Dec 122017
A collection of text files about ISDN.
File ISDNTXT.ZIP from The Programmer’s Corner in
Category Tutorials + Patches
A collection of text files about ISDN.
File Name File Size Zip Size Zip Type
FAQISDN.TXT 21260 8684 deflated
HISDN.TXT 11561 4436 deflated
ISDN.TXT 25129 8256 deflated
ISDNJP 1535 828 deflated
ISDNPAP.TXT 7559 3422 deflated
ISDNTEST.TXT 6592 2803 deflated
SUNISDN.TXT 19652 6794 deflated

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Contents of the FAQISDN.TXT file

Newsgroups: comp.dcom.isdn,news.answers
Subject: ISDN Frequently Asked Questions (and Answers) [Monthly posting]
From: [email protected] (Sean N. Welch)
Followup-To: comp.dcom.isdn
Reply-To: [email protected] (Sean N. Welch)
Organization: Experimental Computing Facility, U.C. Berkeley
Keywords: ISDN FAQ
Approved: [email protected]
Summary: This posting contains a list of Frequently Asked
Questions (and their answers) about Integrated Services
Digital Networking (ISDN). It should be read by anyone
who wishes to post to the comp.dcom.isdn newsgroup.

Archive-name: isdn-faq
Last-modified: 1992/07/10
Version: 1.0

This is the first official monthly posting of this comp.dcom.isdn FAQ.
Thank you all for your feedback on the initial draft. (That is not to
say that this is finished by any means. Comments and suggestions are
always welcome.)

There have been a number of additions and a few corrections since the draft
and the questions and answers are no longer direct quotes. As new information
was brought to my attention, it became difficult to integrate direct quotes.
If there are any problems with my editing as opposed to quoting, I'm sure
someone will let me know. Now I just cite the sources at the end of each
question. It still reads like it was written by 40 different people (because
it was) but after a few revisions, I hope to have a much smoother document.

I'm currently working on two additional questions having to do with the
nitty-gritty of how ISDN is carried and Switched 56 Kbps (S56) as it
relates to ISDN. Look for them next month.

[Note to the moderator of news.answers: Sorry for all the trouble. Thanks.]

Sean N. Welch \\/ [email protected]
Experimental Computing Facility /\\ University of California, Berkeley

Frequently Asked Questions and Answers

These questions and answers have (for the most part) been extracted from

Questions with answers:

1) What is ISDN?
2) What does an ISDN network look like?
3) What is ATM?
4) What will it look like in my house/office?
5) How does this compare to regular phone line services?
6) Is caller ID available on ISDN?
7) What do I get above and beyond plain old telephone service?
8) What do ISDN phones cost?
9) Can you use existing telephone equipment with the voice portion?
10) How do I find out about getting ISDN in my area?
11) Where can I find what all of these acronyms mean?
12) Who is shipping what?
13) How about that SPARCstation 10?
14) Why does certain ISDN TE only work with a specific ISDN switch?
15) Where can I read more?
16) Who do I have to thank for this list?

Questions for which I have not yet put together an answer, but for which I
am accepting suggestions:

a) What is ISDN-1?
b) What is the status of ISDN-1?
c) What is B-ISDN and what does it have to do with ISDN?

Suggestions for additional questions and answers are appreciated.


1) What is ISDN?

ISDN stands for "Integrated Services Digital Networks", and it's a CCITT
term for a relatively new telecommunications service package. ISDN is
basically the telephone network turned all-digital end to end, using
existing switches and wiring (for the most part) upgraded so that the
basic "call" is a 64 kbps end-to-end channel, with bit-diddling as needed
(but not when not needed!). Packet and maybe frame modes are thrown in
for good measure, too, in some places. It's offered by local telephone
companies, but most readily in Australia, France, Japan, and Singapore,
with the UK and Germany somewhat behind, and USA availability rather spotty.

[email protected] (Winston Seah)
[email protected] (Fred R. Goldstein)
[email protected] (Paul Antoine)

2) What does an ISDN network look like?

