The way wigwagging is done is like this: Each craft has a signal book which gives the positions of the flags and the meaning of them. These flags are usually manipulated by a signalman (see [Fig. 55]) though sometimes a mechanical apparatus called a semaphore, which has two movable arms to hold the flags, is used.
FIG. 55. SIGNALING BY MEANS OF FLAGS.
Two flags are used, one in each hand or on each arm, and each position of the flags means a letter of the alphabet, and so by showing the flags in various positions to represent different letters words are spelled out.
Another scheme that is used to signal with flags is by running, that is displaying, a number of different colored flags on a halyard. The combinations of flags—or to use the right word, permutation, which means the number of different arrangements of a few flags that are possible—are numerous and each permutation represents some word or a sea-term.
Now, you might think that it would take a couple of hundred flags of different colors to represent a message, and, further, that since there are only eight colors which can be told from each other at a distance of half a mile, signaling by colors could not be done.
But this is what you think, and not what you have figured out, for if you have eight flags of different colors and display them, four at a time, on the signal halyard you can make the surprising number of 1680 permutations; and this, you will allow, is enough to say anything that you may have to say.
Although a code book is found in every signalman’s outfit, he is a chap who knows all the signals by heart and can send and receive flag messages almost as fast as you can write down the words.
The Flashlight System.—There are two methods used for sending signals at night over short distances, and both are done by means of light; named, these are (1) the colored light system, and (2) the searchlight system.