Semaphore line
A semaphore line is an installation used to send optical signals. It is also known as optical telegraph. Common system include signal towers with special installations on them or hand-held flags. The meaning of the signal is determined by the position of the elements, for example the flags. The signal can be read when it is in a stable position. In modern usage, it refers to signalling with a set of flags.
Signal towers came before the electric telegraph. They were faster than sending out post riders with the information.
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Diagram of person holding 2 semaphore flags as letter "P"
Characters[change]
The following semaphore characters are presented as one would face the flagman:
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Rest / Space
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Numerals
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Error
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Cancel
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A / 1
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B / 2
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C / 3
Acknowledge -
D / 4
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E / 5
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F / 6
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G / 7
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H / 8
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I / 9
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J
Letters -
K / 0
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L
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M
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N
Negative -
O
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P
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Q
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R
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S
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T
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U
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V
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W
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X
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Y
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Z
