Twisted Pair Cable
Twisted pair cable consists of two insulated copper wires each about 1 mm thick arranged in a regular spiral pattern. The wires are twisted together to reduce the electrical interference from similar pairs which are closely by. Typically a number of pairs are bundled together in a cable by wrapping the pairs in protective shield. A wire pair constructions it communication link. Unshielded twisted pair (UTP) is commonly used for compute network within a building that is for LAN data rate for LAN using twisted pair today range from 10Mbps to 1 Gbps. The data rates can be achieved depend on the thickness of the wire and the distance between transmitter and receiver. The least expensive and most commonly used guided transmission medium is twisted pair copper wire. For over a hundred years it has been used by telephone networks. In fact more than 99 percent of the wired connections from the telephone handset to the local telephone switch use twisted pair copper wire. Most of us have seen twisted pair at our homes and work environments.
The most common twisted pair cable used in communication is refereed to as unshielded twisted pair(UTP). IBM has also produced a version of twisted pair cable for its use called shielded twisted pair cable(STP). STP cable has metal foil of braided mesh covering that encase each pair of insulated conductors. Although casing improves the quality of cable by preventing the penetration of noise or cross talk it is bulkier and more expensive figure 2.8 shows the difference between UTP and STP.
The electronic industries association(EIA) has developed standard to classify unshielded twisted pair cable into seven categories. Categories are determined by cable quality with 1 at lowest 5 UTP can achieve data rates of 100Mbps for distances up to few hundred meters. Even higher data transfer rates are possible over shorter distance.
Twisted pair cables are used in telephone lines to provide different voice and data channels. The local loop is that line which connects and subscribes to the central telephone office commonly.