Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!samsung!usc!apple!fox!portal!cup.portal.com!Howard_Reed_Johnson
From: Howard_Reed_Johnson@cup.portal.com
Newsgroups: comp.sys.ibm.pc
Subject: Re: Modems and Telephone Lines
Message-ID: <24370@cup.portal.com>
Date: 23 Nov 89 03:25:52 GMT
References: <13410@eerie.acsu.Buffalo.EDU>
  <1989Nov20.135228.2503@ug.cs.dal.ca>
  <1989Nov20.200531.8246@esegue.segue.boston.ma.us>
Distribution: na
Organization: The Portal System (TM)
Lines: 18

cook@sybil.cs.Buffalo.EDU (John M. Cook)
 writes <13410@eerie.acsu.Buffalo.EDU>:
> A friend added a modem to his computer at the office and the phone line
> is part of a PBX.  The problem is he is only using the two transmission
> wires so when he uses the modem the light for that line doesn't lite on
> the phones in the office.

johnl@esegue.segue.boston.ma.us (John R. Levine)
 writes <1989Nov20.200531.8246@esegue.segue.boston.ma.us>:
> The original question was about a key system where there is an in-use
> light on the phone for each line; that takes an RJ12 or RJ13 where the
> third and fourth wires are for the in-use relay, in which case the
> center two wires (red and green) are for the phone and next two (yellow
> and black) are the A and A1 wires which the modem needs to short
> together while it's using the phone.

Most modems which support RJ-12 or RJ-13 lines accept the Hayes command
AT&J1 for operating on such lines.