semaphore machine in Paris. The 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. A precursor of the electrical telegraph, they were far
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."
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