ACP-131 is the controlling publication for the listing of and It is published and revised from time to time by the Combined Communications Electronics Board (CCEB) countries: Australia, New Zealand, Canada, United Kingdom, and United States. 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 The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...

exercise, where there is no common

language Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed language, signed forms, and may also be conveyed through writing syste ...

History

The original edition of ACP-131 was published by the U.S. military during the early years of

radio Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...

telegraphy Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas pi ...

for use by radio operators using

Morse Code Morse code is a telecommunications method which Character encoding, encodes Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code i ...

continuous wave A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration. It may refer to e.g. a laser or particl ...

(CW) telegraphy. It became especially useful, and even essential, to

wireless Wireless communication (or just wireless, when the context allows) is the transfer of information (''telecommunication'') between two or more points without the use of an electrical conductor, optical fiber or other continuous guided transm ...

radio operators on both military and civilian ships at sea before the development of advanced single-sideband

telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is ...

in the 1960s.

Reason for the codes

Radio communications, prior to the advent of landlines and

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

s as communication paths and relays, was always subject to unpredictable fade outs caused by

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmo ...

conditions, practical limits on available emission power at the

transmitter In electronics and telecommunications, a radio transmitter or just transmitter (often abbreviated as XMTR or TX in technical documents) is an electronic device which produces radio waves with an antenna (radio), antenna with the purpose of sig ...

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the u ...

of the transmission, type of emission, type of transmitting antenna,

signal A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology. In ...

waveform characteristics, modulation scheme in use, 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. Because of these factors which often resulted in limiting periods of transmission time on certain frequencies to only several hours a day, or only several minutes, it was found necessary to keep each wireless transmission as short as possible and to still get the message through. This was particularly true of CW radio circuits shared by a number of operators, with some waiting their turn to transmit. As a result, an operator communicating by

radio telegraphy Wireless telegraphy or radiotelegraphy is the transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term ''wireless telegraphy'' was also used for other experimental technologies fo ...

to another operator, wanting to know how the other operator was receiving the signal, could send out a message on his key in

stating, "How are you receiving me?" : Using ACP-131 codes, the question could be phrased simply "" : resulting in much more efficient use of circuit time. If the receiver hears the sender in a "loud and clear" condition, the response would be "": : All of which requires less circuit time and less "pounding" on the key by the sending operators. Should the receiving operator not understand the sending operator, the receiving operator would send "" : or the marginally shorter : The other operator would respond again with: : which is much easier than retransmitting "How are you receiving me?" If the receiving operator understood the sending operator, the receiving operator would say the word "ROGER" or "MESSAGE RECEIVED", or the send the short form "" : "" and "" are similarly structured, but very easy to distinguish.

Applicability of the codes

According to ACP-125(F), paragraphs 103 and 104, in radio communication among Allied military units: * Q codes are authorized for both civilian and military use, and for communications between the two. * Z codes are authorized for use only among military stations. :

Voice transmission

Some assert that the use of Q codes and Z codes was not intended for use on voice circuits, where plain language was speedy and easily recognizable, especially when employing the character recognition system in use at the time, such as ''ALPHA'', ''BRAVO'', ''CHARLIE'', ''etc''. However, in military communication the latter are still in use.Unclassified NATO naval-communication practices / manuals in Northern Europe A typical simplex military voice exchange: : However, some voice operators, such as

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...

operators, find it convenient or traditional to carry over some of the Q codes to voice ("phone") exchanges, such as "QSL", "QRK", "QTH", ''etc''.

Footnotes

References

External links

* * {{Telecommunications Brevity codes Military standardization Military publications Military radio systems Amateur radio Encodings Maritime communication History of radio