Semaphore flags

Type a message and each letter is drawn as the signaller holds it, as you see them facing you. The steps say where each flag goes in words. Digits are sent after the Numerals sign, a space becomes the rest position, and punctuation is left out, because semaphore has no signs for it.

Every letter is two flags held in two of eight directions: straight up, straight down, out to each side, and the four diagonals. The drawings are as you see the signaller from the front, so their right hand is on your left.

The letters fall into groups. A to G keep one flag pointing straight down while the other moves round the circle; H, I and K to N keep one flag down and to your left (J is the odd one out, used as a control sign); O to S keep one flag out to your left. With the eight directions there are 28 ways to pair two flags, enough for the 26 letters and two control signs.

To send numbers, signal Numerals first; then A to I stand for 1 to 9 and K for 0, until J, letters follow, switches back. The rest position, both flags down and crossed in front, separates words. Cancel tells the reader to ignore the last signal, and Attention, both arms waved up and down, asks for the receiver's notice before a message.

Flag semaphore began in 1866 as a hand-held version of the optical telegraph, chains of signal stations with big movable arms that Home Riggs Popham, and later Charles Pasley, had used on land. It spread through the world's navies and is still used for ship-to-ship signals during refuelling at sea, as well as by Scouts and lifeguards.

The peace symbol is semaphore too: Gerald Holtom drew it in 1958 for the Campaign for Nuclear Disarmament from the signals for N and D. The Beatles meant to spell HELP in semaphore on the cover of Help!, but the shot looked better with their arms in a meaningless pose. And RFC 4824, an April Fools' memo from 2007, describes sending internet traffic by semaphore.