Procedure words (abbreviated to prowords) are words or phrases limited to radiotelephony procedure used to facilitate communication by conveying information in a condensed standard verbal format. Prowords are voice versions of the much older procedural signs for Morse code which were first developed in the 1860s for Morse telegraphy, and their meaning is identical.
The NATO communications manual ACP-125 contains the most formal and perhaps earliest modern (post-World War II) glossary of prowords, but its definitions have been adopted by many other organizations, including the United Nations Development Programme, the U.S. Coast Guard, US Civil Air Patrol, US Military Auxiliary Radio System, and others.
Prowords are one of several structured parts of radio voice procedures, including brevity codes and plain language radio checks.
Examples According to the U.S. Marine Corps training document FMSO 108, "understanding the following PROWORDS and their respective definitions is the key to clear and concise communication procedures".
This is ... This transmission is from the station whose designator immediately follows. For clarity, the station called should also be named, before the station calling. For example, "Victor Juliet zero, this is Golf Mike Oscar three...," or for brevity, "Victor Juliet zero, Golf Mike Oscar three...." The reverse ("This is GMO3 calling VJ0") is never allowed.
Over "This is the end of my transmission to you and a response is necessary. Go ahead: transmit."
Out "This is the end of my transmission to you, and no answer is required or expected."
"Over" and "Out" are never used at the same time, as their meanings are mutually exclusive.
Do you read? A question about whether the receiver can hear and understand the transmission.
Example: "Bob, you read me? What is the situation from your position?"
Example:
Roger "ROGER" may not be used to mean "yes" with regard to confirming a command; in Air Traffic Control phraseology, it does not signify that a clearance has been given. The term originates from the practice of telegraphers sending an "R" to stand for "received" after successfully getting a message. This was extended into spoken radio during World War II, with the "R" changed to the spelling alphabet equivalent word "Roger". The modern NATO spelling alphabet uses the word "Romeo" for "R" instead of "Roger", and "Romeo" is sometimes used for the same purpose as "Roger", mainly in Australian maritime operations.
Wilco "I understand and will comply." It is used on receipt of an order. "Roger" and "Wilco" used together (e.g. "Roger, Wilco") are redundant, since "Wilco" includes the acknowledgement element of "Roger".
Say again "I have not understood your message, please SAY AGAIN". Usually used with prowords "ALL AFTER" or "ALL BEFORE". Example: radio working between Solent Coastguard and a motor vessel, call-sign EG 93, where part of the initial transmission is unintelligible.
Example:
At this juncture, Solent Coastguard would reply, preceding the message with the prowords "I SAY AGAIN":
The word "REPEAT" should not be used in place of "SAY AGAIN", especially on artillery fire control nets, as "REPEAT" is an artillery proword defined in ACP 125 U.S. Supp-2(A) with the wholly different meaning of "request for the same volume of fire to be fired again with or without corrections or changes" (e.g., at the same coordinates as the previous round).
All after... "Please repeat the message you just sent me beginning after the word or phrase said after this proword."
Example:
At this juncture, Solent Coastguard would reply, preceding the message after "position" with the prowords "I SAY AGAIN":
All before... "Please repeat the message you just sent me ending before the word or phrase said after this proword."
Wait over "Wait for some time."
Standby "I must pause for a few seconds."
Wait out "I must pause for longer than a few seconds.."
Read back "Please repeat my entire transmission back to me."
I read back "The following is my response to your READ BACK proword."
Correction "I made an error in this transmission. Transmission will continue with the last word correctly sent."
Radio check "What is my signal strength and readability; how do you hear me?"
The sender requests a response indicating the strength and readability of their transmission, according to plain language radio check standards: A response of ROGER is shorthand for the prowords LOUD AND CLEAR. A response of WEAK BUT READABLE ("WEAK READABLE" is also used) indicates a weak signal but I can understand. A response of WEAK AND DISTORTED indicates a weak signal and unreadable. A response of STRONG BUT DISTORTED indicates a strong signal but unreadable. One of the two stations might be slightly off frequency, there might be multipath distortion, or there might be a problem with the audio circuits on one or both of the radios.
"5 by 5" is an older term used to assess radio signals, as in 5 out of 5 units for both signal strength and readability. Other terms similar to 5x5 are "LOUD AND CLEAR" or "Lima and Charlie". Example:
Similar example in shorter form:
If the initiating station (Alpha 12 in the example) cannot hear the responding station (X-ray 23 above), then the initiator attempts a radio-check again, or if the responder's signal was not heard, the initiator replies to the responder with "Negative contact, Alpha 12 OUT".
