The semaphore was a mechanical contrivance in the late 18th and 19th centuries that served to transmit messages within visual range (Optical telegraphy). It usually consisted of a mast with movable (transverse) arms, controlled by levers and cables, whose positions represented a character set. Aided by the use of telescopes, the positioning of the semaphores as a chain of relay stations – preferably on heights – made it possible to cover substantial distances in almost no time

The techniques of signaling practiced since antiquity (smoke, light, fire) were limited to rud…