Tuesday, October 15, 2013

Code 26 : Semaphore

Sempahore is similar to Morse code in that each letter of a message is translated into another form to allow it to be more easily communicated. While Morse code is used to send messages electronically over a telegraph line, semaphore is used to visually communicate information over long distances. To use semaphore, an operator holds a flag or lighted wand in each hand. The operator extends their arms to the correct position and pauses for each letter of the message. "Attention" is the only signal that involves movement and the "rest" position is the only time when the flags should cross.


The Semaphore flag signaling system is an alphabet signalling system based on the waving of a pair of hand-held flags in a particular pattern.
flag image The flags are usually square, red and yellow, divided diagonaly with the red portion in the upper hoist.
The flags are held, arms extended, in various positions representing each of the letters of the alphabet. The pattern resembles a clock face divided into eight positions: up, down, out, high, low, for each of the left and right hands (LH and RH) six letters require the hand to be brought across the body so that both flags are on the same side.
flag image Flag positions in Semaphore
One way to visualize the semaphore alphabet is in terms of circles:
  • first circle: A, B, C, D, E, F, G;
  • second circle: H, I, K, L, M, N (omitting J);
  • third circle: O, P, Q, R, S;
  • fourth circle: T, U, Y and 'annul';
  • fifth circle: 'numeric', J (or 'alphabetic'), V;
  • sixth circle: W, X;
  • seventh circle: Z
In ther first circle, the letters A to C are made with the right arm, and E to G with the left, and D with either as convenient. In the second circle, the right arm is kept still at the letter A position and the left arm makes the movements; similarly in the remaining circles, the right arm remains fixed while the left arm moves. The arms are kept straight when changing from one position to another.

The Semaphore Alphabet

flag image A and 1 (LH down RH low) flag image B and 2 (LH down; RH out)
flag image C and 3 (LH down; RH high)
flag image D and 4 (LH down; RH up - or LH up; RH down)
flag image E and 5 (LH high; RH down)
flag image F and 6 (LH out; RH down)
flag image G and 7 (LH low; RH down)
flag image H and 8 (LH across low; RH out)
flag image I and 9 (LH across low; RH up)
flag image J and 'alphabetic' (LH out ; RH up)
flag image K and 0 zero (LH up; RH low)
flag image L (LH high; RH low)
flag image M (LH out; RH low)
flag image N (LH low; RH low)
flag image O (LH across high; RH out)
flag image P (LH up; RH out)
flag image Q (LH high; RH out)
flag image R (LH out; RH out)
flag image S (LH low; RH out)
flag image T (LH up; RH high)
flag image U (LH high; RH high)
flag image V (LH low; RH up)
flag image W (LH out; RH across high)
flag image X (LH low; RH across high)
flag image Y (LH out; RH high)
flag image Z (LH out; RH across low)
flag image Numerical sign (LH high; RH up)
flag image Annul sign (LH low; RH high)
flag image Error (LH and RH raised and lowered together)


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