NATO phonetic alphabet
The International Radiotelephony Spelling Alphabet, commonly known as the NATO phonetic alphabet, NATO spelling alphabet, ICAO phonetic alphabet or ICAO spelling alphabet, is the most widely used radiotelephone spelling alphabet. The ITU phonetic alphabet and figure code is a rarely used variant that differs in the code words for digits. To create the code, a series of international agencies assigned 26 code words acrophonically to the letters of the English alphabet, so that the names for letters and numbers would be as distinct as possible so as to be easily understood by those who exchanged voice messages  by radio or telephone, regardless of language differences or the quality of the connection. The specific code words varied, as some seemingly distinct words were found to be ineffective in real-life conditions. In 1956, NATO modified the then-current set of code words used by the International Civil Aviation Organization (ICAO); this modification then became the international standard when it was accepted by the ICAO that year and by the International Telecommunication Union (ITU) a few years later. The words were chosen to be accessible to speakers of French and Spanish in addition to English; the spellings of a  couple of code words were changed to facilitate their use. Spelling alphabets are often inaccurately called "phonetic alphabets", but they do not indicate phonetics and cannot function as phonetic transcription systems like the International Phonetic Alphabet. The 26 code words are as follows: , Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, , Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu. Numbers are read off as English digits, but the pronunciations of "three, four, five, nine" and "thousand" are modified. Strict adherence to the prescribed spellingsincluding the apparently misspelled "Alfa" and "Juliett"is  required in order to avoid the problems of confusion that the code is designed to overcome. A 1955 NATO memo stated that: International adoption. After the phonetic alphabet was developed by the International Civil Aviation Organization (ICAO) (see history below) it was adopted by many other international and national organizations, including the International Telecommunication Union (ITU), the International Maritime Organization (IMO), the United States Federal Government as Federal Standard 1037C: Glossary of Telecommunications Terms, and its successors ANSI T1.523-2001 and ATIS Telecom Glossary (ATIS-0100523.2019), (using the English spellings "Alpha" and "Juliet"), the United States Department of Defense (using standard  spellings), the Federal Aviation Administration (FAA), and the International Amateur Radio Union (IARU), the American Radio Relay League (ARRL), the Association of Public-Safety Communications Officials-International (APCO); and by many military organizations such as the North Atlantic Treaty Organization (NATO) and the now-defunct Southeast Asia Treaty Organization (SEATO). 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 regular English numeric words (Zero, One, with some alternative pronunciations), whereas the ITU (beginning on 1 April 1969) and the IMO define compound numeric  words (Nadazero, Unaone, Bissotwo...). In practice these are used very rarely, as they frequently result in confusion between speakers of different languages. Usage. A spelling alphabet is used to spell parts of a message containing letters and numbers to avoid confusion, because many letters sound similar, for instance "n" and "m" or "f" and "s"; the potential for confusion increases if static or other interference is present. For instance the message "proceed to map grid DH98" could be transmitted as "proceed to map grid Delta-Hotel-Niner-Ait". Using "Delta" instead of "D" avoids confusion between "DH98" and "BH98" or  TH98. The unusual pronunciation of certain numbers was designed to reduce confusion as well. In addition to the traditional military usage, civilian industry uses the alphabet to avoid similar problems in the transmission of messages by telephone systems. For example, it is often used in the retail industry where customer or site details are spoken by telephone (to authorize a credit agreement or confirm stock codes), although ad-hoc coding is often used in that instance. It has been used often by information technology workers to communicate serial or reference codes (which are often very long) or other specialised information  by voice. Most major airlines use the alphabet to communicate passenger name records (PNRs) internally, and in some cases, with customers. It is often used in a medical context as well, to avoid confusion when transmitting information. Several letter codes and abbreviations using the spelling alphabet have become well-known, such as Bravo Zulu (letter code BZ) for "well done", Checkpoint Charlie (Checkpoint C) in Berlin, and Zulu Time for Greenwich Mean Time or Coordinated Universal Time. During the Vietnam War, the U.S. government referred to the Viet Cong guerrillas and the group itself as VC, or Victor Charlie; the  name "Charlie" became synonymous with this force. Pronunciation of code words. The final choice of code words for the letters of the alphabet and for the digits was made after hundreds of thousands of comprehension tests involving 31 nationalities. The qualifying feature was the likelihood of a code