twistedpair

Twisted pair is a type of electrical cabling in which two insulated copper conductors are twisted together along the length of the cable. The twisting reduces electromagnetic interference from external sources and from adjacent pairs, and enables balanced, differential signaling. It is widely used in telephone networks and data communications, including most Ethernet networks.

Construction typically falls into unshielded twisted pair (UTP) and shielded twisted pair (STP). UTP has no shielding, relying on twists and differential signaling for noise rejection, while STP adds shielding around one or more pairs to further suppress interference. Cables use a protective outer jacket, commonly PVC or low-smoke compounds, and conductors are usually relatively thin (for example, AWG 24 to AWG 26).

Standards and performance are organized by category, such as Cat3, Cat5e, Cat6, Cat6a, Cat7 and Cat8. Higher categories provide greater bandwidth and longer effective transmission distances. Cat5e supports up to about 1 Gbps at frequencies around 100 MHz. Cat6 improves crosstalk handling and bandwidth, enabling 1 Gbps at 100 m and up to 10 Gbps for shorter runs. Cat6a supports 10 Gbps at 100 m. Cat7 and Cat8 offer higher frequencies and data rates for specialized applications, with Cat8 designed for very high-speed short-reach links.

Applications include Ethernet local area networks (LANs) using RJ-45 connectors, as well as traditional telephone systems and various industrial control networks. Twisted pair remains a low-cost, flexible, and widely deployed solution, though its performance is limited by distance and data rate compared with fiber.