Radiotelephony procedure

In the U.S., radio communications are regulated by the NTIA and the FCC. Regulations created by the FCC are codified in Title 47 of the Code of Federal Regulations:

• Part 4—Disruptions to Communications
• Part 20—Commercial Mobile Services
• Part 80—Stations in the Maritime Services (Maritime Mobile Service)
• Part 87—Aviation Services
• Part 90—Private Land Mobile Radio Services (Concerning licensed wireless communications for businesses and non-federal governments)
  • Subpart C—Business Band
• Part 95—Personal Radio Services (MURS, FRS, GMRS, and CB radio)
• Part 97—Amateur Radio Service (Ham radio)
• Part 300—NTIA Rules and Regulations

Each country is assigned a range of prefixes, and the radiotelecommunications agencies within each country then responsible for allocating call signs, within the format defined by the RR, as they see fit. The Radio Regulations require most radio stations to regularly identify themselves by means of their official station call sign or other unique identifier.

Because official radio call signs have no inherent meaning outside of the above-described patterns, and other than individually licensed Amateur radio stations, do not serve to identify the person using the radio, they are not usually desirable as the primary means of identifying which person, department, or function is transmitting or is being contacted.

For this reason, functional designators (a.k.a. tactical call signs) are frequently used to provide such identification. Such designators are not sufficient to meet the FCC requirements that stations regularly identify the license they are operating under, typically every x number of minutes and at the end of each transmission, where x ranges from 10 to 30 minutes (longer for broadcast stations).

For the some radio services, the FCC authorizes alternate station IDs,[6] typically in situations where the alternate station ID serves the purposes of identifying the transmitting station better than the standard ITU format. These include:

• Aircraft—the registration number (tail number) of the aircraft, preceded by the type (typical of general aviation aircraft); or the aircraft operator nickname assigned by the FAA, followed by the flight number (typical of scheduled airline services).
• Land mobile—Name of the station licensee (typically abbreviated), location of station, name of city, or facility served, followed by additional digits following the more general ID.
• Land mobile railroad—Name of railroad, followed by the train number, engine number etc.

The United States has been assigned all call signs with the prefixes K, N, and W, as well as AAA–ALZ. Allocating call signs within these groups is the responsibility of the National Telecommunications and Information Administration (almost all government stations) or the Federal Communications Commission (all other stations), and they subdivide the radio call signs into the following groups:

• AAA–AEZ and ALA–ALZ are reserved for Department of the Army stations
• AFA–AKZ are assigned to the Department of the Air Force
• NAA–NZZ is jointly assigned to the Department of the Navy and the U.S. Coast Guard.

Ham station call signs begin with A, K, N or W, and have a single digit from 0 to 9 that separates the 1 or 2 letter prefix from the 1 to 3 letter suffix (special event stations have only three characters: the prefix, the digit, and a one-letter suffix).[7]

Maritime call signs have a much more complex structure, and are sometimes replaced with the name of the vessel or a Maritime Mobile Service Identity (MMSI) number.

Several radio operation procedures manuals, including ACP 125(G) teach the same mnemonic of Rhythm, Speed, Volume, and Pitch (RSVP):[13]

Rhythm

Use short sentences divided into sensible phrases which maintain a natural rhythm; they should not be spoken word by word. Where pauses occur, the press-to-talk should be released to minimize transmission time and permit stations to break in when necessary.

Speed

Speak slightly slower than for normal conversation. Where a message is to be written down by the recipients, or in difficult conditions, extra time should be allowed to compensate for the receiving station experiencing the worst conditions. Speed of transmission is easily adjusted by increasing or decreasing the length of pauses between phrases, as opposed to altering the gaps between words; the latter will create an unnatural, halted style of speech, which is difficult to understand.

Volume

Speak quietly when using whisper facilities, otherwise the volume should be as for normal conversation. Shouting causes distortion.

Pitch

The voice should be pitched slightly higher than for normal conversation to improve clarity.[14]

According to the UK's Radiotelephony Manual, CAP 413, radio operators should talk at a speed of fewer than 100 words per minute.

The initialism ABC is commonly used as a memory aid to reinforce the three most important rules about what to transmit.[19]

Whenever a report or a request is transmitted over a two-way radio, the operator should consider including the standard Five Ws in the transmission, so as to eliminate additional requests for information that may occur and thereby delay the request (and other communications).

