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An electrical cable is made of two or more wires running side by side and bonded, twisted, or braided together to form a single assembly, the ends of which can be connected to two devices, enabling the transfer of electrical signals from one device to the other. Cables are used for a wide range of purposes, and each must be tailored for that purpose. Cables are used extensively in electronic devices for power and signal circuits. Long-distance communication takes place over undersea cables. Power cables are used for bulk transmission of alternating and direct current power, especially using high-voltage cable. Electrical cables are extensively used in building wiring for lighting, power and control circuits permanently installed in buildings. Since all the circuit conductors required can be installed in a cable at one time, installation labor is saved compared to certain other wiring methods. The term originally referred to a nautical line of specific length where multiple ropes, each laid clockwise, are then laid together anti-clockwise and shackled to produce a strong thick line, resistant to water absorption, that was used to anchor large ships. In mechanics, cables, otherwise known as wire ropes, are used for lifting, hauling, and towing or conveying force through tension. In electrical engineering cables are used to carry electric currents. An optical cable contains one or more optical fibers in a protective jacket that supports the fibers. ==Etymology== Ropes made of multiple strands of natural fibers such as, hemp, sisal, manila, and cotton have been used for millennia for hoisting and hauling. By the 19th century, deeper mines as well as construction of larger and larger sailing ships increased demand for stronger ropes. In 1830 the Royal Navy defined a cable as three hawser laid (clockwise) ropes, each approximately 120 fathoms in length, laid anti-clockwise, tightly twisted and shackled to a resulting length of approximately 100 fathoms. The tight twists, shortened the overall length of the ropes but both strengthened the ropes and reduced the ability of the rope to absorb water making them ideal for mooring.〔(【引用サイトリンク】title=Glossary of Nautical Measures - Lengths - Hemyock Castle )〕〔International Maritime Dictionary by Rene & Kerchove, published 1961, Van Nostrand Reinheld Co.〕 Improvements to steelmaking techniques made high-quality steel available at lower cost, and so wire ropes became common in mining and other industrial applications while continuing the practice of anti-cyclical twists to strengthen them even further. By the middle of the 19th century, manufacture of large submarine telegraph cables was done using machines similar to those used for manufacture of mechanical cables. As the move from rope to wire happened, the specific length associated with a cable fell into disuse. As electricity became more and more ubiquitous the practice of using more than bare copper led to groupings of wires and various sheathing and shackling methods that resembled the mechanical cabling so the term was adopted for electrical wiring. In the 19th century and early 20th century, electrical cable was often insulated using cloth, rubber or paper. Plastic materials are generally used today, except for high-reliability power cables. The term has also come to be associated with communications because of its use in electrical communications. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cable」の詳細全文を読む スポンサード リンク
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