A Basic Rate Interface (BRI) is two 64K bearer ("B") channels and a single
delta ("D") channel. The B channels are used for voice or data, and the D

channel is used for signaling and/or X.25 packet networking. This is the
variety most likely to be found in residential service.
Another flavor of ISDN is Primary Rate Interface (PRI). Inside the US, this
consists of 24 channels, usually divided into 23 B channels and 1 D channel,
and runs over the same physical interface as T1. Outside of the US then PRI
has 31 user channels, usually divided into 30 B channels and 1 D channel.
It is typically used for connections such as one between a PBX and a CO or

[email protected] (Kevin Collins)
[email protected] (Dave Evans)
[email protected] (Andrew Scherpbier)

3) What is ATM?

ATM (Asynchronous Transfer Mode) is a switching/transmission technique
where data is transmitted in small, fixed sized cells (5 byte header,
48 byte payload). The cells lend themselves both to the time-division-
multiplexing characteristics of the transmission media, and the packet
switching characteristics desired of data networks. At each switching
node, the ATM header identifies a "virtual path" or "virtual circuit"
that the cell contains data for, enabling the switch to forward the
cell to the correct next-hop trunk. The "virtual path" is set up
through the involved switches when two endpoints wish to communicate.
This type of switching can be implemented in hardware, almost essential
when trunk speed range from 45Mb/s to 1Gb/s.

For more information, read comp.dcom.cell-relay.

[email protected] (Art Berggreen)

4) What will Basic Rate (2B+D) ISDN look like in my house/office?

An ISDN BRA U-Loop is 2 conductors from the CO to the customer premises.
At the customer premises the U-loop is terminated by an NT1 (network
termination 1). The NT1 drives a T-bus which is 4 wires. You can only have
one device on the T-bus. If you run the T-bus into a NT2 which has an S-bus
(the passive bus) on the other side, you can connect up to 8 physical devices.
Electrically, the S and T reference points are the same (which is why they are
almost always referred to as the S/T bus).
Some NT1 may include between 24v and 53.5v power on the T-bus (making it 6
wires), however this would be model/vendor dependent. There are also 8 wire
T-bus connection (power + 2 extra?).
Australia and Europe are similar except the NT1 is owned by the PTT. Either
a ECH (Echo Canceling Hybird), like is used in the US, or a form of time
division multiplexing using AMI is used to achieve bidirectional transmission
an a single pair.

+-+ S Bus +-------+ T Bus +-------+ U Loop |
|?|=-=-=-=-=-=| NT2 |===========| NT1 |--------------[| wall
+-+ 4-8 wires +-------+ 4-8 wires +-------+ 2-4 wires |

Some ISDN hardware plugs into the U loop, some with the T Bus, and
some with the S-Bus. In the US (at least) there is a power supply
between the wall and the NT1.

[email protected] (Cliff Frost)
[email protected] (Curt Welch)
[email protected] (Dror Kessler)
[email protected] (Greg Larson)
[email protected] (Paul Antoine)
[email protected] ( Patton M. Turner)
[email protected] (Ronnie B. Kon)

5) How does this compare to regular phone lines?

The ISDN line may act like two independent phone lines with two numbers.
Depending on the CO equipment, conferencing features etc. may be available
(conferencing in the telephone switch). BRA ISDN phones can support key-set
features such as you would expect to get on an office PBX like:
- multiple DNs / lines.
- conferencing features.
- forwarding features.
- speed call.
- call park.
- call pickup.
- ring again.

[email protected] (Curt Welch)
[email protected] (Greg Larson)

6) Is caller ID available on ISDN?

Caller ID (name or number display) may be supported (depending on the
CO setup). The availability of caller ID for residential phones would
depend on the capabilities of the local phone network and legislation
allowing or disallowing caller ID.

[email protected] (Curt Welch)
[email protected] (Greg Larson)

7) What do I get above and beyond plain old telephone service?

