Semaphore

Semaphore is a name applied to the mechanism of signaling employed for telegraphing purposes prior to the discovery of the electric telegraph. It was invented in 1767 by Richard Edgeworth, but first extensively used by the French in 1794, and afterwards adopted by the Admiralty in England. It consisted at first of six shutters set in two rotating circular frames, which, by opening and shutting in various ways, were capable of conveying sixty-three distinct signals. These were raised on the tops of wooden towers erected on hills. Later a different form was adopted consisting of a mast and two arms worked by winches. The speed at which messages could be transmitted was very great. Thus a message could be sent from London to Portsmouth and an answer be received all within 45 seconds. Later, the railway signal used a form of semaphore.

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