Prosigns for Morse code

Procedural signs or prosigns are shorthand signals used in Morse code telegraphy, for the purpose of simplifying and standardizing procedural protocols for landline and radio communication. The procedural signs are distinct from conventional Morse code abbreviations, which consist mainly of brevity codes that convey messages to other parties with greater speed and accuracy. However, some codes are used both as prosigns and as single letters or punctuation marks, and for those, the distinction between a prosign and abbreviation is ambiguous, even in context.

Overview

In the broader sense prosigns are just standardised parts of short form radio protocol, and can include any abbreviation. Examples would be ' for "okay, heard you, continue" or ' for "message, received". In a more restricted sense, "prosign" refers to something analogous to the nonprinting control characters in teleprinter and computer character sets, such as Baudot and ASCII. Different from abbreviations, those are universally recognizable across language barriers as distinct and well-defined symbols.
At the coding level, prosigns admit any form the Morse code can take, unlike abbreviations which have to be sent as a sequence of individual letters, like ordinary text. On the other hand, most prosigns codes are much longer than typical codes for letters and numbers. They are individual and indivisible code points within the broader Morse code, fully at par with basic letters and numbers.
The development of prosigns began in the 1860s for wired telegraphy. Since telegraphy preceded voice communications by several decades, many of the much older Morse prosigns have acquired precisely equivalent prowords for use in more recent voice protocols.
Not all prosigns used by telegraphers are standard: There are regional and community-specific variations of the coding convention used in certain radio networks to manage transmission and formatting of messages, and many unofficial prosign conventions exist; some of which might be redundant or ambiguous. One typical example of something which is not an officially recognized prosign, but is yet fairly often used in Europe, is one or two freely timed dits at the end of a message, or ; it is equivalent to the proword OUT, meaning "I'm done; go ahead". However the official prosign with the same meaning is, or, which takes a little longer to send.

Representation in printed material

Even though represented as strings of letters, prosigns are rendered without the intercharacter commas or pauses that would occur between the letters shown, if the representation were sent as a sequence of letters: In printed material describing their meaning and use, prosigns are shown either as a sequence of dots and dashes for the sound of a telegraph, or by an overlined sequence of letters from the International Morse Code, which when sent without the usual spacing, sounds like the prosign symbol.
The best-known example of the convention is the standard distress call preamble: [SOS|]. As a prosign it is not really composed of the three separate letters S, O, and S, but is run together as a single symbol, which is a sign in its own right.

History

In the early decades of telegraphy, many efficiency improvements were incorporated into operations. Each of the early versions of Morse code was an example of that: With only one glaring exception, they all encoded more common characters into shorter keying sequences, and the rare ones into longer, thus effecting online data compression. The introduction of Morse symbols called procedural signs or prosigns was then just a logical progression. They were not defined by the developers of Morse code, but were gradually introduced by telegraph operators to improve the speed and accuracy of high-volume message handling, especially those sent over that era's problematic long distance communication channels, such as transoceanic cables and later longwave wireless telegraphy.
Among other prosign uses, improvement in the legibility of written messages sent by telegraph using white space formatting was supported by the procedural symbols. To become an efficient telegraph operator it was important to master the Morse code prosigns, as well as the many standard abbreviations used to facilitate checking and re-sending sections of text.

Notation and representations

There are at least three methods used to represent Morse prosign symbols:

Unique dot/dash sequences, e.g.
Unique audible sounds, e.g. dah di di di dah
Non-unique printed or written overlined character groups, e.g. '

Although some of the prosigns as-written appear to be simply two adjacent letters, most prosigns are transmitted as digraphs that have no pauses between the patterns that represent the "combined" letters, and are most commonly written with a single bar over the merged letters to indicate this. The only difference between what is transmitted for the Morse code prosign vs. the separate letter signs is the presence or absence of an inter-letter space between the two "dit" / "dah" sequences.
Although the difference in the transmission is subtle, the difference in meaning is gross:
Because no letter boundaries are transmitted with the codes counted as prosigns, their representation by two letters is usually arbitrary, and may be done in multiple equivalent ways. Normally, one particular form is used by convention, but some prosigns have multiple forms in common use:
Many Morse code prosigns do not have written or printed textual character representations in the original source information, even if they do represent characters in other contexts. For example, when embedded in text the Morse code sequence represents the "double hyphen" character. When the same code appears alone it indicates the action of spacing down two lines on a page in order to create the white space indicating the start of a new paragraph or new section in a message heading. When used as a prosign, there is no actual written or printed character representation or symbol for a new paragraph, other than the two-line white space itself.
Some prosigns are in unofficial use for special characters in languages other than English, for example is used unofficially for both the "next line" prosign and for "'", neither of which is in the international standard. Other prosigns are officially designated for both characters and prosigns, such as equiv. "+", which marks the end of a message. Some genuinely have only one use, such as or the equivalent, the International Morse prosign that marks the start of a new transmission or new message.