One of the main features it that instead of the CO sending an AC ring
signal to activate your bell, it sends a digital package that tells WHO
is calling (if available), WHAT TYPE of call (speech, datacomm?), the
NUMBER DIALLED (maybe one of your aliases) and some other stuff. Your
equipment can then analyze this stuff and make an "intelligent" decision
what to do with it. For example, a phone (with speech-only capacity)
would completely ignore a datacomm call while a Terminal Adapter (ISDN
"modem") or a phone with built-in datacom functions would respond to it.
If you have several "aliases" tied to your line, you can program certain
phones to answer calls for certain numbers only. Datacomm calls contain
baud rate and protocol information within the setup signal so that the
connection is virtually instantaneous (no messing around with trying
different carriers until both ends match).

[email protected] (Curt Welch)
[email protected] (Torsten Lif)

8) What do ISDN phones cost?

The ISDN sets can cost between $180 for an AT&T 8503T ISDN phone from
Pacific Bell up to $1900 depending on what/how many features are needed.

[email protected] (Dave Evans)
[email protected] (Brad Huntting)
[email protected] (Joe Ilacqua)

9) Can you use existing telephone equipment with the voice portion?

Terminal Adapters (TA'a) are available that will interface non ISDN terminal
equipment (TE), called TE2 to the S/T interface. At least one RBOC provides
a modem pool to allow for interchange of data with POTS subscribers. Bellcore
may approve a standard to allow a analog pair to interface to POTS sets from
a NT1. Also w/o a NT2 only one set can be connected to a B channel at a time. This prevents 2 sets from participating in the same voice call.

[email protected] ( Patton M. Turner)
[email protected] (Joe Ilacqua)

10) How do I find out about getting ISDN in my area?

I work in the industry and suggest that you call the local telephone service
center office and ask for the name and number of the Marketing Product Manager
for ISDN services. If the service rep cannot make heads or tails of your
question, ask to speak to the local service center manager for complex
business services. This person should be able to direct you to the right
place. For the Bell companies, this position is normally part of the
telephone company's core marketing staff at their headquarters location.

[I had been planning on listing particulars about local people to contact,
but since people change jobs and I wasn't planning on continually verifying
the names and numbers, instead I'll stick with listing the following.]

Bellcore national ISDN information clearing house hotline
800 992 4736

North American ISDN Users Forum (NIU) is an org. of ISDN-interested
parties, coordinated by NIST (National Institute of Stds. and Tech.)
Contact: Shukri Wakid
Advanced Systems Division
Gaithersberg, MD
(301) 975-2937/4853

[email protected] (Ben Harrell)
[email protected] (Eric A. Litman)
[email protected] (Marc Evans)
[email protected] (Al Varney)

11) Where can I find what all of these acronyms mean?

An archive of telecommunication related files are maintained on in the telecom-archives sub directory. There is a
glossary of general telecom acronyms, as well as an ISDN specific

[email protected] (Joe Smith) asks:
[email protected] (Peter M. Weiss)

12) Who is shipping what?

[In this section, I'd like to expand a list of vendors shipping products
related to work in ISDN. As it stands, the number is small, and the
information is sparse. Additions and corrections are most welcome.]

[Also - Network World from November 18th, 1991 has an extensive listing
of products that were available at that time. It ranges from terminal
adapters and PC cards to handsets to VME boards. I'm in communication
with them trying to get permission to reproduce parts of the article

Digital Subscriber Controler
AMD79C30A ISDN chip
Combines IEEE 1.430 S/T interface transceiver B channel LAPD channel
processor and audio processor in a single chip.
Advanced Micro Devices
901 Thomson place
Mailstop 126
Sunnyvale, CA 94086
(408) 732 2400 (voice)

ISDN <-> other network converters
333 West El Camino Real, Suite 310
Sunnyvale, California 94087
(408) 522 9020 (voice)
(408) 732 5497 (fax)

ISDN <-> other network converters
6400 Flying Cloud Drive
Eden Prarie, MN 55344
(612) 943 9020 (voice)
(612) 643 5398 (fax)

