User:PetesGuide/Procedure sign

Procedure signs or prosigns are shorthand signals used in radio telegraphy procedures, for the purpose of simplifying and standardizing communications related to radio operating issues among two or more radio operators. They are distinct from general Morse code abbreviations, which consist mainly of brevity codes that convey messages to other parties with greater speed and accuracy.

The development of prosigns began development in the 1860s for wired telegraphy. They can be distinguished from abbreviations because prosigns have exact equivalents for radio telephony (voice) procedure words.

Although as written, some of the prosigns appear to be simply two adjacent letters, most prosigns are instead digraphs that have zero spacing between the patterns that represent the "combined" letters, and are properly written with an overbar (if more than one single character) to indicate this. The difference is subtle, but the meaning is not. For example, the prosign $\overline{AA}$ has the same meaning as the voice procedure word UNKNOWN STATION, but the prosign AA  has the same meaning as the voice procedure word "ALL AFTER", and is used to indicate that part of the previously transmitted message needs to be re-transmitted; the only difference between the Morse code prosigns is an inter-letter space between the two "dot dash dot dash" sequences".

Official International Morse code procedure signs
The procedure signs below are compiled from the official specification for Morse Code, ITU-R M.1677, International Morse Code, while others are defined the International Radio Regulations, including ITU-R M.1170, ITU-R M.1172 , ITU-R M.1677-1 , and the International Code of Signals, with a few details of their usage appearing in ACP-131, which otherwise defines operating signals, not procedure signals. text

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