1. Who—needs something
2. What—do they need
3. Why—do they need it
4. When—do they need it
5. Where—do they need it

• Think before you speak[20]
• Listen before you speak[20]
• Answer all calls promptly[20]
• Keep the airways free of unnecessary talk[20]
• Be brief and to the point[20]
• Only transmit facts[21]
• Do not act as a relay station unless the net control asks for one[21]

However, the international aviation and maritime industries, because their global expansion in the 20th century coincided with, and were heavily integral to the development of voice procedures and other aspects in the development of two-way radio technology, gradually developed their own variations on these procedures.

Voice communications procedures for international air traffic control and communications among airplanes are defined by the following International Civil Aviation Organization documents:

• Annex 10—Aeronautical Telecommunications, Volume II—Communications Procedures including those with PANS status,[22][23]
• Procedures for Air Navigation Services—Air Traffic Management (PANS-ATM, ICAO Doc 4444)[24]
• ICAO Doc 9432 (AN/925) Manual of Radiotelephony.[25]

Refinements and localization of these procedures can be done by each member country of ICAO.

• United States
  • FAA Pilot Controller Glossary[26]
• United Kingdom
  • Civil Aviation Authority's Radiotelephony manual[27]

Voice procedures for use on ships and boats are defined by the International Telecommunication Union and the International Maritime Organization bodies of the United Nations, and by international treaties such as the Safety of Life a Sea Convention (a.k.a. SOLAS 74), and by other documents, such as the International Code of Signals.

• ITU Radio Regulations
  • Appendix 18
• ITU maritime recommendations
  • ITU-R M.1171: Radiotelephony procedures in the maritime mobile service.[28]
• IMO resolutions
  • Resolution A.918(22) (covers Standard Marine Communication Phrases)

In the U.S., the organization chartered with devising police communications procedures is APCO International, the Association of Police Communications Officers, which was founded in 1935. For the most part, APCO's procedures have been developed independently of the worldwide standard operating procedures, leading to most police departments using a different spelling alphabet, and the reverse order of calling procedure (e.g. 1-Adam-12 calling Dispatch).

However, APCO occasionally follows the international procedure standards, having adopted the U.S. Navy's Morse code procedure signs in the 1930s, and adopting the ICAO radiotelephony spelling alphabet in 1974, replacing its own Adam-Boy-Charles alphabet adopted in 1940, although very few U.S. police departments made the change.

APCO has also specified Standard Description Forms, a standard order of reporting information describing people and vehicles.

The Standard Description of Persons format first appeared in the April 1950 edition of the APCO Bulletin.[29] It starts with a description of the person themself and finishes with a description of what they are wearing at the time.

APCO promotes the mnemonic CYMBALS for reporting vehicle descriptions:[29]

The voice calling procedure (sometimes referred to as "method of calling" or "communications order model") is the standardized method of establishing communications. The order of transmitting the called station's call sign, followed by the calling station's call sign, was first specified for voice communications in the International Radiotelegraph Convention of Washington, 1927,[30] however it matches the order used for the radiotelegraph calling procedure that had already existed since at least 1912. In the United States, the radiotelegraph calling procedure is legally defined in FCC regulations Part 80.97 (47 CFR 80.97(c)), which specifies that the method of calling begins with the call sign of the station called, not more than twice, [THIS IS] and the call sign of the calling station, not more than twice".[31] This order is also specified by the ICAO for international aviation radio procedures (Annex 10 to the Convention on. International Civil Aviation: Aeronautical Telecommunications.[32]), the FAA (Aeronautical Information Manual[33]) and by the ITU-R for the Maritime Mobile Service (ITU-R M.1171),[34] and the U.S. Coast Guard (Radiotelephone Handbook[35]). The March, 1940 issue of The APCO Bulletin explains the origin of this order was found to have better results than other methods,[36]

1. MUST give the callsign of the station you are calling, twice (never three times)
2. MUST follow the callsign with the proword THIS IS
3. MUST give your callsign once, and once only
4. Communicate
5. SHOULD end your transmission with the proword OVER, or OUT, although this can be omitted when using a repeater that inserts a courtesy tone at the end of each transmission.

