Telegraph

Telegraph, electrical apparatus for sending coded messages. The term was first applied in the 18th century to Claude Chappe's semaphore. Experiments began on electric telegraphs after the discovery (1819) that a magnetic needle was deflected by a current in a nearby wire. In 1837 W.F. Cooke and Charles Wheatstone patented a system using six wires and five pointers that moved in pairs to indicate letters in a diamond-shaped array. It was used on English railroads. In the same year Samuel Morse, in partnership with Alfred Vail and helped by Joseph Henry, patented a telegraph system using Morse code in the United States. The first intercity line was inaugurated in 1884. In 1858 Wheatstone invented a high-speed automatic Morse telegraph, using punched paper tape in transmission; the telex system, using teletypewriters, is now most popular. In 1872 Jean-Maurice-Emil Baudot invented a multiplexing system for sharing the time on each transmission line between several operators. Telegraph signals are now transmitted not only by wires and land lines, but also by submarine cables and radio.

See also: Morse, Samuel Finley Breese; Wheatstone, Sir Charles.