International Morse code

The procedure signs below are compiled from the official specification for Morse Code, ITU-R M.1677, International Morse Code, while others are defined the International Radio Regulations for Mobile Maritime Service, including ITU-R M.1170, ITU-R M.1172, and the Maritime International Code of Signals, with a few details of their use appearing in ACP 131, which otherwise defines operating signals, not procedure signals.

Prosigns

The following table of prosigns includes ' and ', which could be considered either abbreviations or prosigns that are also letters. All of the rest of the symbols are not letters, but in some cases are also used as punctuation.

Prosign	Matching voice procedure word	Code symbol	Reference	Explanation
'	UNKNOWN STATION			This meaning is only used for directional signal lights. It has no official use in radio telegraphy, where it is unofficially used to represent an accented letter ' or ', or the prosign for "next line", and then only when it is embedded inside a heading section in amateur traffic.
R	ROGER			Means the last transmission has been received, but does not necessarily indicate the message was understood or will be complied with.
K	OVER			Invitation to transmit after terminating the call signal..
'	OUT			End of transmission / End of message / End of telegram.
'	WAIT			"I must pause for a few minutes." Also means "I am engaged in a contact with another station ; please wait quietly."
'	WAIT ''OUT			I must pause for more than a few minutes.
'	VERIFIED			Message is verified.
	SAY AGAIN?			When standing alone, a note of interrogation or request for repetition of the immediate prior transmission that was not understood. When is placed after a coded signal, modifies the code to be a question or request.
'	INTERROGATIVE			Military replacement for the prosign; equivalent to Spanish ¿\| punctuation mark. When placed before a signal, modifies the signal to be a question/request.
'...	CORRECTION			Preceding text was in error. The following is the corrected text.
'	DISREGARD THIS TRANSMISSION OUT			The entire message just sent is in error, disregard it.
'	BREAK			Start new section of message. Same as character or rarely .
'	ATTENTION			Message begins / Start of work / New message
	OUT''			End of contact / End of work / Line is now free /

Abbreviations for message handling

The following table lists standard abbreviations used for organizing radiotelegraph traffic, however none of them are actual prosigns, despite their similar purpose. All are strictly used as normal strings of one to several letters, never as digraph symbols, and have standard meanings used for the management of sending and receiving messages. Dots following indicate that in use, the abbreviation is always followed by more information.

Abbrev.	Matching voice procedure word	Code symbol	Reference	Explanation
DE...	FROM			Used to precede the name or other identification of the station sending the transmission.
NIL	NOTHING HEARD			General-purpose response to any request or inquiry for which the answer is "nothing" or "none" or "not available". Also means "I have no messages for you."
CL	CLOSING			Announcing station shutdown.
CQ	CALLING			General call to any station.
CP......	CALLING FOR			Specific call to two or more named stations.
CS...	CALLING STATION			Specific call to exactly one named station.
CS ?	WHO ?			What is the name or identity signal of your station? In many contexts, the question mark is optional.
WA...	WORD AFTER
WB...	WORD BEFORE
AA...	ALL AFTER			The portion of the message to which I refer is all that follows the text...
AB...	ALL BEFORE			The portion of the message to which I refer is all that precedes the text...
	ALL BETWEEN			The portion of the message to which I refer is all that falls between... and...
C	CORRECT / YES / AFFIRMATIVE / CONFIRM			Answer to prior question is "yes".
N	NO / NEGATIVE			Answer to prior question is "no".
ZWF...	WRONG			Your last transmission was wrong. The correct version is...
QTR ?	REQUEST TIME CHECK			Time-check request. / What is the correct time?
QTR...	TIME IS			The following is the correct time in HHMM 24 hour format
BK	BREAK-IN			Signal used to interrupt a transmission already in progress. NATO nets use '. Some military networks use instead.
CFM	CONFIRM / I ACKNOWLEDGE			Message received.
WX...	WEATHER IS			Weather report follows.
'	INTERCO			Groups of abbreviations from the International Code of Signals follow.

Amateur radio National Traffic System

For the special purpose of exchanging ARRL Radiograms during National Traffic System nets, the following prosigns and signals can be used, most of which are an exact match with ITU-R and Combined Communications Electronics Board standards; a few have no equivalent in any other definition of Morse code procedure signals or abbreviations.