Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!mcsun!ukc!tcdcs!dce.ie!ch
From: ch@dce.ie (Charles Bryant)
Newsgroups: comp.dcom.modems
Subject: Re: Conferencing modems
Message-ID: <1991Jan17.131856.17467@dce.ie>
Date: 17 Jan 91 13:18:56 GMT
References: <1991Jan12.055735.18719@beach.csulb.edu>
Organization: Datacode Communications Ltd, Dublin, Ireland
Lines: 26

In article <1991Jan12.055735.18719@beach.csulb.edu> sichermn@beach.csulb.edu (Jeff Sicherman) writes:
>
>  Protocols and other software issues aside, is it possible or practical
>to have a conference call with modems ? No real need or application but
>interested in the electronic and telephony issues.

There have been networks that work like that. I believe that bank's ATMs
use such a system. Their system is multidrop. This is leased-line based,
but with conference-calling it should work over dialup. The modems must
work in half-duplex mode (typically V.23 for 1200, V.26 for 2400 etc).
The protocol determines who talks at any given time (e.g. a 'master' may
poll each station in turn). You could set up a dialup broadcast network
(like an ultra low speed Ethernet!) with conference calling. Of course
modems such as V.32 which can't operate in half-duplex mode wouldn't
work, and many cheap PC modems don't work in half-duplex either.

The applications would be very limited. If you want to connect A, B, and
C, a conference-call based network would only be worthwhile if it was
cheaper than two links A-B and B-C, and the traffic between the three was
related (otherwise its easier to make two seperate calls). e.g. some
application sends requests from A to B, which triggers a request from B
to C, which replies to A.
-- 
Charles Bryant (ch@dce.ie)
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