CABLE

in electrical and electronic systems, a conductor or group of conductors for transmitting electric power or telecommunication signals from one place to another. Electric communication cables transmit voice messages, computer data, and visual images via electrical signals to telephones, wired radios, computers, teleprinters, facsimile machines, and televisions. There is no clear distinction between an electric wire and an electric cable. Usually the former refers to a single, solid metallic conductor, with or without insulation, while the latter refers to a stranded conductor or to an assembly of insulated conductors. With fibre-optic cables, made of flexible fibres of glass and plastic, electrical signals are converted to light pulses for the transmission of audio, video, and computer data. in engineering, either an assemblage of three or more ropes twisted together for extra strength or a rope made by twisting together several strands of metal wire. This article deals with wire rope. For rope made from synthetic or natural organic fibres, see rope. The first successful stranded iron wire rope was developed in 183134 by Wilhelm Albert, a mining official of Clausthal in the Harz Mountains in Saxony. Even when first tried for hauling and hoisting in his mine, it proved so superior to hemp rope in serviceability and cost that its use soon became widespread in European mining. This stranded wire rope consisted of individual wires twisted about a hemp rope core to form the strand, six such strands then being twisted about a larger hemp rope core in reverse direction to form the rope. Prior to this, wire rope had already been made in the form of a selvage cablea bundle of individual wires stretched out into a long length and arranged parallel to one another, then bound together and covered with tarred hemp yarns. High-tensile steel wire was introduced during the 1880s, and steel is now the predominant metal used for wire rope. The manufacture of wire rope is similar to making rope from natural yarns or synthetic filaments. The individual wires are first twisted into strands; six strands (usually), twisted about a core rope, are then laid into the rope. The cores are cord or rope structures made of steel wires; sisal, manila, henequen, jute, or hemp fibres; or polypropylene monofilaments. The function of the core is to provide a firm cushion for positioning the wires in the strands, to maintain a firm rope structure, and to provide some internal lubrication when bending stresses are involved. Most wire ropes are used in hoisting and hauling operations and in machinery for these purposes, such as cranes, power shovels, elevators, mine hoists, and so on. A flexible rope structure to cope with fast movement and bending stresses is required for most such uses. In other uses, such as support guys and stays, this property is not so much a consideration. Selvage cables composed of parallel wires are ideally suited for the main cables of a suspension bridge (q.v.). Marine ropes are used for rigging, mooring, and towing.