# Twisted Pair Cable ## What is Twisted Pair Cable Twisted pair cable is the most common type of guided transmission medium used in computer networks and telephone systems. It consists of pairs of copper wires that are twisted together along the length of the cable. The twisting of the wire pairs is not accidental but is a deliberate design feature that reduces electromagnetic interference and crosstalk. Crosstalk occurs when the signal in one wire pair interferes with the signal in an adjacent pair. By twisting the pairs, the interference from one half-twist is cancelled by the interference from the next half-twist, resulting in a net reduction in interference. ## Types of Twisted Pair Cable Unshielded Twisted Pair, abbreviated as UTP, is the most common type used in Ethernet networks and telephone systems. It relies entirely on the cancellation effect of the twisting to reduce interference and does not have any additional shielding. UTP is inexpensive, flexible, and easy to work with, making it the most widely used cable type in office networks. Shielded Twisted Pair, abbreviated as STP, adds a metallic foil or braided shield around each pair or around all the pairs together. This additional shielding provides better protection against electromagnetic interference from external sources and is used in environments with high levels of electrical interference such as near motors or fluorescent lighting. ## Cable Categories Twisted pair cables are classified into categories based on their performance characteristics. Category 3 cable supports speeds up to 10 megabits per second and was widely used for telephone and early Ethernet installations. Category 5 cable supports speeds up to 100 megabits per second. Category 5e cable is an enhanced version of Category 5 that supports gigabit speeds and reduces crosstalk. Category 6 cable supports speeds up to 10 gigabits per second over short distances and provides improved performance over Category 5e. Category 6a, Category 7, and Category 8 cables support even higher speeds and are used in data centers and high-performance network installations. ## Connectors The standard connector used with twisted pair Ethernet cables is the RJ-45 connector, which looks like a wider version of a telephone jack. The RJ-45 connector has eight pins that connect to the eight wires in a four-pair twisted pair cable. For telephone connections, the smaller RJ-11 connector is used. ## Advantages and Disadvantages Twisted pair cable is inexpensive compared to coaxial or fiber optic cable. It is flexible and easy to install and terminate. RJ-45 connectors are easy to attach to cable ends using relatively simple tools. The main disadvantages are limited bandwidth compared to fiber optic cable, susceptibility to interference in very high noise environments even with shielding, and limited transmission distance, typically a maximum of 100 meters for Ethernet without repeaters.