Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!killer!vector!nobody From: wheels@mks.uucp (Gerry Wheeler) Newsgroups: comp.dcom.telecom Subject: Re: sensitive relay wanted Summary: voltage measurement won't do Message-ID: Date: 30 Sep 88 13:57:40 GMT References: Sender: chip@vector.UUCP Organization: Mortice Kern Systems, Waterloo, Ont. Lines: 25 Approved: telecom-request@vector.uucp (USENET Telecom Moderator) X-TELECOM-Digest: volume 8, issue 149, message 3 X-Submissions-To: telecom@xx.lcs.mit.edu (Mailing List Coordinator) X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) I originally asked about using a sensitive relay to detect which of two devices (phones, faxes, whatever) was offhook. (I didn't phrase it that way, but that was the gist of it.) In my situation, one will be a modem, and the other a fax. In article , kaufman@polya.stanford.edu (Marc T. Kaufman) writes: > You want to use a voltage comparator IC to measure the voltage between the > wires. I thought about that originally, but it won't work. It will tell me if either device is offhook, but not which one because they're wired in parallel. > Simpler, for a single phone, is to see if the phone has > a spare set of contacts on the hook switch (many do), and use them. Agreed. I think some Hayes type modems include an extra pair of contacts to be used on the A-A1 lines of a key system. However, it's not so easy to do with a fax. Unfortunately. -- Gerry Wheeler Phone: (519)884-2251 Mortice Kern Systems Inc. UUCP: uunet!watmath!mks!wheels 35 King St. North BIX: join mks Waterloo, Ontario N2J 2W9 CompuServe: 73260,1043