Cable

Cable

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Cable, George Washington, 1844-1925, American author, b. New Orleans. He is remembered primarily for his early sketches and novels of creole life, which established his reputation as an important local-color writer. Cable served as a Confederate soldier in the Civil War and afterward was a writer and reporter for the New Orleans Picayune. His short stories of New Orleans culture began to appear in Scribner's Monthly in 1873; they were collected and published as Old Creole Days (1879). Among his novels are The Grandissimes (1880), Madame Delphine (1881), Dr. Sevier (1884), and Gideon's Band (1914). Cable's works depict the picturesque life of creoles in antebellum Louisiana with charm and freshness. Discernible in some of them is the author's moral opposition to slavery and class distinction. After 1884, Cable lived in Northampton, Mass. His later works, notably the essays collected in The Silent South (1885) and The Negro Question (1890), reveal his concern with social evils, particularly with the betrayal of the freed African American slaves.

See his letters, ed. by L. L. Leffingwell (1928, repr. 1967); biography by L. D. Rubin (1969); study by P. C. Butcher (1959).

cable, originally wire cordage of great strength or heavy metal chain used for hauling, towing, supporting the roadway of a suspension bridge, or securing a large ship to its anchor or mooring. Today a cable often refers to a line used for the transmission of electrical signals. One type of electric cable consists of a core protected by twisted wire strands and suitably insulated, especially when it is used to cross oceans undersea; a message transmitted by cable is known as a cablegram or cable. France and England were first successfully connected by submarine telegraphic cable in 1845. The first permanent transatlantic cable was laid in 1866 by Cyrus West Field, although demonstrations of its possibility had been made in 1858. The first telephone message was transmitted from New York to Philadelphia in 1936; the first transatlantic telephone cable was laid in 1956.

The coaxial cable, which is virtually immune to external interference, consists of two concentric conductors separated by an insulator; the current in the inner conductor draws the current in the outer conductor toward the center rather than letting it dissipate outwards. Because they can carry a large number of signals simultaneously, coaxial cables are also used in cable television systems. The newest form of cable is the fiber-optic cable, developed in the 1970s. Instead of a copper conductor, a silica glass fiber carries digitized signals as pulses of light.

The insulated wire that conducts electricity from generator to consumer is also called a cable; it often contains multiple conductors and must be of sufficient gauge to carry large currents. Its insulation must withstand high voltages.

System that distributes television signals by means of coaxial or fibre-optic cables. Cable television systems originated in the U.S. in the late 1940s to improve reception in remote and hilly areas, where broadcast signals were weak. In the 1960s they were introduced in large metropolitan areas where reception is sometimes degraded by reflection of signals from tall buildings. Since the mid-1970s there has been a proliferation of cable systems that offer special services and which generally charge a monthly fee. Besides providing high-quality signals, some systems can deliver hundreds of channels. Another feature increasingly offered by cable operators is two-way, interactive communication by which viewers can, for example, participate in public-opinion polls as well as connect to the Internet. Cable operators are also involved in the development of video compression, digital transmission, and high-definition television.

Learn more about cable television with a free trial on Britannica.com.

A cable is one or more wires or optical fibers bound together, typically in a common protective jacket or sheath. The individual wires or fibers inside the jacket may be covered or insulated. Combination cables may contain both electrical wires and optical fibers. Electrical wire is usually copper because of its excellent conductivity, but aluminium is sometimes used because it is lighter or costs less.

Construction

Electrical cables may be made flexible by stranding the wires. In this process, smaller individual wires are twisted or braided together to produce larger wires that are more flexible than solid wires of similar size. Bunching small wires before concentric stranding adds the most flexibility. A thin coat of a specific material (usually tin-which improved striping of rubber, or for low friction of moving conductors, but it could be silver, gold and another materials and of course the wire can be bare - with no coating material) on the individual wires. Tight lays during stranding makes the cable extensible (CBA - as in telephone handset cords).

Bundling the conductors and eliminating multi-layers ensures a uniform bend radius across each conductor. Pulling and compressing forces balance one another around the high-tensile center cord that provides the necessary inner stability. As a result the cable core remains stable even under maximum bending stress.

Cables can be securely fastened and organized, such as using cable trees with the aid of cable ties or cable lacing. Continuous-flex or flexible cables used in moving applications within cable carriers can be secured using strain relief devices or cable ties. Copper corrodes easily and so should be layered with Lacquer.

History

In the 19th century and early 20th century, cable was often insulated using cloth, rubber and even paper. Plastic materials are generally used today, except for high reliability power cables. There are four types of plastic insulation used in telecommunications cables today: solid, cellular, foam skin and skin-foam-skin.

Fire protection

Cables as a fire hazard

In construction, sometimes the cable jacketing is seen as a potential source of fuel for a fire. To limit the spread of fire along cable jacketing, one may use cable coating materials or one may use cables with jacketing that is inherently fire retardant. Teck cable or metal clad cables, may have exterior organic jacketing, which is often stripped off by electricians in order to reduce the fuel source for accidental fires. In Europe in particular, it is often customary to place inorganic wraps and boxes around cables in order to safeguard the adjacent areas from the potential fire threat associated with unprotected cable jacketing.

Interference protection

In applications powering sensitive electronics, keeping unwanted EMI/RFI from entering circuits is important. This can be accomplished passively with shielding along the length of the cable or by running the cable in an enclosure separate from any other wires which may induct noise. It can also be actively achieved by use of a choke designed to restrict the cables' ability to conduct certain frequencies.

Types of cable

Cables can be sorted into several categories and types. Generally it can by sorted into two main groups, structural and informatic.

Application

Cable type

Basic cable types are as follows:

Basic

Construction

Based on construction and cable properties it can be sorted into the following:

Special

Market Information

Cable manufacturers

The leading global producers of wire and cable include (in no particular order): Clynder Cables, Canare, Draka, General Cable, Belden, Nexans, India, igus, Sumitomo Electric Industries, Furukawa Electric, Hitachi Cable, Southwire, Marmon Group, LS Cable, Leoni, Fujikura, Tyco, Prysmian, Lapp, Wonderful Hi-Tech, Walsin Lihwa and Wilms Group, and Jainson Cables - India.

See also

External links

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