The following readability scale is used: 1 = bad (unreadable); 2 = poor (readable now and then); 3 = fair (readable, but with difficulty); 4 = good (readable); 5 = excellent (perfectly readable).
Example of correct US Army radio check, for receiver A-11 (Alpha 11) and sender D-12 (Delta 12):
Article 32 Radio Regulations distress and rescue International Telecommunication Union (ITU) Radio Regulations and the International Civil Aviation Organization (ICAO) Convention and Procedures for Air Navigation Services set out "distress, urgency and safety procedures".
On the radio, distress (emergency) and rescue usage takes precedence above all other usage, and the radio stations at the scene of the disaster (on land, in a plane, or on a boat) are authorized to commandeer the frequency and prohibit all transmissions that are not involved in assisting them. These procedure words originate in the International Radio Regulations.
The Combined Communications-Electronics Board (representing military use by Australia, Canada, New Zealand, United Kingdom and United States) sets out their usage in the Allied Communications Publications "ACP 135(F) Communications instructions Distress and Rescue Procedures".
Mayday
Mayday is used internationally as the official SOS/distress call for voice. It means that the caller, their vessel or a person aboard the vessel is in grave and imminent danger, send immediate assistance. This call takes priority over all other calls.
The correct format for a Mayday call is as follows:
[The first part of the signal is known as the "call"]
Mayday, Mayday, Mayday This is (vessel name repeated three times, followed by call sign if available)
[The subsequent part of the signal is known as the "message"]
Mayday (vessel name) My position is (position as a lat-long position or bearing and distance from a fixed point) I am (type of distress, e.g. on fire and sinking) I require immediate assistance I have (number of people on board and their condition) (Any other information e.g. "I am abandoning to life rafts") Over
VHF instructors, specifically those working for the Royal Yachting Association, often suggest the mnemonic MIPDANIO for learning the message of a Mayday signal: mayday, identify, position, distress, assistance, number-of-crew, information, over.
In aviation a different format is used:
[First part of the message] Mayday, Mayday, Mayday [Second part of the message] Callsign [Third part of the message] Nature of the emergency
For example: "Mayday, Mayday, Mayday, Wiki Air 999, we have lost both of our engines due to a bird strike, we are gliding now."
After that the pilot can give, or the controller can ask for, additional related information such as fuel conditions, number of passengers on board, and so on.
Pan-Pan
Pan-pan (pronounced ) is the official urgency voice call.
Meaning "I, my vessel, or a person aboard my vessel, require, or requires, assistance, but am, or is, not in distress." This overrides all but a mayday call, and is used, as an example, for calling for medical assistance or if the station has no means of propulsion. The correct usage is:
Pan-Pan, Pan-Pan, Pan-Pan All stations, all stations, all stations This is [vessel name repeated three times] My position is [position as a lat-long position or bearing and distance from a fixed point] I am [type of urgency, e.g. drifting without power in a shipping lane] I require [type of assistance required] [Any other information e.g. size of vessel, which may be important for towing] Over
SÉCURITÉ
Pronounced , this is the official safety voice call.
"I have important meteorological, navigational or safety information to pass on." This call is normally broadcast on a defined channel (channel 16 for maritime VHF) and then moved onto another channel to pass the message. Example:
[On channel 16]
SÉCURITÉ, SÉCURITÉ, SÉCURITÉ
All stations, all stations, all stations.
This is Echo Golf niner three, Echo Golf niner three, Echo Golf niner three.
For urgent navigational warning, listen on channel six-seven.
OUT
[Then on channel 67]
SÉCURITÉ, SÉCURITÉ, SÉCURITÉ
All stations, all stations, all stations.
This is Echo Golf niner tree (three), Echo Golf niner tree, Echo Golf niner tree.
Floating debris sighted off Calshot Spit.
Considered a danger to surface navigation.
OUT
SEELONCE MAYDAY "Seelonce" is an approximation rendition of the French word silence and indicates that your vessel has an emergency and that you are requiring radio silence from all other stations not assisting you.
SEELONCE DISTRESS Indicates that you are relaying or assisting a station that has placed a MAYDAY call and you are requiring radio silence from all other stations not assisting you or the station in distress.
When the emergency issue is winding down or nearly resolved, the two subsequent prowords (below) are used to open up the frequency for use by stations not involved in the emergency:
PRU-DONCE From the French word prudence and indicates that complete radio silence is no longer required and restricted (i.e., limited) use of the frequency may resume, but must still immediately give way in the event of further distress communications.
SEELONCE FEENEE From the French word silence and fini (ended) and indicates that emergency communications have ceased and normal use of the frequency may resume.
ACP 125(F)