Originally posted by n0mel:
search on google for how phones work. You'll see that only two wires are used, tip and ring. the other two (yellow and black) are used for additional lines, etc. so, to answer your question both. the two wires are used for sending and recieving the signals.
Uhh... In ALL twisted pair cables, phone or otherwise, each pair consists of a tip wire and a ring wire. If we're talking about two-pair phone wire, then there is two tips, and two rings: one for each pair.