The NATO phonetic alphabet, more formally the international radiotelephony spelling alphabet, is the most widely used spelling alphabet. Though often called "phonetic alphabets", spelling alphabets have no connection to phonetic transcription systems like the International Phonetic Alphabet. Instead, the NATO alphabet assigns code words to the letters of the English alphabet acrophonically so that critical combinations of letters (and numbers) can be pronounced and understood by those who transmit and receive voice messages by radio or telephone regardless of their native language, especially when the safety of navigation or persons is essential. The paramount reason is to ensure intelligibility of voice signals over radio links. It is used by many national and international organizations, including the International Civil Aviation Organization (ICAO), the International Telecommunication Union (ITU), the International Maritime Organization (IMO), the North Atlantic Treaty Organisation (NATO), the Federal Aviation Administration (FAA), and the American National Standards Institute (ANSI). It is a subset of the much older International Code of Signals (INTERCO), which originally included visual signals by flags or flashing light, sound signals by whistle, siren, foghorn, or bell, as well as one, two, or three letter codes for many phrases.[1] The same alphabetic code words are used by all agencies, but each agency chooses one of two different sets of numeric code words. NATO uses the normal English numeric words (Zero, One, with some alternative pronunciations), whereas the IMO uses compound numeric words (Nadazero, Unaone). The alphabet's common name (NATO phonetic alphabet) arose because it appears in Allied Tactical Publication ATP-1, Volume II: Allied Maritime Signal and Maneuvering Book used by all allied navies in NATO, which adopted a modified form of the International Code of Signals. Because the latter allows messages to be spelled via flags or Morse code, it naturally called the code words used to spell out messages by voice its "phonetic alphabet". The name NATO phonetic alphabet became widespread because the signals used to facilitate the naval communications and tactics of the United States and NATO have become global.[2] However, ATP-1 is marked NATO Confidential (or the lower NATO Restricted) so it is not publicly available. Nevertheless, a NATO unclassified version of the document is provided to foreign, even hostile, militaries, even though they are not allowed to make it publicly available. Phonetic Alphabet (as incorporated by IMO) Alfa Bravo Charlie Delta Echo Foxtrot Golf Hotel India Juliett Kilo Lima Mike November Oscar Papa Quebec Romeo Sierra Tango Uniform Victor Whiskey Xray Yankee Zulu 0 Nadazero 1 Unaone 2 Bissotwo 3 Terrathree 4 Kartefour 5 Pantafive 6 Soxisix 7 Setteseven 8 Oktoeight 9 Novenine