A form of cable used to carry electric signals. An electric circuit must always contain an outward and a return path. For high-frequency signals, the outward and return paths consist of conducting wires that must be kept close together so that the outward current in one conductor is balanced by the corresponding inward current in the other, thus reducing the amount of energy lost by radiation. This is achieved in twisted-pair cabling by twisting the two wires together. The resulting pair of wires may either be placed inside an outer conducting screen to give a shielded twisted pair (STP), or left uncovered as an unshielded twisted pair (UTP); the screen of an STP provides additional isolation from external sources of electric interference, and is usually formed from an interwoven fine wire mesh. Many pairs can be further twisted together.
Much of the cabling installed within buildings to provide local loops for speech and low-speed data traffic is in the form of twisted pairs. There is emphasis on providing equipment capable of signaling in the gigabit range over distances of up to 100 meters over these cabling installations.