Flag signals

Flag signals allowed communication at a distance before the invention of radio and are still used especially in connection with ships.

Flaghoist is also used in boat racing, to warn of impending severe weather, and other specialized applications.

[3][better source needed] In the 1850s, U.S. Army Major Albert J. Myer, a surgeon by training, developed a system using left or right movements of a flag (or torch or lantern at night).

More mobile than previous means of optical telegraphy, as it only required one flag, this code was used extensively by Signal Corps troops on both sides in the American Civil War.

[6]) In this code, alphabet letters were equated with three positions of a single flag, disk, or light.

[7] The disks were 12 to 18 inches (30 to 46 cm) in diameter and were made of metal or wood frames with canvas surfaces.

A second "foot torch" was placed on the ground before the signalman as a fixed point of reference, making it easier for the recipient to follow the lantern's movements.

The first motion was initiated by bringing the device downward on the signalman's right side and then quickly returning it to its upright position.

A typical US Signal Corps guidon features wig-wag flags