The use of flags, known as flaghoist communication, is a fast and accurate way to send information in daylight. Ships use flags as signals to send out messages to each other. The SOS distress signal (.-.) is probably the best known message in Morse code. Because Morse code has a long range, it was also used to transmit the international maritime emergency frequency (500 kHz), which was monitored by NATO ships at sea until the late 1990s. It was widely used in the 1890s for early radio communication, before it was possible to transmit voice.

Morse code transmits text through on-off tones, light-flashes or clicks. It assigns a word to each letter so that a letter's name begins with the letter itself. The NATO alphabet became effective in 1956 and, a few years later, turned into the established universal phonetic alphabet for all military, civilian and amateur radio communications. The NATO phonetic alphabet is useful to prevent spelling mistakes or miscommunication, especially when people from different countries with different accents and pronunciations work together. William Turner's painting of HMS Victory at Trafalgar, with the signal flags highlighted. The symbol is a combination of the letters 'N' and 'D' (for nuclear disarmament). Another standard – semaphore – inspired the peace sign. 'Bravo Zulu', typically signalled with naval flags on ships at sea and meaning 'well done' is also commonly used in written communication by the military, for example by replying 'BZ' to an email. Some standards can be found in everyday civilian and military life.

Not completely though: in certain situations NATO still encodes messages via Morse using light-flashes and other visual signals because they are difficult to detect electronically. However, while the phonetic alphabet is widely used and ships still use flag signals to communicate, other standards such as Morse code have become practically obsolete. If you have ever said 'Bravo' to mean 'B' when speaking on the phone for instance, then you have used one of the most recognised standards, the NATO phonetic alphabet. Click on the image to see a larger version. NATO phonetic alphabet, flags and signals.

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