Aeronautical mobile procedure 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:
Aircraft: Boston Tower, Warrior three five foxtrot (35F), holding short of two two right.
Tower: Warrior three five foxtrot, Boston Tower, runway two two right, cleared for immediate takeoff.
Aircraft: Roger, cleared for immediate takeoff, two two right, Warrier three five foxtrot. 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 (by hearing "even"). 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 "[Callsign] 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. The use of 'niner' in place of 'nine' is due to German-speaking NATO allies for whom the spoken word 'nine' could be confused with the German word 'nein' or 'no'. 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! A similar technique may be used in aviation for critical messages. For example, this transmission might be sent to an aircraft that has just landed and has not yet cleared the runway. Echo-Foxtrot-Charlie, Tower. I have engine out traffic on short final. Exit runway at next taxiway. Expedite! Expedite! 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 train or locomotive number, direction of travel and the engineer's name. 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.
Maritime mobile procedure (Done on VHF Ch 16) Boat "Albacore" talking to Boat "Bronwyn"
Albacore: Bronwyn, Bronwyn, Bronwyn* this is Albacore, OVER. (*3×1, repeating the receiver's callsign up to 3 times, and the sender's once, is proper procedure and should be used when first establishing contact, especially over a long distance. A 1×1, i.e. 'Bronwyn this is Albacore,' or 2×1, i.e. 'Bronwyn, Bronwyn, this is Albacore,' is less proper, but acceptable especially for a subsequent contact.)
Bronwyn: Albacore, this is Bronwyn, OVER. (** At this point switch to a working channel as 16 is for distress and hailing only**)
Albacore: This is Albacore. Want a tow and are you OK for tea at Osbourne Bay? OVER.
Bronwyn: This is Bronwyn. Negative, got engine running, 1600 at clubhouse fine with us. OVER.
Albacore: This is Albacore, ROGER, OUT. "Copy that" is incorrect. COPY is used when a message has been intercepted by another station, i.e. a third station would respond:
Nonesuch: Bronwyn, this is Nonesuch. Copied your previous, will also see you there, OUT. One should always use one's own callsign when transmitting.
British Army Station C21A (charlie-two-one Alpha) talking to C33B (charlie-three-three Bravo):
C21A: C33B, this is C21A, message, OVER.
C33B: C33B, send, OVER.
C21A: Have you got C1ØD Sunray at your location?, OVER.
C33B: Negative, I think he is with C3ØC, OVER.
C21A: Roger, OUT. The advantage of this sequence is that the recipient always knows who sent the message. The downside is that the listener only knows the intended recipient from the context of the conversation. Requires moderate signal quality for the radio operator to keep track of the conversations. However a broadcast message and response is fairly efficient.
Sunray (Lead) Charlie Charlie (Collective Call - everyone), this is Sunray. Radio check, OVER.
C-E-5-9: Sunray, this is Charlie Echo five niner, LOUD AND CLEAR, OVER.
Y-S-7-2 Sunray, this is Yankee Sierra Seven Two, reading three by four. OVER.
B-G-5-2: Sunray, this is Bravo Golf Five Two, Say again. OVER.
E-F-2-0: Sunray, this is Echo Foxtrot Two Zero, reading Five by Four OVER.
Sunray: Charlie Charlie this is Sunray, OUT. The "Say again" response from B-G-5-2 tells Sunray that the radio signal is not good and possibly unreadable. Sunray can then re-initiate a Call onto B-G-5-2 and start another R/C or instruct them to relocate, change settings, etc. So it could carry on with:
Sunray: Bravo Golf Five Two this is sunray, RADIO CHECK OVER.
B-G-5-2: Sunray this is Bravo Golf Five Two, unclear, read you 2 by 3 OVER.
Sunray: Sunray copies, Relocate to Grid One Niner Zero Three Three Two for a better signal OVER.
B-G-5-2: Bravo Golf Five Two copies and is Oscar Mike, Bravo Golf Five Two OUT. == See also ==