Semaphore line

1 ANSWERS

1. Brett
   

   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. These systems were popular in the late 18th - early 19th century. In modern usage, "semaphore line" and "optical telegraph" may refer to a relay system using flag semaphore.
   
   Semaphore lines were the prototype of the electrical telegraph. They were faster than post riders for bringing a message over long distances, but far more expensive and less private than the electrical telegraph lines which would replace them. 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.

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