The NATO communications manual ACP-125[2] 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,[3] the U.S. Coast Guard,[4] US Civil Air Patrol,[5] US Military Auxiliary Radio System,[6] and others.
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".
With spring-loaded Push to talk (PTT) buttons on modern combined transceivers, the same meaning can be communicated with just "OUT", as in "Ops, Alpha, ETA five minutes.
Example: "ROGER" may be used to mean "yes" with regard to confirming a command; however, in Air Traffic Control phraseology, it does not signify that a clearance has been given.
[citation needed] 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".
Example: radio working between Solent Coastguard and a motor vessel, call-sign EG 93, where part of the initial transmission is unintelligible.
"[citation needed] "I must pause for longer than a few seconds.." "Please repeat my entire transmission back to me.
"[citation needed] The sender requests a response indicating the strength and readability of their transmission, according to plain language radio check standards: "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.
Example of correct US Army radio check, for receiver A-11 (Alpha 11) and sender D-12 (Delta 12): 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.
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".
OverVHF 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.
After that pilot can give, or the controller can ask for, additional information, such as, fuel and number of passengers on board.
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]
Indicates that complete radio silence is no longer required and restricted (limited) use of the frequency may resume, but immediately giving way to all further distress communications.
ICAO defines a very similar but shorter list of prowords in Annex 10 of its Radiotelephony Procedures (to the Convention on International Civil Aviation).
Beginning in 2001, large vessels, defined as being 500 gross tonnage or greater, the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers has required that a restricted and simplified English vocabulary with pre-set phrases, called Standard Marine Communication Phrases (SMCP), be used and understood by all officers in charge of a navigational watch.
The aim is to get round the problem of language barriers at sea and avoid misunderstandings which can cause accidents.
Instead, it consists of entire pre-formed phrases carefully designed for each situation, and watch officers must pass a test of their usage in order to be certified under international maritime regulations.
Because over a poor quality connection the words "affirmative" and "negative" can be mistaken for one another (for example over a sound-powered telephone circuit), United States Navy instruction omits the use of either as prowords.