title: Telephone line
context: The vast majority of houses in the U.S. are wired with 6-position modular jacks with four conductors (6P4C) wired to the house's junction box with copper wires.  Those wires may be connected back to two telephone overhead lines at the local telephone exchange, thus making those jacks RJ14 jacks. More often, only two of the wires are connected to the exchange as one telephone line, and the others are unconnected.  In that case, the jacks in the house are RJ11.
question: What material is used for telephone wires?
answers: copper wires