Pair

A 'Pair' is two or something e.g. an electrical pair. To transmit a signal (analogue or digital), a pair of wires is required, so that the voltage difference between the wires can be compared and used as information. Telecom wires are often referred to as "pairs", meaning two wires that together convey an electrical signal between endpoints.

Telecom pair problems may sometimes be diagnosed using a PSD.