The armed forces of the NATO countries have similar procedures in order to make cooperation easier.
These procedures have been developed, tested under the most difficult of conditions, then revised to implement the lessons learned, many times since the early 1900s[clarification needed].
According to ACP 125(G)[2] and the Virginia Defense Force Signal Operating Instructions:[4]Voice procedure is designed to provide the fastest and most accurate method of speech transmission.
Regulations created by the FCC are codified in Title 47 of the Code of Federal Regulations: Radio call signs are a globally unique identifier assigned to all stations that are required to obtain a license in order to emit RF energy.
The recommended techniques vary, but generally align with the following guidelines, which are extracted from the IARU Emergency Telecommunications Guide[8]
Similarly, the U.S. military radio procedures recommend headsets with noise-cancelling microphones:Use of Audio Equipment.
The California Statewide EMS Operations and Communications Resource Manual explains why:Key your transmitter before engaging in speech.
Pausing one second after depressing the push-to-talk button on the microphone or handset is sufficient in most cases to prevent missed words or responses.
In addition to cutting off important audio bandwidth at both the low and high ends of the human speech spectrum (reducing the bandwidth by at least half), other distortions of the voice occur in the microphone, transmitter, receiver, and speaker—and the radio signal itself is subject to fading, interruptions, and other interference.
All of these make human speech more difficult to recognize; in particular, momentary disruptions or distortions of the signal are likely to block the transmission of entire syllables.
[12] Several radio operation procedures manuals, including ACP 125(G) teach the same mnemonic of Rhythm, Speed, Volume, and Pitch (RSVP):[13] According to the UK's Radiotelephony Manual, CAP 413, radio operators should talk at a speed of fewer than 100 words per minute.
Voice communications procedures for international air traffic control and communications among airplanes are defined by the following International Civil Aviation Organization documents: Refinements and localization of these procedures can be done by each member country of ICAO.
The March, 1940 issue of The APCO Bulletin explains the origin of this order was found to have better results than other methods,[36] Stations needing to interrupt other communications in-progress shall use the most appropriate of the below procedure words, followed by their call sign.
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).
The most complete set of procedure words is defined in the U.S. Military's Allied Communications Publication ACP 125(G).
In the tables below, the mappings of the QSA and QRK Morse code prosigns is interpreted because there is not a 1:1 correlation.
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.
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".
[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.
When practicable, messages relating to schedules will be transmitted by a means of signal communication other than radio.
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.
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.
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.
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 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").
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!
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!
(*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.