Coaxial cable is a type of cable that contains two conductors—an inner one and an outer one. It is called coaxial because both conductors have the same axis (center). The outer conductor is shaped like a tube. It may be made of a flexible woven metal braid or solid metal. The inner conductor is a wire that runs through the center of the outer conductor. The conductors are separated by insulation, usually a plastic. A layer of plastic typically coats the outer conductor, insulating the cable from outside contact and protecting it from damage. Cables with outer conductors of solid metal may be uncoated. Coaxial cables range in diameter from about 1/10 inch (3 millimeters) to more than 3 inches (8 centimeters). Several small cables may be bundled together inside one large one.
Uses.
Fiber-optic cables have replaced coaxial cables for some communications applications (see Fiber optics ). But coaxial cables are still used to transmit electric power and to send communication signals to and from antennas. A coaxial cable can carry high-frequency communications signals more efficiently than other types of cables. A large-diameter coaxial cable can carry thousands of telephone conversations or hundreds of cable television signals at once. Smaller cables transfer signals to and from the antennas of communications equipment used by the military, police and fire departments, and other government and private agencies. Still smaller cables transfer signals between electronic devices used in the home and in offices.
History.
The invention of modern coaxial cable is generally credited to two American electrical engineers, Lloyd Espenschied and Herman A. Affel. Both men worked for the American Telephone and Telegraph Company (AT&T). When they patented their work in 1931, the cable was intended to be used for transmitting television signals. However, the cable was first used to transmit voice signals between New York City and Philadelphia in 1936.
See also Cable .
