Optical telegraph

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The optical telegraphs preceded the electrical telegraph. It was faster than riding couriers for bringing a message over long distances. Types of optical telegraphs are the semaphore, ship flags, smoke signals, and beacons. The distance that an optical telegraph can bridge is limited by geography, the shape of the earth, and the sharpness of the human eye. In practical use, most optical telegraphs used relay leagues to bridge longer distances.

There was in France at the end of the 18th century a complete and working installation of optical telegraph. During the Revolutionary period, a French inventor, Claude Chappe (1763-1805), convinced the Deputies to set up a huge network between major cities. It was used for army and national communications till the 1850s.

Throughout Chinese history, smoke signals were used as communication tool during war time. Until these days, the Chinese phrase (烽火 feng1 huo3, fire signals) is still used as a synonym for war.