Telephone Cable

Telephone Cable

Twisted pair cabling is a type of wiring in which two conductors (the forward and return conductors of a single circuit) are twisted together for the purposes of cancelling out electromagnetic interference (EMI) from external sources.

In contrast to FTP (foiled twisted pair) and STP (shielded twisted pair) cabling, UTP (unshielded twisted pair) cable is not surrounded by any shielding. It is the primary wire type for telephone usage and is very common for computer networking, especially as patch cables or temporary network connections due to the high flexibility of the cables.


Most telephone wires are one or more twisted pairs of copper wire. The most common type is the 4-strand (2 twisted pair). This consists of red and green wires, which make a pair, and yellow and black wires, which make the other pair. One telephone line needs only 2 wires. Therefore it follows that a 4-strand wire can carry 2 separate phone lines. The twisting keeps the lines from interfering with each other.

There are 2 types of common modular plugs, the RJ-11 and the RJ-14. The most common is the RJ-11 which uses only 2 of the wires in a 4 (or more) strand wire. This is the same kind of plug that you use to plug your telephone into the wall. This is a 1-line plug. The RJ-14 uses 4 wires and is used to handle 2 lines, or 2-line phones.