Voice procedure

Voice procedure includes various techniques used to clarify, simplify and standardise spoken communications over two-way radios, in use by the armed forces, in civil aviation, police and fire dispatching systems, citizens' band radio (CB), etc. Specially, for civil aviation, it used to be called aeronautical phraseology, and is also used for some railroad radio communications, such as on CSX Transportation.

Voice procedure communications are intended to maximize clarity of spoken communication and reduce misunderstanding. It consists of signalling protocol such as the use of abbreviated codes like the CB radio ten-code, Q codes in amateur radio and aviation, police codes, etc. and jargon.

Some elements of voice procedure are understood across many applications, but significant variations exist. The armed forces of the NATO countries have similar procedures in order to make cooperation easier and pseudo-military organisations often base their procedures on them, so some commonality exists there.

Some words with specialised meanings are used in radio communication throughout the English-speaking world, and in international radio communication, where English is the lingua franca. Note that the following list commingles incompatible terms used in different communication modes, each of which has its own terminology (e.g., no air-to-ground controller would ever use the term "10-4", a CB radio term).

Each area of usage will have its own subset of prowords, usually derived from the NATO set, but sometimes from earlier Q-code and morse operator practices.

Furthermore, the use of some special prowords is tightly controlled, with that word never used on the air in other contexts within that area of usage. Examples include "repeat" (for additional artillery fire in military communications), "take off" (granting permission for aircraft take off in airfield tower communications), "rescue" (rescue in progress in surf life saving), and "mayday" (safety-of-life emergency in maritime and aeronautics).

The Federal Aviation Administration uses the term phraseology to describe voice procedure or communications protocols used over telecommunications circuits. An example is air traffic control radio communications. Standardised wording is used and the person receiving the message may repeat critical parts of the message back to the sender. This is especially true of safety-critical messages. Consider this example of an exchange between a controller and an aircraft:

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