Path: utzoo!telecom-request Date: 6 Jun 91 03:20:53 EST From: "Barton F. Bruce" Newsgroups: comp.dcom.telecom Subject: Re: Busying Out a Phone With a Resistor? Message-ID: Organization: Cambridge Computer Associates, Inc. Sender: Telecom@eecs.nwu.edu 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 1 of 9 Lines: 42 In article , mju@mudos.ann-arbor.mi.us (Marc Unangst) writes: > 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 Back in pre-electronic days, your line was apt to be fed by a balanced pair of 200 ohm relay windings fed 48 volts DC. That is 400 ohms total, and a short rignt in the CO would pull 120 ma. Many 1A2 KTU cards used a 135 ohm 5 watt resistor for hold. If that resistor were to be put right across the line in the CO, it would only get 1.1 watts. Any farther out on the loop, obviously gets less. Sure there were dial long line units that used 96 volt battery, but those were on LONG LINES. At the other end, a TT pad spec expects 23 ma min to work. Sure many run with less. If you were on a VERY long loop, you might want something lower that you picked to really hold the line busy reliably. For years our NYC office busied ALL lines except the first at night. The answering machine was on the first line, and 135 ohm resistors were slammed across all others by a 12 pole wire spring relay. If they went up on permanent signal,and 'dropped a card' each night, so what. Every morning everything would go back to normal. If the test board ever looked at it, they soon knew what to expect and ignored it. I bet in NYC they never noticed. Today I never bother with a resistor. Take a four inch piece of modular cord, crunch a plug on one end, strip the outer jacket about an inch on the other, and stuff the two center wires into a 'chicklet' (eight connector, or whatever) and squeeze it in a presser to connect T + R together. This will never fail to busy a loop start line. There is no reason to try to be 'nice' with a resistor. To busy a ground start line, you could just ground ring, but for several reasons it is best to ground BOTH tip and ring. The simple answer is just short Tip to Ring and be done with it.