Semaphore Flag Signalling System

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.

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 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.