Q-bus board, router, and PC cards
Digital Equipment Co
DEC Park
Worton Grange

PC cards and standalone ISDN adapters
Cherry Hill Industrial Center
Building 9
Cherry Hill, NJ 08002
1 800 GANDALF (voice)

Terminal adapters
Hayes ISDN Technologies
501 Second St., Suite 300
San Francisco CA 94107
(415) 974-5544 (voice)
(415) 543-5810 (fax)
ISDN Product Manager: Chris Brock ([email protected])
ISDN Developer Support: Bill Taylor ([email protected])
ISDN Product Literature: Stephanie Lopez ([email protected])
ISDN Sales: Jon Hendricks ([email protected])

Terminal adapters
Motorola UDS
5000 Bradford Drive
Huntsville, AL 35805
(205) 430 8000 (voice)

PRI ethernet bridges
Network Express
Andrew Hasley
VP, Marketing
2200 Green Road
Ann Arbor, MI 48105
(313) 761-5005 (voice)
(313) 995-1114 (fax)

Multi-protocol router
Spider Systems
UK France Germany
Spider Systems Limited Spider Systems SA Spider Systems Limited
Spider House Les Algorithmes Schadowstrasse 52
Peach Street Saint Aubin 91194 D-4000 Dusseldorf 1
Wokingham Gif-sur-Yvette Germany
England Paris Cedex
RG11 1XH France
0734 771055 (voice) (1) 69 41 11 36 (voice) (0211) 93 50 120 (voice)
0734 771214 (fax) (1) 69 41 12 27 (voice) (0211) 93 50 150 (fax)

Telrad Telecommunications, Inc.
135 Crossways Park Drive
Woodbury, New York 11797
(516) 921-8300
1 800 645-1350


13) How about that SPARCstation 10?

FYI, the hardware on the SS10 supports 2 B channels (64K+64K) and 1 D channel
(16K) for a grand total 144K in marketing speak. On *each* BRI (Basic Rate
Interface). The "DBRI" chip in the SS10 supports audio devices and *2*
Basic Rate Interfaces. Typically you might use both B channels for data,
1 channel for voice and 1 channel for data, or 1 channel for data to 1 point
and 1 channel for data to another point. In some parts of the world it's also
popular to run X.25 over the D channel.

Info from the SPARCstation 10 full announcement e-mail:

- What Becomes Available When:
Chip on the motherboard Q3 CY92
ISDN Drivers on Solaris 2.x Q4 CY92 Solaris 2.x
Teleservices API Q1 CY93 Solaris 2.x
Wide Area Networking software Q1 CY93 Solaris 2.x
The chip on the motherboard provides a BRI (basic rate interface)
ISDN connection that is integrated with workstation audio.
The drivers provide a low level interface to the hardware.
The Teleservices API enables application development for
workstation/telephony integration - providing functions like
call setup, transfer, hold, confer, etc. The API is hardware
independent so that it will work with third party non-ISDN
telephony hardware and software. The WAN software enables
data communication - running IP over ISDN (in other words,
applications that run over ethernet will run over ISDN).
In the first release, Sun will support data communications
in the US (for the AT&T 5ESS switch), the UK, France, Germany
and Japan. We will support voice services in the US (for
the AT&T 5ESS switch) only.

[email protected] (Dan Kegel)
[email protected] (Tom Kessler)

14) Why does certain ISDN TE only work with a specific ISDN switch?

In the bad current days before National ISDN-1, the ATT 5ESS switches and
Northern Telecom DMS100 switches speak different call setup dialogues. That's
why you will see ISDN TE listed as 5ESS, DMS100 or both.

[email protected] (Jim Rees)
[email protected] (Jerry Scharf)

15) Where can I read more?

