MAP@lcs.mit.edu (Michael A. Patton) (12/08/89)
From: John Higdon <john@zygot.ati.com> Date: 2 Dec 89 21:21:29 GMT >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. You are wrong about this NEVER working, I had such an installation in service for many years with a run of 4 floors vertical plus some horizontal distance. I used this "extra" line for 212-style dialup data and had fewer problems than any other line I've used with 212 modems. However, a warning (somewhat moderated) is still in order. This "kludge" was done only on the fifth "installation" trip---the first to feature a repeat performer, by the way. On several of the earlier trips many different options were explored, including fire-rated drop cable through an interior "well" in the building and many others. I had talked with the installation and repair supervisor literally dozens of times (we were getting to be good buddies, too bad he's not there any more :-). After all this and another while on this call scouting more possibilities, the three of us decided that the only way that could possibly work was to use my "third wire" and the "third wire" from either the apartment above or below me, we knocked on doors and one of the neighbors was home. I got it installed this way with the implied agreement between me and the supervisor that I wouldn't complain if it was "noisy" (I actually got the impression that he attached a notation of "Contact <his name>" for all reports concerning this line before any action). It turned out to be a perfectly fine connection, never a single problem with errors. I would caution however that it really shouldn't have worked, as John points out. In fact I was somewhat agast at it actually being BETTER than the original line had been, I'd expected to need to use the original to get data connections at all and start telling all my callers to use the other phone. We only got to this after exploring MANY other options with the landord and the phone company. I recommend exploring ALL other options first. The phone company was ready to declare it "uninstallable" without this, in fact if I hadn't shown such a wide knowledge of TPC during all the previous dealings with installers and the supervisor they probably wouldn't even have suggested it. I forget why subscriber carrier wasn't an option in my case, but it was brought up. If possible, I would guess this has a better likelihood of working than picking two random wires as a "pair".