Prosigns for Morse code

Procedure signs or prosigns are shorthand signals used in Morse code radio telegraphy procedure, for the purpose of simplifying and standardizing radio communication protocol. They are several from Morse code abbreviations, which consist mainly of brevity codes that convey messages to other parties with greater speed and accuracy.

In general prosigns are just standardised parts of short form radio protocol, and can include any abbreviation. An example would be K for "okay, heard you, continue". In a more limited role the term refers to something akin to that of the nonprinting control characters in teleprinter and computer character sets, such as Baudot or 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 follow letter form. Many of them are longer than typical characters and are rendered without intercharacter commas or pauses. They are individual and indivisible code points within the broader Morse code, fully at par with basic letters.

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 procedure words for use in more recent voice protocols.

In printed material describing their meaning and use, prosigns are represented by either a sequence of dots and dashes for the sound of a telegraph, or by an overlined sequence of letters composed of International Morse Code, which if sent without the usual spacing, sounds like the prosign symbol. The most well-known example of the convention is the preamble to the standard distress call: SOS. As a prosign it is not really composed of the separate letters S, O and S, but is run together as a single symbol of   ▄ ▄ ▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄ ▄ ▄ ; it is a sign in its own right.

Not all prosigns are standardised. There are specialised variations of the coding convention used in certain radio networks to manage transmission and formatting of messages, and many conventions approximating prosigns but not quite being such exist. Such variants might not be unambiguous. One typical example of something which is not a recognized prosign but is yet recognizable is one or two freely timed dits at the end of a message, for OUT (the formal version being prosign AR, or   ▄ ▄▄▄ ▄ ▄▄▄ ▄ ) [1][2]

History

In the early decades of telegraphy, many efficiency improvements were incorporated into operations. The Morse code itself was one of these: it roughly coded more commonly used symbols into shorter keying sequences, and the rare ones into longer, thus leading to data compression online. The introduction of Morse symbols called procedure signs or prosigns was then just a logical progression. They were not defined by the inventors of Morse code, but were gradually introduced to improve the speed and accuracy of high-volume message handling, especially between professional telegraph operators operating over the time's long distance contacts, such as short wave radio and transatlantic cable.

Improvements to the legibility of formal written telegraph messages (telegrams) using white space formatting were thus supported by the creation of procedure symbols. Mastery of these Morse code prosigns was important in becoming an efficient telegraph operator, as was the command of many other forms of abbreviation.

Notation and representations

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

  1. Unique dot/dash sequences, e.g. (  ▄▄▄ ▄ ▄ ▄ ▄▄▄ ).
  2. Unique audible sounds, e.g. dah di di di dah
  3. Non-unique printed or written overlined character groups, e.g. BT (When overlining is not available, the same characters can be written in angle brackets <BT> or with underlining BT.)

Although some of the prosigns as-written appear to be simply two adjacent letters, most prosigns are transmitted as digraphs that have no spacing between the patterns that represent the "combined" letters, and are most commonly written with a single bar over the merged letters (if more than one single character) to indicate this.[3] The difference in the transmission is subtle, but the difference in meaning is gross. For example, the prosign AA (  ▄ ▄▄▄ ▄ ▄▄▄ ) indicates that the receiving Morse operator should space down one line, but the two separate letter sign or abbreviation AA (  ▄ ▄▄▄   ▄ ▄▄▄ ) indicates either the voice procedure words ALL AFTER, used to indicate that part of the previously transmitted message needs to be re-transmitted, or has the same meaning as the voice procedure word UNKNOWN STATION. The difference in representation between the Morse code prosign and the separate letter signs is the presence or absence of an inter-letter space between the two "dot dash" sequences.

Because there are no letter boundaries in the transmitted prosigns, their division into letters is arbitrary and may be done in multiple equivalent ways. For example, AA (  ▄ ▄▄▄ +  ▄ ▄▄▄ ) is exactly equivalent to EK (  ▄ +  ▄▄▄ ▄ ▄▄▄ ) and RT (  ▄ ▄▄▄ ▄ +  ▄▄▄ ). Likewise, the well-known prosign SOS could just as well be written VZE (  ▄ ▄ ▄ ▄▄▄ +  ▄▄▄ ▄▄▄ ▄ ▄ +  ▄ ), VGI (  ▄ ▄ ▄ ▄▄▄ +  ▄▄▄ ▄▄▄ ▄ +  ▄ ▄ ), or even 3B (  ▄ ▄ ▄ ▄▄▄ ▄▄▄ +  ▄▄▄ ▄ ▄ ▄ ). 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 (normally "=", but also "– –").[4] 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[2] or new section in a message heading.[4] When used as a prosign, there is no actual written or printed character representation or symbol for a new paragraph (i.e. no symbol corresponding to ""), other than the two-line white space itself.

