The International Code of Signals (ICS) is an international system of signals and codes for use in boats, which aims to provide media in situations related essentially to safety of navigation and persons, especially when there are language difficulties. This code establishes a standardized alphabet (letters A to Z, and the ten digits), along with a spoken form of each letter (to avoid confusing similar sounding letters like ‘b’, ‘p’ and ‘v’ ), and the association of the alphabet with standardized indicators.
The International Code of Signals was drafted in 1855 by the British Board of Trade and published in 1857 in two parts: the first containing universal and international signals, and the second British signals only. Eighteen signal flags were used to make over 70,000 possible messages. After World War the International Radiotelegraph Conference (1927 Washington) considered a new code review. You will be prepared in seven languages: English, French, Italian, German, Spanish and Norwegian. The new version was completed in 1930 and was adopted by the International Conference held in Madrid in 1932, which also appointed a standing committee to review and control.
More info on spoken forms and meanings of each banner.