Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!uakari.primate.wisc.edu!brutus.cs.uiuc.edu!psuvax1!psuvm!psuecl!peg From: peg@psuecl.bitnet Newsgroups: sci.electronics Subject: Re: telephone light indicating use Message-ID: <61244@psuecl.bitnet> Date: 21 Oct 89 17:44:33 GMT References: <17263@watdragon.waterloo.edu> Distribution: na Organization: Engineering Computer Lab, Pennsylvania State University Lines: 32 In article <17263@watdragon.waterloo.edu>, sekoppenhoef@rose.waterloo.edu (Shawn E. Koppenhoefer) writes: > We have a phone at home that is shared between a computer and a person's > voice. Furthermore... we have several telephones on that particular phone > line. Is there some way of attaching an led or something to indicate > by being on that the phone is IN-USE ? Something to prevent family members Hello! A few years back, my roomates and I had something like this on our extension phones in a dorm suite. We built the circuit based on what someone else in the dorm was using--I can't say I knew how it worked (I know very little about phones!). As I recall, the circuit was simply-- |------->|-----| red lead ------resistor-------| |------ green lead |-------|<-----| where the -->|-- are LED's. Note that they are connected in opposite directions. If I remember right, the LED's flashed alternately when the phone rang (nifty with two different color LED's! :) and one would stay on when the extension was off-hook. It seems rather obvious how this would work--if phones work in an obvious manner! Anyway, this is certainly a cheap approach. The resistor value you will have to find experimentally--start large! I think the phone ringing voltage is ~100 volts, so maybe 5k ? And finally, it may be illegal to connect this circuit. It never caused any trouble with our phone system, but I can't guarantee it won't affect yours. Maybe you could try it for a while and see what happens. Best of luck! Paul