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.
- Diagram of person holding 2 semaphore flags as letter "P"
Characters
The following semaphore characters are presented as one would face the flagman:
- Rest / Space
- Numerals
- Error
- Cancel
- A / 1
- B / 2
- C / 3
Acknowledge - D / 4
- E / 5
- F / 6
- G / 7
- H / 8
- I / 9
- J
Letters - K / 0
- L
- M
- N
Negative - O
- P
- Q
- R
- S
- T
- U
- V
- W
- X
- Y
- Z
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