The twisting of the wires around each other helps to reduce unwanted signals being induced into the wires. It is used for telephone wiring inside buildings, as telephone cables which link customer houses and buildings to telephone switching exchanges, and for implementing local area networks. There became a need to inter-connect telephone centers in different towns together. Hence the introduction of coaxial cable. Till recently, coaxial cable was extensively used to support toll traffic and long distance links.
Coaxial cable is a two wire conductor with a larger bandwidth than twisted pair cable.
It is used in television, radio, and Ethernet LANs. In voice communication systems, each coaxial cable supports about 60 speech channels. It has a single core, with an outer conductor which acts as a shield. The signal is transmitted on the inner core. The inner core and the outer shield are separated by an insulator, either plastic or mica.