Stations needing to interrupt other communications in-progress shall use the most appropriate of the below procedure words, followed by their call sign.

The use of these emergency signals is governed by the International Radio Regulations that have the force of law in most countries, and were originally defined in the International Code of Signals and the International Convention for the Safety of Life at Sea, so the rules for their use emanate from that document.

All of these break-in procedure words must be followed by your call sign, because that information will help the NCS determine the relevant importance when dealing with multiple break-ins of the same precedence, and to determine the relevance when multiple calls offering a CORRECTION or INFO are received.

The priority levels described below are derived from Article 44 of the ITU Radio Regulations, Chapter VIII, and were codified as early as the International Telecommunication Convention, Atlantic City, 1947 (but probably existed much earlier).

Procedure words are a direct voice replacement for procedure signs (prosigns) and operating signals (such as Q codes), and must always be used on radiotelephone channels in their place. Prosigns/operating signals may only be used with Morse Code (as well as semaphore flags, light signals, etc.) and TTY (including all forms of landline and radio teletype, and Amateur radio digital interactive modes). The most complete set of procedure words is defined in the U.S. Military's Allied Communications Publication ACP 125(G).[9]

Whenever an operator is transmitting and uncertain of how good their radio and/or voice signal are, they can use the following procedure words to ask for a signal strength and readability report. This is the modern method of signal reporting that replaced the old 1 to 5 scale reports for the two aspects of a radio signal, and as with the procedure words, are defined in ACP 125(G):

The prowords listed below are for use when initiating and answering queries concerning signal strength and readability.

In the tables below, the mappings of the QSA and QRK Morse code prosigns is interpreted because there is not a 1:1 correlation. See QSA and QRK code for the full procedure specification.

The reporting format is one of the signal strength prowords followed by an appropriate conjunction, with that followed by one of the readability prowords:

LOUD AND CLEAR means Excellent copy with no noise

GOOD AND READABLE means Good copy with slight noise

FAIR BUT READABLE means Fair copy, occasional fills are needed

WEAK WITH INTERFERENCE means Weak copy, frequent fills are needed because of interference from other radio signals.

WEAK AND UNREADABLE means Unable to copy, a relay is required

According to military usage, if the response would be LOUD AND CLEAR, you may also respond simply with the proword ROGER. However, because this reporting format is not currently used widely outside of military organizations, it is better to always use the full format, so that there is no doubt about the response by parties unfamiliar with minimization and other shorthand radio operating procedures.

The International Civil Aviation Organization (ICAO), International Telecommunication Union, and the International Maritime Organization (all agencies of the United Nations), plus NATO, all specify the use of the ICAO Radiotelephony Spelling Alphabet for use when it is necessary to spell out words, callsigns, and other letter/number sequences. It was developed with international cooperation and ratified in 1956, and has been in use unmodified ever since.

Spelling is necessary when difficult radio conditions prevent the reception of an obscure word, or of a word or group, which is unpronounceable. Such words or groups within the text of plain language messages may be spelt using the phonetic alphabet; they are preceded by the proword "I SPELL". If the word is pronounceable and it is advantageous to do so, then it should be spoken before and after the spelling to help identify the word.[44]

When radio conditions are satisfactory and confusion will not arise, numbers in the text of a message may be spoken as in normal speech. During difficult conditions, or when extra care is necessary to avoid misunderstanding, numbers are sent figure by figure preceded by the proword FIGURES. This proword warns that figures follow immediately, to help distinguish them from other similarly pronounced words.[44]

Ending a two-way radio call has its own set of procedures:

• Generally, the station that originated the call is the station that should initiate termination of the call.
• All stations indicate their last transmission of a particular communication exchange by using the proword OUT (I intend no further communication with you at this time) or OUT TO YOU (I am ending my communication with you and calling another station).
• Stations going off the air (specifically turning their radio equipment off or leaving the station unattended) can additionally state that they are "closing" or "closing down", based on the proword command "CLOSE DOWN".

A net manager is the person who supervises the creation and operation of a net over multiple sessions. This person will specify the format, date, time, participants, and the net control script. The net manager will also choose the Net Control Station for each net, and may occasionally take on that function, especially in smaller organizations.

