The Prussian Semaphore System was a telegraphic communications system used between Berlin and the Rhine Province from 1832 to 1849. It could transmit administrative and military messages by optical signal over a distance of nearly 550 kilometres (340 mi). The telegraph line comprised 62 stations each furnished with a signal mast with six cable-operated arms. The stations were equipped with telescopes that operators used to copy coded messages and forward them to the next station. Three dispatch departments (telegraphische Expeditionen) located in Berlin, Cologne and Koblenz handled the coding and decoding of official telegrams. Although electric telegraphy made the system obsolete for military use, simplified semaphores were still used for railway signals.
At the time of construction of the Prussian semaphore system, the technology had already been known for thirty years. It was based on earlier designs by Claude Chappe and his brother which were in use in France on many telegraph lines from 1794.
A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore 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 system was invented in 1792 in France by Claude Chappe, and was popular in the late eighteenth to early nineteenth century.
They were much faster than post riders for bringing a message over long distances, and also cheaper in their long-term operating costs, once constructed. Semaphore lines were a precursor of the electrical telegraph which would replace them half a century later. The electrical telegraph would in turn be cheaper, faster, and more private. The distance that an optical telegraph can bridge is limited by geography and weather; thus, in practical use, most optical telegraphs used lines of relay stations to bridge longer distances. This also prevented the optical telegraph from crossing long expanses of water, unless a convenient island could be used for a relay station.