Bill: I did outside plant in the Army in 1978, so I got a lot of exposure to old pole terminals. What I always couldn't understand was that the spare pair was there in the stub, but the terminal still only had 25 pairs and was epoxy-sealed. Where did that extra pair go?
As for the T-screened cable, the extra pairs are provided (one for each 25 pair binder) to provide a talk pair outside of the screened (shield) compartment.
Now, the 26th pair in inside wiring came in handy every once in a while for that fax line when you were afraid to touch that screw-terminal block that had half a dozen two-line phones in five different offices working from it. That nice rolled-up pair sure looked nice.