word being understood in the context of others. For example, "football" has a higher chance of being understood than "foxtrot" in isolation, but "foxtrot" is superior in extended communication. The pronunciation of the code words varies according to the language habits of the speaker. To eliminate wide variations in pronunciation, recordings and  posters illustrating the pronunciation desired by the ICAO are available. However, there are still differences in pronunciation between the ICAO and other agencies, and the ICAO has conflicting Latin-alphabet and International Phonetic Alphabet (IPA) transcriptions. Also, although all codes for the letters of the alphabet are English words, they are not in general given English pronunciations. Pronunciations are somewhat uncertain because the agencies, while ostensibly using the same pronunciations, give different transcriptions, which are often inconsistent from letter to letter. The ICAO gives a different pronunciation for IPA transcription and for respelling. The Alliance for Telecommunications Industry Solutions (ATIS ) gives English spellings, but does not give pronunciations or numbers. The ICAO, NATO, and FAA use modifications of English numerals, with stress on one syllable, while the ITU and IMO compound pseudo-Latinate numerals with a slightly different set of modified English numerals, and with stress on each syllable. Numbers 10–99 are spelled out (that is, 17 is spoken "one seven" and 60 is spoken "six zero"), while for hundreds and thousands the English words "hundred" and "thousand" are used.<ref name="FAA-FAR/AIM"></ref> The pronunciation of the digits 3, 4, 5, and 9 differs from standard English – being pronounced  tree, "fower", "fife", and "niner". The digit 3 is specified as "tree" so that it is not pronounced "sri"; the long pronunciation of 4 (still found in some English dialects) keeps it somewhat distinct from "for"; 5 is pronounced with a second "f" because the normal pronunciation with a "v" is easily confused with "fire" (a command to shoot); and 9 has an extra syllable to keep it distinct from German "nein" 'no'. Only the ICAO prescribes pronunciation with the IPA, and then only for letters. Several of the pronunciations indicated are slightly modified from their normal English pronunciations, partially  due to the substitution of final schwas with the vowel. Both the IPA and respelled pronunciations were developed by the ICAO before 1956 with advice from the governments of both the United States and United Kingdom. In addition, the ITU and IMO specify a different set of numeral words than does the ICAO. The ITU/IMO words are compounds combining the English numeral with either a Spanish or Latin prefix. However, as of 2002, the IMO's GMDSS procedures permit the use of the ICAO numeral pronunciation. History. Prior to World War I and the development and widespread adoption of  two-way radio that supported voice, telephone spelling alphabets were developed to improve communication on low-quality and long-distance telephone circuits. The first non-military internationally recognized spelling alphabet was adopted by the CCIR (predecessor of the ITU) during 1927. The experience gained with that alphabet resulted in several changes being made during 1932 by the ITU. The resulting alphabet was adopted by the International Commission for Air Navigation, the predecessor of the ICAO, and was used for civil aviation until World War II. It continued to be used by the IMO until 1965. Throughout World War II, many  nations used their own versions of a spelling alphabet. The U.S. adopted the Joint Army/Navy radiotelephony alphabet during 1941 to standardize systems among all branches of its armed forces. The U.S. alphabet became known as "Able Baker" after the words for A and B. The Royal Air Force adopted one similar to the United States one during World War II as well. Other British forces adopted the RAF radio alphabet, which is similar to the phonetic alphabet used by the Royal Navy during World War I. At least two of the terms are sometimes still used by UK civilians  to spell words over the phone, namely "F for Freddie" and "S for Sugar". To enable the U.S., UK, and Australian armed forces to communicate during joint operations, in 1943 the CCB (Combined Communications Board; the combination of US and UK upper military commands) modified the U.S. military's Joint Army/Navy alphabet for use by all three nations, with the result being called the US-UK spelling alphabet. It was defined in one or more of CCBP-1: "Combined Amphibious Communications Instructions", CCBP3: "Combined Radiotelephone (R/T) Procedure", and CCBP-7: "Combined Communication Instructions." The CCB alphabet itself was based on  the U.S. Joint Army/Navy spelling alphabet. The CCBP (Combined Communications Board Publications) documents contain material formerly published in U.S. Army Field Manuals in the 24-series. Several of these documents had revisions, and were renamed. For instance, CCBP3-2 was the second edition of CCBP3. During World War II, the U.S. military conducted significant research into spelling alphabets. Major F. D. Handy, directorate of Communications in the Army Air Force (and a member of the working committee of the Combined Communications Board), enlisted the help of Harvard University's Psycho-Acoustic Laboratory, asking them to determine the most successful  word for