Optical telegraph
OverviewEtymology and terminologyEarly designsPrevalenceAs first data networksIn popular cultureSee alsoFurther reading
An optical telegraph is a line of stations, typically towers, for the purpose of conveying textual information by means of visual signals (a form of optical communication). There are two main types of such systems: the semaphore telegraph which uses pivoted indicator arms and conveys information according to the direction the indicators point, and the shutter telegraph which uses panels that can be rotated to block or pass the
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