The International code of signals (ICS) is an international system of signals and codes developed for communication between vessels about safety of navigation and so on. Signals can be sent by flaghoist, signal lamp, radiotelegraphy, radiotelephony and flag semaphore which is more interesting for us.
Initially, the meaning of the flag signal was determined only by the location of the flag. The first attempts to regulate and unify flag signals refer only to the XVII century. In 1653 the first collection of flag signals was published in Great Britain.
The meaning of the signal depended not only on the type of flag, but also on the place of its raise, as well as on the certain combination of sails or gun shots.
In 1780 it was decided to leave as signal flags only 10 of them. A little later, in 1800, Captain Home Riggs Popham composed the “Maritime Dictionary”, in which more than 2000 flag signals were decoded. In 1803, the Royal Navy received Popham’s system and the flag signals remained as a prerogative of the military.
At the beginning of the 19th century Frederic Marriyas created “System of code signals for the merchant fleet.” The system consisted of 15 flags and pennants and was used only by the British. In course of time there was a need to compile a similar system for international use. In 1887 all maritime states adopted the “International code of signals” – the expanded version of the “System of code signals for the merchant fleet”. It came into force on January 1, 1901.
In 1931 an international commission from eight countries modified the system of signals, making it more convenient. The last revision of the Code took place on April 1, 1969. Since then, the flags have also been deciphered in Cyrillic. Now the international code of signals contains 26 alphabetic flags, 10 digital and 3 substituting flags.
How it works
Signaling flags are the set of ones of different colors, shapes and markings which are used singly or in combination. They include 26 square flags which depict the letters, ten numeral pendants, one answering pendant, and three substituters or repeaters. For example, the letter ‘O’ indicates there is a man overboard, the letter ‘B’ that the ship is taking on or discharging explosives.
Only a few colors can be readily distinguished at sea. These are: red, blue, yellow, black, and white; and these cannot be mixed indiscriminately. You will notice, for clarity, the flags shown are either red and white, yellow and blue, blue and white, or black and white; besides plain red, white, and blue.
One-flag signals are urgent or very common signals. Two-flag signals are mostly distress and maneuvering signals. Three-flag signals are for points of the compass, relative bearings, standard times, verbs, punctuation, also general code and decode signals. Four-flags are used for geographical signals, names of ships, bearings, etc. Five-flag signals are those relating to time and position. Six-flag signals are used when necessary to indicate north or south or east or west in latitude and longitude signals. Seven-flags are for longitude signals containing more than one hundred degrees.
The single signals were well recognized by professional seamen, but they used a code book for decoding groups of two, three, and four flags. For example, the two-letter group KT meant ‘you should send me a tow’ but if the numeral 1 was added it meant ‘I am sending a tow’. The letter group CB meant ‘I require immediate assistance’ but when it followed with a numeral 4 it meant ‘I require immediate assistance; I am aground’.
In today’s world of instant satellite communications, signalling by flag is almost a thing of the past, though some of the single flags, such as the blue peter, are still used. However, unlike semaphore, the International code of signals has not yet been made redundant by the International Maritime Organization which oversees international maritime communications.