each letter when using "military interphones in the intense noise encountered in modern warfare.". He included lists from the US, Royal Air Force, Royal Navy, British Army, AT&T, Western Union, RCA Communications, and that of the International Telecommunications Convention. According to a report on the subject: After World War II, with many aircraft and ground personnel from the allied armed forces, "Able Baker" was officially adopted for use in international aviation. During the 1946 Second Session of the ICAO Communications Division, the organization adopted the so-called "Able Baker" alphabet that was the 1943 US–UK spelling alphabet . But many sounds were unique to English, so an alternative "Ana Brazil" alphabet was used in Latin America. But the International Air Transport Association (IATA), recognizing the need for a single universal alphabet, presented a draft alphabet to the ICAO during 1947 that had sounds common to English, French, Spanish and Portuguese. From 1948 to 1949, Jean-Paul Vinay, a professor of linguistics at the Université de Montréal worked closely with the ICAO to research and develop a new spelling alphabet. ICAO's directions to him were that "To be considered, a word must: After further study and modification by  each approving body, the revised alphabet was adopted on , to become effective on 1 April 1952 for civil aviation (but it may not have been adopted by any military). Problems were soon found with this list. Some users believed that they were so severe that they reverted to the old "Able Baker" alphabet. Confusion among words like "Delta" and "Extra", and between "Nectar" and "Victor", or the unintelligibility of other words during poor receiving conditions were the main problems. Later in 1952, ICAO decided to revisit the alphabet and their research. To identify the deficiencies of the new alphabet, testing  was conducted among speakers from 31 nations, principally by the governments of the United Kingdom and the United States. In the United States, the research was conducted by the USAF-directed Operational Applications Laboratory (AFCRC, ARDC), to monitor a project with the Research Foundation of Ohio State University. Among the more interesting of the research findings was that "higher noise levels do not create confusion, but do intensify those confusions already inherent between the words in question". By early 1956 the ICAO was nearly complete with this research, and published the new official phonetic alphabet in order to account for  discrepancies that might arise in communications as a result of multiple alphabet naming systems coexisting in different places and organizations. NATO was in the process of adopting the ICAO spelling alphabet, and apparently felt enough urgency that it adopted the proposed new alphabet with changes based on NATO's own research, to become effective on 1 January 1956, but quickly issued a new directive on 1 March 1956 adopting the now official ICAO spelling alphabet, which had changed by one word (November) from NATO's earlier request to ICAO to modify a few words based on U.S. Air Force research . After all of the above study, only the five words representing the letters C, M, N, U, and X were replaced. The ICAO sent a recording of the new "Radiotelephony Spelling Alphabet" to all member states in November 1955. The final version given in the table above was implemented by the ICAO on , and the ITU adopted it no later than 1959 when they mandated its usage via their official publication, "Radio Regulations". Because the ITU governs all international radio communications, it was also adopted by most radio operators, whether military, civilian, or amateur. It was finally adopted by the  IMO in 1965. During 1947 the ITU adopted the compound Latinate prefix-number words ("Nadazero", "Unaone", etc.), later adopted by the IMO during 1965. In the official version of the alphabet, the non-English spellings Alfa and Juliett are used. "Alfa" is spelled with an "f" as it is in most European languages because the English and French spelling "alpha" would not be pronounced properly by native speakers of some other languages – who may not know that "ph" should be pronounced as "f". "Juliett" is spelled with a "tt" for French speakers, because they may otherwise treat a single final  t as silent. Some published versions use the English spellings "Alpha" and "Juliet"presumably because of the use of spell checker software. Defined by various international conventions on radio, including: Tables. For the 1938 and 1947 phonetics, each transmission of figures is preceded and followed by the words "as a number" spoken twice. The ITU adopted the International Maritime Organization's phonetic spelling alphabet in 1959, and in 1969 specified that it be "for application in the maritime mobile service only". Pronunciation was not defined prior to 1959. For the 1959 – present phonetics, the underlined syllable of each letter word should  be emphasized, and each syllable of the code words for the figures (1969 – present) should be equally emphasized. International aviation. The Radiotelephony Spelling Alphabet is used by the International Civil Aviation Organization for international aircraft communications. International maritime mobile service. The ITU-R Radiotelephony Alphabet is used by the International Maritime Organization for international marine communications.