Some prosigns are in unofficial use for special characters in languages other than English, for example "Ä" and AA, neither of which is part of the international standard.[4] Other prosigns are officially designated for both letters and prosigns, such as "+" and AR, which marks the end of a message.[lower-alpha 1][4] Some genuinely have only one use, such as CT or KA (  ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄ ), the International Morse prosign that marks the start of a new transmission[4] or new message.[2]

International Morse code

The procedure signs below are compiled from the official specification for Morse Code, ITU-R M.1677, International Morse Code,[4] while others are defined the International Radio Regulations, including ITU-R M.1170,[5] ITU-R M.1172,[3] and the International Code of Signals, with a few details of their usage appearing in ACP-131, which otherwise defines operating signals, not procedure signals.

General-use procedure signs
Prosign Matching voice procedure word Code symbol Defined in Explanation
DE THIS IS FROM   ▄▄▄ ▄ ▄   ▄  ITU-R M.1172[3] ITU-R M.1677-1[4] Used to precede the name or other identification of the calling station (Morse abbreviation).
AA UNKNOWN STATION   ▄ ▄▄▄ ▄ ▄▄▄  International Code of Signals[6] Used for directional signaling lights, but not in radiotelegraphy.
NIL NOTHING HEARD   ▄▄▄ ▄   ▄ ▄   ▄ ▄▄▄ ▄ ▄  General-purpose response to any request or inquiry for which the answer is "nothing" or "none" or "not available" (Morse abbr.). Also means "I have no messages for you."
R ROGER   ▄ ▄▄▄ ▄  ITU-R M.1172[3] Means the last transmission has been received, but does not indicate the message was understood or will be complied with.
K OVER   ▄▄▄ ▄ ▄▄▄  ITU-R M.1677-1[4] Invitation to transmit after terminating the call signal. (e.g.   ▄ ▄▄▄ ▄ ▄▄▄ ▄   ▄▄▄ ▄ ▄▄▄ ).
AR OUT   ▄ ▄▄▄ ▄ ▄▄▄ ▄  ITU-R M.1172[3] ITU-R M.1677-1[4] End of transmission / End of message / End of telegram.[lower-alpha 1]
(Same as EC "end copy", and character +.)[lower-alpha 2]
CL CLOSING   ▄▄▄ ▄ ▄▄▄ ▄   ▄ ▄▄▄ ▄ ▄  ITU-R M.1172[3] Announcing station shutdown (Morse abbr.).
CQ CALLING   ▄▄▄ ▄ ▄▄▄ ▄   ▄▄▄ ▄▄▄ ▄ ▄▄▄  ITU-R M.1172[3] General call to any station (Morse abbr.).
CP   ▄▄▄ ▄ ▄▄▄ ▄   ▄ ▄▄▄ ▄▄▄ ▄  ITU-R M.1172[3] General call to two or more specified stations (Morse abbr.).
CS   ▄▄▄ ▄ ▄▄▄ ▄   ▄ ▄ ▄  ITU-R M.1172[3] What is the name or identity signal of your station? (Morse abbr.)
AS WAIT   ▄ ▄▄▄ ▄ ▄ ▄  ITU-R M. 1170[8] ITU-R M.1172[3] ITU-R M.1677-1[4] "I must pause for a few minutes."[lower-alpha 3] Also means "I am engaged in a contact with another station [that you may not hear]; please wait quietly."
AS AR WAIT OUT   ▄ ▄▄▄ ▄ ▄ ▄   ▄ ▄▄▄ ▄ ▄▄▄ ▄  ACP 124 I must pause for more than a few minutes.
VE Verified   ▄ ▄ ▄ ▄▄▄ ▄  ITU-R M.1677-1[4] Message is verified.
WA WORD AFTER   ▄ ▄▄▄ ▄▄▄   ▄ ▄▄▄  ITU-R M.1172[3] (Morse abbr.)
WB WORD BEFORE   ▄ ▄▄▄ ▄▄▄   ▄▄▄ ▄ ▄ ▄  ITU-R M.1172[3] (Morse abbr.)
AA ALL AFTER   ▄ ▄▄▄   ▄ ▄▄▄  ITU-R M.1172[3] The portion of the message to which I refer is all that follows the text ... (Morse abbr.)
AB ALL BEFORE   ▄ ▄▄▄   ▄▄▄ ▄ ▄ ▄  ITU-R M.1172[3] The portion of the message to which I refer is all that precedes the text ... (Morse abbr.)
BN ALL BETWEEN   ▄▄▄ ▄ ▄ ▄   ▄▄▄ ▄  ITU-R M.1172[3] The portion of the message to which I refer is all that falls between ... and ... (Morse abbr.)
UD SAY AGAIN   ▄ ▄ ▄▄▄ ▄▄▄ ▄ ▄  ITU-R M.1677-1[4] ACP‑124[9] When standing alone, a note of interrogation or request for repetition of a transmission not understood. When ? is placed after a coded signal, modifies the code to be a question or request.
INT INTERROGATIVE   ▄ ▄ ▄▄▄ ▄ ▄▄▄  ACP124,[9] ACP‑131, Radiotelegraph Operations Guide[10] Military replacement for the ? prosign; equivalent to Spanish ¿ punctuation mark. When placed before a signal, modifies the signal to be a question/request.[11][lower-alpha 4]
HH CORRECTION

