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The Joint Army/Navy Phonetic Alphabet was a radio alphabet developed in 1941 and was used by all branches of the United States military until the promulgation of the ICAO spelling alphabet (Alfa, Bravo) in 1956, which replaced it. Before the Joint Army/Navy (JAN) phonetic alphabet, each branch of the armed forces used its own radio alphabet, leading to difficulties in interbranch communication.
Vestiges of the system remain in use in the U.S. Navy, in the form of Material Conditions of Readiness, used in damage control. Dog, William, X-Ray, Yoke, and Zebra all reference designations of fittings, hatches, or doors. The response "Roger" for "· – ·" or "R", to mean "received", also derives from this alphabet.
The names Able to Fox were also widely used in the early days of hexadecimal digital encoding of text in speaking of the hexadecimal digits equivalent to decimal 10 to 15, although the written form was simply the capital letters A to F. See hexadecimal.