Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!ntg!dplatt
From: dplatt@ntg.com (Dave Platt)
Newsgroups: comp.dcom.fax
Subject: Re: fax/phone switches ?
Message-ID: <1005@goblin.ntg.com>
Date: 7 Jun 91 17:03:48 GMT
References: <1991Jun4.225358.3684@athena.mit.edu> <1991Jun5.145752.16042@uni-paderborn.de> <1991Jun6.000911.14780@athena.mit.edu>
Organization: New Technologies Group, Inc.  Palo Alto CA
Lines: 27

In article <1991Jun6.000911.14780@athena.mit.edu> caserta@athena.mit.edu (Francesco Caserta) writes:

> No problem at all. Modems and faxes send acoustic signals that are
> specified in worldwide accepted standards. Depending on the signal they
> hear, they will switch to the right device. (There is some exception for
> some old equipment.)

Actually, I think it _is_ a problem.  It's true that faxes (Group 3, at
least) do send a specific tone every few seconds after they dial, and
that a fax-aware answering machine or switch can use this tone to route
the call to a fax machine.

The same is not necessarily true of data modems.  Most data modems do
_not_ send an "I am a modem" tone after dialing.  They wait, silent as
the grave, until they "hear" a suitable answer-tone from a modem at the
receiving end of the call, and _then_ they send one or more tones to
initiate the data handshake process.

The reports I've heard of fax/data/voice switches are not particularly
encouraging... one comment was "The vendors seem to assume that all
users have advanced degrees in telecommunications."


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