Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: Dave Levenson Newsgroups: comp.dcom.telecom Subject: Re: Basic Questions About Telephones Message-ID: <10721@accuvax.nwu.edu> Date: 11 Aug 90 12:50:15 GMT Sender: news@accuvax.nwu.edu Organization: Westmark, Inc., Warren, NJ, USA Lines: 78 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 560, Message 3 of 3 In article <10692@accuvax.nwu.edu>, drears@pica.army.mil (Dennis G. Rears (FSAC)) writes: > It seems as if each telephone cable contains four wires (red, > green, black, and yellow). For one line only the red and green wires > are used. The black and yellow wires are only used for the second > line. If only one line is installed in a jack why do the yellow and > black wires have to be attached? I suspect it doesn't. The extra wires are installed for ancillary services. This may include a second line, a lighted dial, a ground lead (used for selective ringing and party identification on multi-party lines). On new service, these days, they install four-pair (eight wire) cable -- it's cheaper to put in extra wires at the time of the initial installation than to put them in later, when the customer needs them. > The modular jack that goes into the phone has four wires in it. Why > is that, if only the red and green are required for service? Just in > case you have a two line phone? See above. > Why is the jack that goes from the telephone headset to the > telephone a different size than the jack that goes from the phone to > the wall jack? Is it to idiotproof the process? Also why four wires > into the headset? Does the phone itself do anything to the signals > before it sends it to the headset? If the proper size jack was put on > the headset could you plug that into the wall jack and recieve calls? The handset has four wires -- a two-wire circuit for the microphone, and another two-wire circuit for the receiver. Your line from the central office, as you have already noticed, has two wires. The bidirectional audio signals on these two wires are separated by a circuit called a hybrid, located in the telephone instrument. It separates the transmit and receive audio information and provides the derived four-wire path to the handset. > What do the two wires (red and green or yellow and black) carry? Is > one postive and negative like electrical wires? The two wires deliver DC power to operate your telephone set. They also carry AC voice signals. The red wire should be at ground potential, and the green wire should be at -48 volts. > In the case of my second line I bought a double wall phone outlet. I > installed the first line (R&G) to the top outline and installed the > second (B&Y) line to the bottom outlet. The first line worked the > second did not. > wrong with the Yellow or Black wires. That seems strange to me as all > four wires are in the same cable and if there was a physical break in the > cable it would affect all the wires, not just one or two. Any thoughts > of this? If you wired the B-Y pair to the red and green terminals on the second jack, then you probably have an open black or yellow wire in your cable. If the B-Y pair is connected to the black and yellow terminals on the second jack, connect it to the the red and green terminals on the second jack, and it will work better. It's not unusual for one wire to become defective in a multi-wire cable; that's another reason why they install extra conductors. > P.S. Does anybody know the number for ringback for 609-871-XXXX? I suggest that you try 550-XXXX, 551-XXXX, 552-XXXX etc. XXXX would be the last four digits of your telephone number. If you get a busy signal, try the next one in the sequence. If you get a dialtone after dialing, flash your switchhook. If you then get a high tone, hang up and your phone should start to ring. To stop the ringback, just answer and then hang up for at least ten seconds. Dave Levenson Voice: 908 647 0900 Fax: 908 647 6857 Westmark, Inc. UUCP: {uunet | rutgers | att}!westmark!dave Warren, NJ, USA AT&T Mail:!westmark!dave