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.