Semaphore line Optical communication

a replica of 1 of chappe s semaphore towers (18th century).

a semaphore telegraph , called semaphore line , optical telegraph , shutter telegraph chain , chappe telegraph , or napoleonic semaphore , system used conveying information means of visual signals, using towers pivoting arms or shutters, known blades or paddles. information encoded position of mechanical elements; read when shutter in fixed position.

semaphore lines precursor of electrical telegraph. far faster post riders conveying message on long distances, far more expensive , less private electrical telegraph lines later replace them. maximum distance pair of semaphore telegraph stations can bridge limited geography, weather , availability of light; thus, in practical use, optical telegraphs used lines of relay stations bridge longer distances. each relay station require complement of skilled operator-observers convey messages , forth across line.

the modern design of semaphores first foreseen british polymath robert hooke, first gave vivid , comprehensive outline of visual telegraphy in 1684 submission royal society. proposal (which motivated military concerns following battle of vienna preceding year) not put practice during lifetime.

the first operational optical semaphore line arrived in 1792, created french engineer claude chappe , brothers, succeeded in covering france network of 556 stations stretching total distance of 4,800 kilometres (3,000 mi). used military , national communications until 1850s.

many national services adopted signaling systems different chappe system. example, britain , sweden adopted systems of shuttered panels (in contradiction chappe brothers contention angled rods more visible). in spain, engineer agustín de betancourt developed own system adopted state. system considered many experts in europe better chappe s, in france.

these systems popular in late 18th 19th century not compete electrical telegraph, , went out of service 1880.