ACP-131

ACP-131 is the controlling publication for the listing of Q codes and Z codes. It is published by the Combined Communications Electronics Board (CCEB) countries (Australia, New Zealand, Canada, United Kingdom and United States), and revised from time to time. When the meanings of the codes contained in ACP-131 are translated into various languages, the codes provide a means of communicating between ships of various nations, such as during a NATO exercise, when a common language is not in effect.

The original edition of ACP-131 was published by the U.S. military during the early years of radio telegraphy for use by radio operators using Morse Code on continuous wave (CW) telegraphy. It became especially useful, and even essential, to wireless radio operators on both military and civilian ships at sea before the development of advanced single-sideband telephony in the 1960s.

Radio communications, prior to the advent of landlines and satellites as communication paths and relays, was always subject to unpredictable fade outs caused by weather conditions, amount of emission power in kilowatts at the transmitter, radio frequency of the transmission, type of emission, type of transmitting antenna, signal basewave shape and size, sensitivity of the receiver and presence, or lack of presence, of atmospheric reflective layers above the earth, such as the E-layer and F-layers, the type of receiving antenna, the time of day, and numerous other factors.

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