Radio nets are like conference calls in that both have a moderator who initiates the group communication, who ensures all participants follow the standard procedures, and who determines and directs when each other station may talk. The moderator in a radio net is called the Net Control Station, formally abbreviated NCS, and has the following duties:[46]

• Establishes the net and closes the net;
• Directs Net activities, such as passing traffic, to maintain optimum efficiency;
• Chooses net frequency, maintains circuit discipline and frequency accuracy;
• Maintains a net log and records participation in the net and movement of messages; (always knows who is on and off net)
• Appoints one or more Alternate Net Control Stations (ANCS);
• Determines whether and when to conduct network continuity checks;
• Determines when full procedure and full call signs may enhance communications;
• Subject to Net Manager guidance, directs a net to be directed or free.

The Net Control Station will, for each net, appoint at least one Alternate Net Control Station, formally abbreviated ANCS (abbreviated NC2 in WWII procedures), who has the following duties:[46]

• Assists the NCS to maintain optimum efficiency;
• Assumes NCS duties in event that the NCS develops station problems;
• Assumes NCS duties for a portion of the net, as directed or as needed;
• Serves as a resource for the NCS; echoes transmissions of the NCS if, and only if, directed to do so by the NCS;
• Maintains a duplicate net log

Nets can be described as always having a net opening and a net closing, with a roll call normally following the net opening, itself followed by regular net business, which may include announcements, official business, and message passing. Military nets will follow a very abbreviated and opaque version of the structure outlined below, but will still have the critical elements of opening, roll call, late check-ins, and closing.

A net should always operate on the same principle as the inverted pyramid used in journalism—the most important communications always come first, followed by content in ever lower levels of priority.

1. Net opening
   1. Identification of the NCS
   2. Announcement of the regular date, time, and frequency of the net
   3. Purpose of the net
2. Roll call
   1. A call for stations to check in, oftentimes from a roster of regular stations
   2. A call for late check-ins (stations on the roster who did not respond to the first check-in period)
   3. A call for guest stations to check in
3. Net business
4. Optional conversion to a free net
5. Net closing

Each net will typically have a main purpose, which varies according to the organization conducting the net, which occurs during the net business phase. For amateur radio nets, it's typically for the purpose of allowing stations to discuss their recent operating activities (stations worked, antennas built, etc.) or to swap equipment. For Military Auxiliary Radio System and National Traffic System nets, net business will involve mainly the passing of formal messages, known as radiograms.

Stations without the ability to acquire a time signal accurate to at least one second should request a time check at the start of every shift, or once a day minimum. Stations may ask the NCS for a time check by waiting for an appropriate pause, keying up and stating your call sign, and then using the prowords "REQUEST TIME CHECK, OVER" when the NCS calls on you. Otherwise, you may ask any station that has access to any of the above time signals for a time check.

Once requested, the sending station will state the current UTC time plus one minute, followed by a countdown as follows:

This is Net Control, TIME CHECK WUN AIT ZERO TOO ZULU (pause) WUN FIFE SECONDS…WUN ZERO SECONDS…FIFE FOWER TREE TOO WUN…TIME WUN AIT ZERO TOO ZULU…OVER

The receiving station will then use the proword "TIME" as the synch mark, indicating zero seconds. If the local time is desired instead of UTC, substitute the time zone code "JULIETT" for "ZULU".

Instead of providing time checks on an individual basis, the NCS should give advance notice of a time check by stating, for example, "TIME CHECK AT 0900 JULIETT", giving all stations sufficient time to prepare their clocks and watches for adjustment. A period of at least five minutes is suggested.

• Directed Net
  • A net in which no station other than the net control station can communicate with any other station, except for the transmission of urgent messages, without first obtaining the permission of the net control station.[47]
• Free net
  • A net in which any station may communicate with any other station in the same net without first obtaining permission from the net control station to do so.[47]

When calling stations who are part of a net, a variety of types of calls can be used:

The Civil Air Patrol and International Amateur Radio Union define a number of different nets which represent the typical type and range used in civilian radio communications:

U.S. Army Field Manual ACP 125(G) has the most complete set of procedure words used in radio nets:[50]

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.[51] 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:[52]

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:[53]

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.

(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.)[54]

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.

Station C21A (charlie-two-one Alpha) talking to C33B (charlie-three-three Bravo):[55]

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.