Voice Procedure - Example Usage

Example Usage

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. Standardized 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:

Aircraft: Boston Tower, Warrior tree (three) fife foxtrot, holding short of two two right.
Tower: Warrior Tree fife foxtrot, Boston Tower, runway two two right, cleared for immediate takeoff.
Aircraft: Roger, tree fife foxtrot, cleared for immediate takeoff, two two right.

On telecommunications circuits, disambiguation is a critical function of voice procedure. Due to any number of variables, including radio static, a busy or loud environment, or similarity in the phonetics of different words, a critical piece of information can be misheard or misunderstood; for instance, a pilot being ordered to eleven thousand as opposed to seven thousand. To reduce ambiguity, critical information may be broken down and read as separate letters and numbers. To avoid error or misunderstanding, pilots will often read back altitudes in the tens of thousands using both separate numbers and the single word (example: given a climb to 10,000 ft, the pilot replies " climbing to One zero, Ten Thousand"). However, this is usually only used to differentiate between 10,000 and 11,000 ft since these are the most common altitude deviations. The runway number read visually as eighteen, when read over a voice circuit as part of an instruction, becomes one eight. In some cases a spelling alphabet is used (also called a radio alphabet or a phonetic alphabet) . Instead of the letters AB, the words Alpha Bravo are used. Main Street becomes Mike Alpha India November street, clearly separating it from Drain Street and Wayne Street. The numbers 5 and 9 are pronounced "fife" and "niner" respectively, since "five" and "nine" can sound the same over the radio.

Over fire service radios, phraseology may include words that indicate the priority of a message, for example:

Forty Four Truck to the Bronx, Urgent!

or

San Diego, Engine Forty, Emergency traffic!

Words may be repeated to modify them from traditional use in order to describe a critical message:

Evacuate! Evacuate! Evacuate!

Police Radios also use this technique to escalate a call that is quickly becoming an emergency.

Code 3! Code 3! Code 3!

Railroads have similar processes. When instructions are read to a locomotive engineer, they are preceded by the engineer's name, direction of travel, and the train or locomotive number. This reduces the possibility that a set of instructions will be acted on by the wrong locomotive engineer:

Five Sixty Six West, Engineer Jones, okay to proceed two blocks west to Ravendale.

Phraseology on telecommunications circuits may employ special phrases like ten codes, Sigalert, Quick Alert! or road service towing abbreviations such as T6. This jargon may abbreviate critical data and alert listeners by identifying the priority of a message. It may also reduce errors caused by ambiguities involving rhyming, or similar-sounding, words.