"ISDN In Perspective"
Fred R. Goldstein
ISBN 0-201-50016-7

"ISDN: Concepts, Facilities, and Services"
Gary Kessler
ISBN 0-07-034242-3

"ISDN and Broadband ISDN" (2nd edition)
William Stallings
ISBN 0-02-415475-X

The 1990 ISDN Directory and Sourcebook
Phillips Publishing Inc.
7811 Montrose Road
Potomac, MD 20854
(301) 340-2100

ISDN Sourcebook
Information Gatekeepers Inc.
214 Harvard Ave,
Boston, MA 02134
(617) 232-3111
1 800 323-1088

Bellcore ISDN Availability Report
WR-NWT-2102 ($103)
800 521 2673

AT&T Technical Journal special issue on ISDN
(Volume 65, Issue 1) January/February 1986

[If anyone can tell me how to get ahold of the next two documents in terms
of either ISBN, a publishing company, or an ftp site, I'd appreciate it.]

"A subnetwork control protocol for ISDN circuit switching"
Leifer, Gorsline, & Sheldon

"Multiprotocol Interconnect on X.25 and ISDN in the Packet Mode"
Malis, Robinson, & Ullmann

EFFector. Issue 2.01, Issue 2.06, Issue 2.08

AT&T Documents
"5ESS( Switch National ISDN Basic Rate Interface
Specification - 5E8 Software Release"
AT&T document number 235-900-341

"5ESS( Switch ISDN Basic Rate Interface
Specification - 5E7 Software Release" {Custom BRI}
AT&T document number 235-900-331

"5ESS( Switch ISDN Primary Rate Interface
Specification - 5E7 Software Release"
AT&T document number 235-900-332

"5ESS( Switch Interface Specification to a
Packet Switched Public Data (X.75) Network -
5E8 Software Release" [as in CCITT X.75]
AT&T document number 235-900-317

"5ESS( Switch X.75' Intranetwork Interface
Specification - 5E8 Software Release"
[as in Bellcore's TR-000310]
AT&T document number 235-900-325

"5ESS( Switch Documentation Description
and Ordering Guide"
[list/description of 5ESS documents]
AT&T document number 235-001-001

AT&T documents ordering:
1-800-432-6600 USA
1-800-225-1242 Canada
+1 317 352-8557 elsewhere
AT&T Customer Information Center
Order Entry
2855 N. Franklin road
Indianapolis, IN 46219
(317) 352-8484 (fax)

Northern Telecom Documents

NTP 297-2401-100 ISDN System Description
NTP 297-2401-010 ISDN Product Guide


16) Who do I have to thank for this list?

Lots of people, in one way or another.

[email protected] (Winston WL Sorfleet)
[email protected] (Jim Rees)
[email protected] (Peter M. Weiss)
[email protected] (Mathias Gaertner)
[email protected] (Alan Palmer Stephens)
[email protected] (Art Berggreen)
[email protected] (Albert Willis)
[email protected] (Ben Harrell)
[email protected] (Michael Klein)
[email protected] (Cliff Frost)
[email protected] (Craig Partridge)
[email protected] (Curt Welch)
[email protected] (Dan Kegel)
[email protected] (Dror Kessler)
[email protected] (Dwight Ernest)
[email protected] (Greg Earle - Sun JPL on-site Software Support)
[email protected] (Winston Seah)
[email protected] (Eric A. Litman)
[email protected] (Torsten Lif)
[email protected] (Marc Evans)
[email protected] (Greg Larson)
[email protected] (Fred R. Goldstein)
[email protected] (Brad Huntting)
[email protected] (Jerry Scharf)
[email protected] (Jonathan I. Kamens)
[email protected] (Joe Smith)
[email protected] (Tom Kessler)
[email protected] (Kevin Collins)
[email protected] (Dave Evans)
[email protected] (Kevin Paul Herbert)
[email protected] (Laurence V. Marks)
[email protected] (Paul Antoine)
[email protected] (Patton M. Turner)
[email protected] (Rachel Willmer)
[email protected] (Rob Davies)
[email protected] (Wade T. Rogers)
[email protected] (Ronnie B. Kon)
[email protected] (Sanjay Manandhar)
[email protected] (Joe Ilacqua)
[email protected] (Toby Nixon)
[email protected] (Andrew Scherpbier)
[email protected] (Al Varney)
[email protected] (David Lesher)

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