(KOR-REK-SHUN)

   ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄  ITU-R M.1677-1[4] Preceding text was in error. The following is the corrected text. (Same as EEEEEEEE.)
C CORRECT / AFFIRMATIVE   ▄▄▄ ▄ ▄▄▄ ▄  ITU-R M.1172[3] Answer to prior question is "yes". (Morse abbr.)
N NEGATIVE   ▄▄▄ ▄  International Code of Signals[6] ACP 131 Answer to prior question is "no". (Morse abbr.)[lower-alpha 5]
ZWF WRONG   ▄▄▄ ▄▄▄ ▄ ▄   ▄ ▄▄▄ ▄▄▄   ▄ ▄ ▄▄▄ ▄  Your last transmission was wrong. The correct version is ...
HH AR DISREGARD THIS TRANSMISSION; OUT   ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄   ▄ ▄▄▄ ▄ ▄▄▄ ▄  The entire message just sent is in error, disregard it. (Same as EEEEEEEE AR.)[lower-alpha 6]
QTR? REQUEST TIME CHECK   ▄▄▄ ▄▄▄ ▄ ▄▄▄    ▄▄▄    ▄ ▄▄▄ ▄    ▄ ▄ ▄▄▄ ▄▄▄ ▄ ▄  Time-check request. / What is the correct time?
(Time is always UTC, unless explicitly requested otherwise, e.g. QTR HST ?)
QTR TIME   ▄▄▄ ▄▄▄ ▄ ▄▄▄   ▄▄▄   ▄ ▄▄▄ ▄  The following is the correct UTC in HHMM 24-hour format
BT BREAK   ▄▄▄ ▄ ▄ ▄ ▄▄▄  ITU-R M.1172[3] ITU-R M.1677-1[4] Start new section of message.
Same as character = or – –.
BK BREAK-IN   ▄▄▄ ▄ ▄ ▄   ▄▄▄ ▄ ▄▄▄  ITU-R M.1172[3] Signal used to interrupt a transmission already in progress (Morse abbr.). AX in ACP131. In military networks TTTT or   ▄▄▄▄▄▄▄▄▄▄▄  is used instead.
KA ATTENTION   ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄  ITU-R M.1172[3] ITU-R M.1677-1[4] Message begins / Start of work / New message
(Starting signal that precedes every transmission. Sometimes written as CT.)
CFM I ACKNOWLEDGE   ▄▄▄ ▄ ▄▄▄ ▄   ▄ ▄ ▄▄▄ ▄   ▄▄▄ ▄▄▄  ITU-R M.1172[3] Message received (Morse abbr.). (Same as R.)
WX   ▄ ▄▄▄ ▄▄▄   ▄▄▄ ▄ ▄ ▄▄▄  ITU-R M.1172[3] Weather report follows (Morse abbr.).
INTERCO INTERCO

(IN-TER-CO)

 ITU-R M.1172[3] International Code of Signals groups follow (Morse abbr.).

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, but many of them do not have equivalents in any other definition of Morse code signals, including the ITU-R and Combined Communications Electronics Board telecommunications specifications.

Table of Morse code prosigns and useful Morse code abbreviations[1][4]
ProsignCode symbolMeaningCommentsVerbalizationAs text
AA  ▄ ▄▄▄ ▄ ▄▄▄ Start new lineSpace down one line; typewritten as Carriage Return, Line Feed (CR-LF).[2] Also written RT.di dah di dahÄ, Á[lower-alpha 7]
AR  ▄ ▄▄▄ ▄ ▄▄▄ ▄ Message separator, start new message / telegram.[4][1]New Page, space down several lines.[1] Decoder software may show "+".[4] Alternative for "Break" in conversational Morse.[2] Also written RN.di dah di dah dit+[4]
AS  ▄ ▄▄▄ ▄ ▄ ▄ Wait [4][1]Respond with: SN, or characters "R" (Received) or "C" (Confirmed).[1][4]di dah di di dit&[lower-alpha 8]
BT  ▄▄▄ ▄ ▄ ▄ ▄▄▄ Start of new section[4] / new paragraph.[1]Space down two lines; typewritten CR-LF-LF. Decoder software may show "=".[4]dah di di di dah=, – – [4]
CT  ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄ Start of transmission[4] Start of new message.[1]Attention[1] commencing transmission. