ISDN to non-ISDN Connection -- Questions

: Tilman Schmidt < <snip : Bell Atlantic has installed modem
: pools at larger CO's which are accessible from among other things the D
: channel of an ISDN line.

Interesting, but who and how does that modem pool serve? Do I (an ISDN
user) connect through that (remote CO) pool to a POTS modem user? If so,
how does that POTS modem user initiate the call to me?

What's a good source of info on that service? Someone at Bell Atl? The
Bellcore pkg doesn't address it.

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I don't know about other areas, but Bell Atlantic has installed modem
pools at larger CO's which are accessible from among other things the D channel
of an ISDN line.
Regards,
Joe McGraw ()

If you were thinking of a connection between an ISDN number and a
POTS number that would look like a data connection on the ISDN side
- no way. Only voice connections can cross the border between ISDN
and POTS. Theoretically, telcos could have installed banks of
modems to convert data calls between the two networks, just as they
installed banks of A/D-D/A converters to convert voice calls, but
that would be much more expensive because of the variety and
ongoing evolution of modems. The demand is probably just not big
enough to justify the effort.

So the only option you have is to make a voice connection and
perform the modem functions on the ISDN end with your own
equipment. There are two ways to do this:

1. You hook a real modem to an a/b Terminal Adapter. The two
modems will never know that the voice connection between
them actually goes through ISDN.

2. You do the modulation/demodulation digitally by applying the
appropriate algorithms to analyze the digitized modem signal
you get out of the ISDN end of the connection, and synthesize
digitally the waveform that the modem on the POTS end will
understand, after the D/A conversion done for you by the ISDN
to POTS gateway. This is what ISDN cards like the IBM
WaveRunner do. It is of course much more difficult to
implement and needs considerable processing power on the ISDN
card, but has the potential for better transmission quality
because you get rid of one A/D-D/A conversion (in the a/b
Adapter).

HTH
Tilman

--
Tilman Schmidt Phone: +49 221 8299 275
Sema Group Deutschland GmbH Fax: +49 221 8299 266
Siegburger Str. 215, 50679 Koeln, Germany E-Mail:

There are a number of cases.

1. If you call from an ISDN telephone the call will be connected and you will
hear the modem beep in your ear.

2. If you have a modem connected to an analog port on an ISDN TA or if you
have a digital modem (a la IBM Waverunner) you will get a connection and the
modems will communicate if they are compatible.

3. If you call using an ISDN circuit mode data device you will not be able to
complete the call because the bearer services are not compatible.

1. If you call from an analog phone the call will be connected an you will
hear the modem beep in your ear.

2. If you call from a modem you will get a connection and the modems will
communicate if they are compatible.

Did I understand you question?

Bob Larribeau
Consultant
San Francisco

In note <31mtl6$@news1.digex.net writes:
Normal... A 14,400bps modem would get... 14,400 bps 8-). Flow control,
RTS/CTS is normal... Basically it acts like a normal line (except probably
somewhat cleaner than man since the coax is eliminated or at least greatly
reduced.) Oh.. spent too much time in alt.radio.cb and ham 8-)... I meant the
copper 8-).