What was a semaphore telegraph?

A semaphore telegraph is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position. The semaphore telegraph system required a series of towers to relay messages over longer distances. Practical limitations of the semaphore telegraph included weather, geography and daylight.

The first successful semaphore telegraph developed is credited to the French engineer Claude Chappe and his brothers in 1792. Chappe succeeded in covering France with a network of 556 stations stretching a total distance of 4,800 kilometres (3,000 mi). The Chappe system was used for military and national communications in France until the 1850s. The semaphore telegraph systems were successful enough that Samuel Morse initially failed to sell the electrical telegraph to the French government; however, France finally committed to replace semaphores with electric telegraphs in 1846.