We dont have T1 here but we do have 30 channel PRI, which is basicaly a 2 meg link, they normaly use 1 pair for this circuit, but if the distance is over 2 miles from exchange they use 2 pairs circuits and re-configure the modem.

But our interface to the modem is always 2 pairs

“I have not failed. I've just found 10,000 ways that won't work.”