Path: utzoo!attcan!uunet!pyrdc!netsys!vector!nobody From: brian@umbc3.UMD.EDU (Brian Cuthie) Newsgroups: comp.dcom.telecom Subject: Re: sensitive relay wanted Message-ID: Date: 5 Oct 88 03:51:22 GMT Sender: chip@vector.UUCP Reply-To: brian@umbc3.UMD.EDU (Brian Cuthie) Lines: 19 Approved: telecom-request@vector.uucp (USENET Telecom Moderator) X-TELECOM-Digest: volume 8, issue 152, message 6 X-Submissions-To: telecom@xx.lcs.mit.edu (Mailing List Coordinator) X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) In article wheels@mks.UUCP (Gerry Wheeler) writes: >X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) > >I'm looking for a relay to place in series with a telephone which will >open (or close) when the set is offhook. The closest I've come is with >a 200 ohm 4.5 mA relay. It didn't affect the phone operation too much, >but wouldn't quite pull in. If I pressed the armature in, it would >latch. Close, but no cigar. > All you really need to do is use an Opto-Isolator. It is a good idea to either use an AC opto-isolator, or to use a full wave bridge rectifier in front of it.,Also, bypass the diode with a 470 ohm 1/2 watt resistor. This technique works quite well. If you need more info just call me. I hate trying to write a novel. -brian (301) 381 - 1718