SDS 56.

CONNECTING REMOTE USERS TO LANS:  SDS 56 can be a cost-effective way 
to connect remote users (PCs, Macintoshes and workstations) to their 
company LAN or host computer.

AVAILABILITY
----------------
Like our other Switched 56 products, SDS 56 transmits data at a 
full-duplex, digital synchronous 56 Kbps rate for the price of a 
voice phone call.  SDS 56 significantly increases Pacific Bell's 
Switched 56 availability to more than 80% of our business 
customers.  With SDS 56 technology, Pacific Bell can now offer 
Switched 56 service to customers who previously could not be served 
because of technical limitations.  In addition, SDS 56 provides a 
Switched 56 option for our not-Centrex customers.

To increase the availability of Switched 56 service, SDS 56 will be 
provided using either two- or four-wire technology.  The distance 
from your central office (where the telephone switch is) will 
determine which of these technologies will be used -- the four-wire 
option extends the service farther.

You can call the Switched Data hotline at 800-995-0346 to find out 
about availability for your telephone prefix.

Pacific Bell will work with the inter-exchange carrier (IEC) of your 
choice, who provides the long distance portion of your transport.

TO GET MORE INFORMATION
-----------------------------
Contact your Pacific Bell account team for more information.  

For fax-back information on any of Pacific Bell's switched digital 
products,  call 800-995-0346.  The fax-back system has diagrams and 
other information not on this BBS.

Application example diagrams are available on this BBS for 
download.  Go to the main menu and visit the FILES FOR DOWNLOAD area.



** Product names mentioned herein may be trademarks and/or 
registered trademarks of their respective companies.**

