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Coaxial cable is a type of cable for high bandwidth data transmission use that typically consists of a single copper wire that is surrounded by a layer of insulation and then by a grounded shield of braided wire or an extruded metal tube. The whole thing is usually wrapped in another layer of insulation and, finally, in an outer protective layer. The grounded metal tube or braided wire shield minimizes electrical interference and radio frequency interference (RFI) and results in a much greater bandwidth (i.e., data transmission capacity) than does conventional copper wire cable (but less than optical fiber cable). The metal tube type has a greater data transmission capacity but is rigid and thus is used only for specials situations; the braided type is much more flexible and easier to use. Connections to the ends of coaxial cables are usually made with specially designed RF (radio frequency) connectors. In the case of computer networks, BNC (Bayonet Niell-Concelman) RF connectors are used. Coaxial cable is commonly used by cable television companies to transport television broadcast signals into customer premises and by consumers to connect television receivers to external antennas. Short coaxial cables are also employed to connect home video equipment and in ham radio systems. Coaxial cable was formerly also widely used in local area networks (LANs). However, now most LANs use twisted pair wiring, optical fiber cable and radio waves because of greater ease of use, lower cost and/or greater capacity. Coaxial cable takes its name from the fact that both conductors (i.e., the central copper wire and the outer metal shield) share the same axis. It is often referred to by those in the electronics industry as coax. Although apparently invented in the latter part of the nineteenth century, the first modern coaxial cable was developed by Bell Labs, the research and development arm of the AT&T telecommunications monopoly, and patented in 1929. Created October 22, 2005. |