Semaphore Telegraph

a system for visual transmission of messages by means of a semaphore alphabet. The system was widely used in the first half of the 19th century. The first semaphore telegraph was built in 1794 between Paris and Lille, a distance of 225 km, by the French brothers C. Chappé and I. Chappé. The transmitting equipment consisted of movable arms and was mounted on towers. A semaphore telegraph line consisted of a chain of towers spaced at distances of direct visibility. Messages were transmitted from tower to tower and therefore required considerable time. The longest semaphore telegraph line in the world operated from 1839 to 1854 between St. Petersburg and Warsaw, a distance of 1,200 km; transmission of a signal from one end to the other took 15 minutes.