owens%tartarus@gargoyle.uchicago.edu (Christopher Owens) (11/30/89)
I want to bring a second phone line into my apartment, which is in a 1920's highrise in Chicago. There is no problem getting the second pair to the terminal block across the hall from my apartment, but there the fun starts. Running from the terminal block to my apartment is an old-style twisted-3 -- apparently once upon a time subscriber lines required three conductors: tip, ring, and a third line that played some role in kicking the switch gear into action. (Was sleeve extended all the way to customer premises?) From the junction box to my apartment is only a run of about 25 feet, but the twisted three shares a conduit with two other twisted threes serving two other apartments. The installer said the cable was stiff and brittle, and that there was no way to pull new cable without pulling new cable for all three apartments at once. This is estimated to be about $300 in labor. I don't feel like paying to upgrade service to apartments I don't inhabit, and the building doesn't want to pay either. Anybody have a suggestion? One thought was to use the extra wire of my three with an extra wire taken from somewhere, but there really is nowhere. I can't get to any of the other wires from my apartment. I've been told there is a way to use some kind of bridge circuit at each end of a 3-conductor wire to enable two phone lines to be run over the wire. Does anyone know about this. If they exist, where can one get them? This didn't sound like any kind of fancy multiplexing, just a bridged circuit of some kind. Would it leave me with a clean line and full bandwidth? How would it interact with a high-speed modem on one of the lines? Thank you.
John Higdon <john@zygot.ati.com> (12/03/89)
In article <telecom-v09i0542m07@chinacat.lonestar.org>, owens%tartarus@ gargoyle.uchicago.edu (Christopher Owens) writes: > I've been told there is a way to use some kind of bridge circuit at > each end of a 3-conductor wire to enable two phone lines to be run > over the wire. Does anyone know about this. If they exist, where can > one get them? This didn't sound like any kind of fancy multiplexing, > just a bridged circuit of some kind. Would it leave me with a clean > line and full bandwidth? How would it interact with a high-speed > modem on one of the lines? My earlier rantings on the subject notwithstanding, probably the most practical and reliable way to get your second service would be to use a subscriber carrier device. There is a way to phantom a third service from two pairs, but that doesn't apply here. Whatever you do, NEVER pick conductors from two different cables to serve as your "pair". This, in effect, causes your line to look like an unbalance circuit in each of the cables you have selected and there will be major crosstalk. In other words, don't take the third conductor from, say your existing service and your neighbor's service, to supply the run for your second line. Everyone will end up talking to everyone else. John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.ati.com | San Jose, CA 95150 | M o o !
toddi@gtisqr.UUCP (Todd Inch) (12/07/89)
In article <telecom-v09i0542m07@chinacat.lonestar.org> owens%tartarus@gargoyle.uchicago.edu (Christopher Owens) writes: >I want to bring a second phone line into my apartment . . . >Running from the terminal block to my apartment is an old-style >twisted-3 (conductor cable) . . . >From the junction box to my apartment is only a run of about 25 feet, >but the twisted three shares a conduit with two other twisted threes >serving two other apartments. >One thought was to use the extra wire of my three with an extra wire >taken from somewhere . . . I found out the hard way how important the "twisted pair" is: I once wired a building for phone using two "twisted-3" cables. My thought was that I wanted a total of six conductors, for up to three lines. What I really needed was a 3-pair equivalent, but at the time I didn't understand the "pair" concept. So I used one conductor from each cable to form the three pairs: {red A & red B}, {white A & white B}, {black A & black B}, where A is one twisted-3 cable and B is the other. This worked fine for the first line, but I had all the six conductor jacks installed before I connected the second line. That's when the trouble started. You could hear the conversations on the second line almost as well as you could hear your own conversation on the first, and vice-versa. Apparently, the twisting of the pair effectively sheilds it from the electromagnetic radiation of the other pairs. By not using any of the existing two twisted pairs but instead using separate twists for one wire of each line, I had created the worst-case condition, effectively creating a transformer which coupled the two lines together. The problem was especially bad because, at the time, my parents were going through a divorce and each had a separate phone line and they were sorta in separate buildings which shared some wiring. They didn't appreciate being forced to listen to each others' conversations. Anyway, if you try to use the spare conductor from your cable and the spare conductor from someone else's, you may end up with a three-way party line. It might work for only 25 feet, but I wouldn't bet on it. >I've been told there is a way to use some kind of bridge circuit at >each end of a 3-conductor wire to enable two phone lines to be run >over the wire. I once had a device on the outside of my house that allowed two different lines to somehow use the same pair to the phone company. Telco installed it and there must have been a device at the CO to run it. This was mentioned in passing here in the digest about a month ago. I'm not sure if you could convince telco to install one or not. Todd Inch, System Manager, Global Technology, Mukilteo WA (206) 742-9111 UUCP: {smart-host}!gtisqr!toddi ARPA: gtisqr!toddi@beaver.cs.washington.edu "You are the booger in the nose of my life." - My wife, to me. (Jokingly?) Disclaimer: My boss will read this while checking up on me and will disagree.