You have 50 pairs, how many phones? As telemarv suggested, using two or even three pairs for each phone will give you more power, remember the power to run the phone has to go that far on 24 gage wire as well as the data. More copper = more power.

I don't think anyone who wasn't an old timer would realize the scope of the job. People who just read a book and take a test don't get this information and don't offer it to you.

As everyone said, get an expert. If there is a Volt contractor in your area, they could do it. You could talk to some of the techs at the local AT&T or Verizon or whoever central office and see if they would come over off hours and do this.

My suggestion would be to use as many pairs as you can, ground the rest, and have solid earth grounds on both ends. Everyone above is giving you solid advice for free and it is worth much more than that.

Print this out and give it to Volt or a tech working out the central office or an independent.

THE Bracha, old blond specialist in Rube Goldberg solutions.