Twisted pair - Definition and Overview

25 Pair Color Code Chart

10BASE-T UTP Cable

Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. The number of twists per metre make up part of the specification for a given type of cable. The greater the number of twists, the more crosstalk is reduced.

Shielded Twisted Pair (STP) has an outer conductive braided casing similar to coaxial cable and theoretically offers the best protection from interference. It was commonly used for token ring networks.

Unshielded Twisted Pair (UTP) is not surrounded by shielding. It is the primary wire type for telephone usage and is very common for computer networking.

UTP is standardized into various categories by number, which indicate signal integrity attributes. Category 5 cable is commonly used for Ethernet with 10BASE-T or 100BASE-TX.

In telephone applications, UTP is often grouped into sets of 25 pairs according to a standard 25-pair color code originally developed by AT&T. A typical subset of these colors (white/blue, blue/white, white/orange, orange/white) shows up in most UTP cables.

See also

• Registered jack
• EIA/TIA-568A
• EIA/TIA-568B