Path: utzoo!telecom-request Date: 11 Apr 91 18:45:47 GMT From: Andy Sherman Newsgroups: comp.dcom.telecom Subject: Re: Is a Data Conference Using Three-Way Calling Possible? Message-ID: Organization: AT&T Bell Laboratories, Murray Hill Sender: Telecom@eecs.nwu.edu Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 286, Message 1 of 10 Lines: 48 In article leryo@gnu.ai.mit.edu (Leryo Malbito) writes: > Would anyone know how one could set up a data conference using > three-way calling? This seems like an idea that would be not too > difficult to implement, although a friend and I have unsuccessfully > tried several times...... > [Moderator's Note: You cannot do what you want. The modem has only two > conditions: originate and answer. It cannot talk to another modem set > in the same mode. Any two of the three can communicate if one is set > to receive and the other to transmit. The third one will be (possibly) > able to talk to one or the other, but not both. What usually happens > is the third modem, in generating its own originate or answer carrier > makes the connection so cluttered with noise that none of the three > can communicate, as you have found out. I said modems have only two > modes: this is not entirely true. My US Robotics Courier 2400 has a > third mode called 'transmitter off', allowing it to sit there and > silently monitor what is happening otherwise. So with such a modem, > you could bring a three-way data connection up successfully provided > the third party sat there silently and did not throw carrier at the > other two. PAT] Well, certain types of data conference calls can be set up, but the cost is probably too high for BBS'ing. I don't have the details, but AT&T's Alliance(tm) Teleconferencing service has some kind of bridge modem set up to allow graphics to be shared by multiple sites. You need a special modem on your end to do it, and you dial into the Alliance bridge. I believe the bridge re-broadcasts data to all participants in the conference. The AT&T OVERVIEW(tm) scanner supported this service to allow the sharing of scanned documents with remote pointing. Andy Sherman/AT&T Bell Laboratories/Murray Hill, NJ AUDIBLE: (201) 582-5928 READABLE: andys@ulysses.att.com or att!ulysses!andys What? Me speak for AT&T? You must be joking! [Moderator's Note: A notable example of a 'data conference call' would be the CB Simulator program on Compuserve. And yes, it is expensive to use. But there you have an example of how such a thing would be done with three or more parties. Instead of a direct link between modems however, what happens is each party transmits to a central computer, and that computer then parcels everything back out again, usually instantly or nearly so. PAT]