A spelling alphabet, voice procedure alphabet, radio alphabet, or telephone alphabet is a set of words used to stand for the letters of an alphabet in oral communication.
Each word in the spelling alphabet typically replaces the name of the letter with which it starts (acrophony). It is used to spell out words when speaking to someone not able to see the speaker, or when the audio channel is not clear. The lack of high frequencies on standard telephones makes it hard to distinguish an 'F' from an 'S' for example. Also, the lack of visual cues during oral communication can cause confusion. For example, lips are closed at the start of saying the letter "bee" but open at the beginning of the letter "dee" making these otherwise similar sounding letters more easily discriminated when looking at the speaker. Without these visual cues, such as during announcements of airline gate numbers "B1" and "D1" at an airport, "B" may be confused with "D" by the listener. Spelling out one's name, a password or a ticker symbol over the telephone are other scenarios where a spelling alphabet is useful.
A spelling alphabet is also often called a phonetic alphabet, especially by amateur radio enthusiasts, recreational sailors in the US and Australia, and NATO military organizations. However, this conflicts with the usage of the same phrase in phonetics to mean a notation used for phonetic transcription or phonetic spelling, such as the International Phonetic Alphabet, which is used to indicate the sounds of human speech.
Spelling alphabets are especially useful when speaking in a noisy environment when clarity and promptness of communication is essential, for example during two-way radio communication between an aircraft pilot and air traffic control, or in military operations. Whereas the names of many letters sound alike, the set of replacement words can be selected to be as distinct from each other as possible, to minimise the likelihood of ambiguity or mistaking one letter for another. For example, if a burst of static cuts off the start of an English-language utterance of the letter J, it may be mistaken for A or K. In the international radiotelephony spelling alphabet known as the ICAO (or NATO) phonetic alphabet, the sequence J-A-K would be pronounced Juliet-Alpha-Kilo. Some voice procedure standards require numbers to be spelled out digit by digit, so some spelling alphabets replace confusable digit names with more distinct alternatives; for example, the NATO alphabet has "niner" for 9 to distinguish it better from 5 and the German word "nein".
Prior to spelling alphabets, the words used to indicate English letters were "a", "bee", "cee", "dee", "e", etc. Their sounds are difficult to discriminate orally, hence the invention of telephone alphabets, and eventually radio alphabets, as used by armed services. Confusion of the oral indication of letters is not dangerous in most common situations, but in military applications it can have lethal consequences. Prior to radio and telephone, telegraph required no telephone alphabet because morse code served the same purpose and did not rely on human utterance of letters.
British Army signallers began using a partial spelling alphabet in the late 19th century. Recorded in the 1898 "Signalling Instruction" issued by the War Office and followed by the 1904 Signalling Regulations this system differentiated only the letters most frequently misunderstood: Ack (originally "Ak") Beer (or Bar) C D E F G H I J K L eMma N O Pip Q R eSses Toc U Vic W X Y Z. This alphabet was the origin of phrases such as "ack-ack" (A.A. for anti-aircraft), "pip-emma" for pm and Toc H for an ex-servicemen association. It was developed on the Western Front of the First World War. The RAF developed their "Telephony Spelling Alphabet" which was adopted by all three services, and civil aviation in the UK from 1921.
It was later formally codified to provide a phonetic equivalent for all 26 letters (see comparative tabulation of military alphabets before 1956).
For the general populace, and finance professionals in particular, phonetic alternatives such as "November" for the letter N and "Kilo" for the letter K were considered too long or obscure, and an alternative alphabet arose. Common first names were a popular choice, and as a result the First Name Alphabet (possibly first compiled by a US financial firm) has become quite commonly used.
For human languages:
- Latin script: For the Latin alphabets various Latin spelling alphabets exist. Most notably the ICAO spelling alphabet used in the international aviation industry.
- Greek script: The Greek spelling alphabet is a spelling alphabet for the Greek language, i.e. a set of names used in lieu of alphabet letters for the purpose of spelling out words. It is used by the Greek armed and emergency services.
- Cyrillic script: The Russian spelling alphabet is a spelling alphabet for the Russian Cyrillic alphabet.
The PGP word list, the Bubble Babble wordlist used by ssh-keygen, and the S/KEY dictionary, are spelling alphabets for public key fingerprints (or other binary data) -- i.e., a set of names given to data bytes for the purpose of spelling out binary data in a clear and unambiguous way via a voice channel.
- Marine radios (Maritime Safety Queensland)
- Phonetic Alphabet (ArmyStudyGuide.com) page 1
- "toc, n.". OED Online. September 2013. Oxford University Press. http://www.oed.com/view/Entry/202780?redirectedFrom=toc (accessed September 14, 2013)[dead link].
- Phonetic/spelling Alphabets for various languages from Brian Kelk's website
- Website converting text to telephone alphabet, (non-standard English, NATO, 14 other languages).
- Website converting text to NATO and several military English-language telephone alphabets
- Learn the NATO Radio Alphabet (and others) with flash cards game.