More information is available on the website www.encyclopedia4u.com/s/semaphore-communication-.html

The semaphore system we use today uses flags, usually square and divided diagonally into a red and a yellow section with the red in the uppermost triangle.

The signaler, with arms extended, holds the flags in various positions to represent the different letters of the alphabet. There are eight positions for each flag (up, down, out high, low for each of the left and right hands (LH and RH)). For six of the positions (letters H, I, O, W, X, Z see below) the signaler is required to hold one or other of the flags across the body so that both flags are on the same side. The flags, though, are never both in the same position. Although the flags have two different patterns, these are not relevant to the signaling - flags of one color could be used with the same result.

The full Semaphore alphabet is shown below.