eric@chronon.UUCP (Eric Black) (03/07/86)
In article <584@mmm.UUCP> mrgofor@mmm.UUCP (MKR) writes: >In article <237@micropro.UUCP> edg@micropro.UUCP (Ed Greenberg) writes: >>In article <714@bonnie.UUCP> dnc@bonnie.UUCP (Don Corey) writes: >>>I needed to buy some coiled line cords a few months ago. While all of the cords >>>I looked at had four connector jacks on them, some of them only had two wires >>>in the cord. Radio Shacks cord had four wires. A telephone only uses two wires, >>>but I needed four wires for my application. Just as an aside, one of the three >>>cords I bought from Radio Shack was defective. >>>Don Corey >>>AT&T Bell Laboratories >> >>My telephone, (A Western Electric 2500 set with the ubiquitous >>"BELL SYSTEM PROPERTY -- NOT FOR SALE" stampted in the baseplate, has >>four wires running from the modular connector in the handset to the four >>connection points (two each for mouthpiece and earpiece.) >> >>Most every telephone I know of had the same connection. Most standard >>sets have one wire each from the earpiece and mouthpiece connected to >>the same screw on the network box (I forget which one.) Thus, a set >>could actually be wired with a 3 conducter cord and a jumper in the >>earpiece. I have never seen a telephone set with two wires for the >>handset. (I've never even seen one with 3.) >> >>Taco Bell: Part of the nationwide Bell System! >>-- > > Every time I've moved, I've wired up the new phones in my new house, >and I've done it for friends, too - and I have never had to use more than two >wires for any phone - even in a two-line house. > >-- > --MKR A phone line (and therefore the connection of the phone to it) requires two wires for talk current. The power to ring the bell has to come from somewhere as well. Non-party-lines bridge the 80-130 VAC for the ringer over the same two wires as carry the DC talk power. A capacitor in the network (the encapsulated circuit contained in that box with all the screw terminals on it) handles passing the AC ring current to the bell and blocking the DC. Party lines provide the ring current slightly differently. Instead of using the same two wires, the ring current uses ONE of the talk wires, and uses earth ground for its return. This is why (up until just recently) phones had three wires, red, green, & yellow, for connection to the phone line. The red and green are the talk wires, just as now. The ringer, however, is connected between the yellow wire and either the green or the red wire (the red wire as usually shipped). To install the phone on a normal line, the yellow wire is connected together with the green, and *poof* it's a 2-wire connection with the ring current coming over the talk wires. To install on a party line, the yellow wire is connected to local earth ground, and the other end of the ringer is connected to the red or green as appropriate. Note that the phone co. can selectively ring one phone or the other by imposing the ring current on either of the two talk wires and ground. For party lines with two parties this means nobody gets a ring meant for the other party. If there are more than two parties on the line, the long-short-count-'em codes for rings must be used. Party lines are no longer being installed, and existing ones are being converted to private single-party lines. Therefore there is no real need for three wires in the connecting cord for new phones, and they are disappearing. Extra features such as an illuminated dial require extra conductors, however, as pointed out above. -- Eric Black "Garbage In, Gospel Out" UUCP: {sun,pyramid,hplabs,amdcad}!chronon!eric VOICE: (415) 941-0403 US SNAIL: Chronon Computer Corp. 2570 El Camino Real W. Suite 206 Mountain View, CA 94040
begeman@milano.UUCP (03/10/86)
In article <173@chronon.UUCP>, eric@chronon.UUCP (Eric Black) writes: > For party lines with two parties this means nobody gets > a ring meant for the other party. If there are more than two parties > on the line, the long-short-count-'em codes for rings must be used. Not quite true. For my first 3 years in my farmhouse, I was on a 4-party line and we each got only the rings that were meant for us. There was a "ring decoder" outside the house which apparently took care of the "address recognition". One caveat (no explanation offered) is that I couldn't get touch-tone service with the party line. Telco said it would mess up the other people on the party line. ------- Of all the things I've lost, I miss my mind the most. Michael L. Begeman Microelectronics and Computer Technology Corp Software Technology Program Austin (where the sun always shines) Texas uucp: {ihnp4, seismo, harvard, gatech, pyramid}!ut-sally!im4u!milano!begeman arpa: begeman@mcc.ARPA
eric@chronon.UUCP (Eric Black) (03/12/86)
>> For party lines with two parties this means nobody gets >> a ring meant for the other party. If there are more than two parties >> on the line, the long-short-count-'em codes for rings must be used. > >Not quite true. For my first 3 years in my farmhouse, I was on a 4-party >line and we each got only the rings that were meant for us. There was a >"ring decoder" outside the house which apparently took care of the "address >recognition". One caveat (no explanation offered) is that I couldn't get >touch-tone service with the party line. Telco said it would mess up the >other people on the party line. >------- > Of all the things I've lost, I miss my mind the most. > >Michael L. Begeman Microelectronics and Computer Technology Corp >Software Technology Program Austin (where the sun always shines) Texas > >uucp: {ihnp4, seismo, harvard, gatech, pyramid}!ut-sally!im4u!milano!begeman >arpa: begeman@mcc.ARPA I greatly simplified the discussion to explain why more than 2 wires could be needed. There are several methods of selective ringing, ranging from the bridged ringer scheme using ground that I described to frequency- selective ringers (the bell itself is physically constructed so as to resonate at 20, 30, 50, 60 (or whatever) cps and AC of the appropriate frequency is used from the CO (Central Office). On rural subscriber loops (several customers on the end of a long pair of wires) in recent years has been implemented a method which all of us high-tech-types would love -- a small number of talk lines, and a digital control channel from the CO talking to a "bathtub" out in the boonies; the talk circuits are assigned as needed, and the remote bathtub connects each subscriber to the appropriate talk circuit to get to the CO (what's that you say? Sounds like a mini PBX? How 'bout that!). Anyway, for those of us living out in the middle of nowhere (I myself am on the edge of nowhere, out in the redwoods), the high cost of copper has made service from TPC somewhat of an on-again, off-again hassle. I am ecstatic to see the economic incentive for TPC to use party lines going away with improving technology. But as the recent rains have pointed out, we're still a small number of customers on the end of a long wire, and whenever we have trouble it takes a while for TPC to take care of it (they're busy fixing the break that has 10,000 customers disconnected, why should they hurry to get 25 back up?). -- Eric Black "Garbage In, Gospel Out" UUCP: {sun,pyramid,hplabs,amdcad}!chronon!eric VOICE: (415) 941-0403 US SNAIL: Chronon Computer Corp. 2570 El Camino Real W. Suite 206 Mountain View, CA 94040