More expensive than twisted-pair wire, coaxial cable (also called co-ax or sbielded cable) is a high-frequency transmission cable that replaces the multiple wires of telephone lines with a single solid copper core that is thickly insulated. Coaxial cable has 80 times the transmission capacity of twisted-pair cable. The insulation is composed of a nonconductive material covered by a layer of woven wire mesh and heavy-duty rubber or plastic. Coaxial cable is similar to the cable used to connect your TV set to a cable TV service.
Coaxial cables can also be bundled together into a much larger cable. This type of communications line has become very popular because of its capacity and reduced need for signals to be refreshed. Coaxial cables are most often used as the primary communications medium for locally connected networks in which all computer communication is within a limited geographic area, such as in the same building. Computers connected by coaxial cable do no need to use modems. Coaxial cable is also used for undersea telephone lines.