Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!elroy!jato!jade!morris
From: morris@jade.jpl.nasa.gov (Mike Morris)
Newsgroups: comp.dcom.modems
Subject: Re: Phone busy with Modem signalling
Message-ID: <1242@jato.Jpl.Nasa.Gov>
Date: 11 May 89 04:08:05 GMT
References: <8905090741.AA18208@ucbvax.Berkeley.EDU>
Sender: news@jato.Jpl.Nasa.Gov
Reply-To: morris@jade.Jpl.Nasa.Gov (Mike Morris)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 43

Jeff Sicherman,CSU Long Beach writes:
>
>  I know this question involves ANCIENT equipment but I need an answer
>involving no hardware replacement (of modem or phone), extra hardware
>is OK.
>
>   Specifically, we have a 1200 baud, Racal-Vadic VA 3451 modem and a
>multiline, button controlled, 1A2-type phone system. The modem is used
>infrequently and shares one of the voice lines. (It is kept in manual
>answer mode.) When it is in use, we would like it to light the button
>on the phone system for that line - which it currently does not do, so
>people occasionally interrupt the modem call and file transfers.
>
>    As a last resort, if there are EXTERNAL modems that will do the job,
>we might consider replacement. Internal modems are OUT (modem is shared).
>Switching the phone system is definitely not possible at this time. What
>I am really looking (probably wishing) for though, is a Radio-Shack type
>gatchit to do this (fruitlessly, probably).
>
>  jeff Sicherman

What you need is a Radio Shack 43-117.  It is no longer in the catalog,
but _might_ be available if special ordered.

It is essentially a sensitive relay that is connected in series with the
modem, bypassed with a capacitor (for AC).  Physically it consists of
a small box with a RJ-11 jack in one end, and a short modular male-ended
cord coming out of the other end.  You simply plug the cord from the 
modem into this device, and the device into the phone system.  Each line
on your phone uses 3 pairs - first is the audio circuit, second is 
"activity" signaling (shorted for off hook), and the third is the lamp volatge.
This device simply provides a short for the second pair when the first pair
is in use (by the modem).

PS - If you find any, let me know! I need 3 or 4 myself.

I'll be happy to draw up any connections you need - just describe
what you need in mail.

US Snail:  Mike Morris                    UUCP: Morris@Jade.JPL.NASA.gov 
           P.O. Box 1130                  Also: WA6ILQ
           Arcadia, Ca. 91006-1130
#Include disclaimer.standard     | The opinions above probably do not even