Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!spool.mu.edu!telecom-request From: dxis.att.com!k2ph@pacbell.com (Bob Schreibmaier) Newsgroups: comp.dcom.telecom Subject: Re: Busying Out a Phone With a Resistor? Message-ID: Date: 6 Jun 91 13:49:11 GMT Article-I.D.: eecs.telecom11.434.4 Sender: Telecom@eecs.nwu.edu Organization: TELECOM Digest Lines: 28 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 434, Message 4 of 9 mju@mudos.ann-arbor.mi.us (Marc Unangst): > I recently had one modem in the middle of a 15-line hunt group go out. > Not wanting to move the rest of the modems up a line each, I did some > investigation with a VOM and a telephone, and discovered that plugging > a 270 ohm resistor into the phone line (across tip and ring) should > have almost the exact same effect as an off-hook telephone does -- > thus busying out the line. Now, my question is, is there anything > wrong with doing something like this? Will a 1/2W resistor be enough? > Is this an "accepted" way of busying out a phone line? On most lines the 1/2 watt resistor would be plenty. However, if you happened to be REAL close to a central office you could see as much as 24 volts across the resistor and, therefore, might have to dissipate as much as two watts. As long as you have that VOM handy, measure the voltage across the 270 ohm resistor. Then, square the voltage reading and divide by 270. That is the amount of power you are asking the resistor to dissipate. Should be 1/4 watt or less if you want to use a 1/2 watt resistor (safety factor of two). By the way, I have used this trick myself and it seems to work. Doesn't seem to be any problem with the telco "siren" signal that they put on off-hook lines that are not calling anyone. Bob Schreibmaier K2PH | UUCP: ...!att!dxis!k2ph a.k.a. "The QRPer" | Internet: k2ph@dxis.att.com Middletown, New Jersey | ICBM: 40o21'N, 74o8'W