Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!killer!vector!nobody From: sleat@ardent.UUCP (Michael Sleator) Newsgroups: comp.dcom.telecom Subject: Re: In use light Summary: try an exclusion circuit instead Message-ID: Date: 14 Oct 88 06:51:18 GMT References: Sender: chip@vector.UUCP Reply-To: sleat@ardent.UUCP (Michael Sleator) Organization: Ardent Computer Lines: 28 Approved: telecom-request@vector.uucp X-Submissions-To: telecom@bu-cs.bu.edu (TELECOM Digest Coordinator) X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) X-TELECOM-Digest: volume 8, issue 162, message 2 In article jetzer@studsys.mu.edu (jetzer) writes: [discussion of indicator light to show phone off hook] >I would also be interested in such a device - my roommate has this >nasty habit of picking up the phone while I'm using my modem. Seems to me that maybe what you need is an "exclusion circuit". You can buy these (from Radio Smack?) or make one with an SCR, a Zener diode, and a resistor. It works as follows: The circuit is put in series with a phone or modem. If the line is in the on-hook state and the phone goes off-hook, the phone is connected as normal. However, if the line is already off-hook, then the phone is completely dead. As a side effect (at least with the circuit I use), if the line is off-hook and the phone is taken off-hook, and then the other load that was holding the line off-hook goes on-hook, the previously dead phone gets the line before it goes on-hook. (If you can follow that description...) Thus, hanging up the phone that was on the line immediately transfers the line to the waiting phone without dropping the call. I also tend to put a bypass switch on a phone when I install one of these, so that if I deliberately want to break in, I can. I put these things on phones and modems whenever they share a line so that people don't trash the data and so that when uucp fires up it doesn't blast people off the line. Works like a charm. Michael Sleator Ardent Computer ...!{decwrl | hplabs | ubvax | uunet}!ardent!sleat