The Characteristics of a UTP Cable

by Vladimir Khavkine

The unshielded twisted pair, or UTP, cable is the most common type of cable used in computer networking. It consists of multiple pairs of wires arranged in a certain order. As its name suggests, UTP cables are not electrically shielded and may be prone to electrical or radio interferences if used in certain environments.

Physical Characteristics

UTP cables use eight wires grouped in four pairs, each composed of a solid-colored wire and a stripped wire. Each wire is twisted a certain number of times to minimize interferences with the other pairs. A higher number of twists per inch results in a higher data transmission. The Electronic Industry Association and Telecommunication Industry Association have established six speed standards for UTP cables, with category 1 cables being the slowest and category 6 cables the fastest.

Performance

The category of a UTP cable has a high impact on its usage range. Category 1 cables have a speed of 1 Megabit per second, or Mbps, and can only be used in telephony. Category 2, 3 and 4 cables are used in telephony and low-speed networks. Category 5 cables have a speed of 100 Mbps in a two-pair configuration, known as 100BaseT Ethernet, and 1,000 Mbps if all 4 pairs are used, such as in Gigabit Ethernet. Category 6 wires are capable of speeds up to 10,000 Mbps. Category 5 cables are the most used in regular networks, while category 6 cables are more specific to high-speed networks between servers.

Uses

UTP cables use RJ-45 connectors, a larger version of a telephony connector. The order of the wires in the connector varies depending on the use of the cable. Two types of wiring exist: straight and crossover. Straight wiring is used to connect different types of devices, such as computers and switches. In a straight-wiring configuration, both connectors have the same wiring arrangement at both ends, known as T568B. Crossover cables are used to connect devices of the same type together, such as computer-to-computer or switch-to-switch, and have one end wired in T568B configuration and the other end in a similar configuration but with two reversed pairs. This configuration is known as T568A.

Limitations

The maximum length of a single segment of UTP cable should not exceed 295 feet to avoid data loss. In addition, do not use UTP cables in environments with high electrical or radio interference potential. Shielded twisted pair, or STP, cables are recommended for such environments.

About the Author

Vladimir Khavkine has been writing since 1971. He has written for various online publications. Khavkine has a Doctor of Philosophy degree in mathematics and physics from the USSR Academy of Sciences.

Photo Credits

  • photo_camera Jupiterimages/Polka Dot/Getty Images