The word Semaphore is used in a number of contexts. It is usually used for a visual signaling apparatus that is available with flags, lights or even arms. It is also used to refer to a visual system of sending information by using two flags in each hand.
It has a very old history. Semaphore tricks have been in use since ancient times. These include, signaling to incoming or outgoing ships through lights in the light tower. Signaling to airplanes through flags etc.
The term semaphore is composed of two words: Greek word sema and phore. The word sema means sign. The second word phore means 'bearer of'. It is a combining element in words. Thus, semaphore is an apparatus that is used for signalling. It includes flags and lights. Mechanical moving of arms is also counted under this visual apparatus. These tools are generally used on railroads.
Semaphore is another visual system used to send information in alphabetic code. In this, one makes use of two flags; one flag in each hand. The signaller positions his hands in particular way. Each position corresponds to specific alphabet. When someone semaphores, he signals using a semaphore. For example: the station master semaphored the train-driver to halt the train.
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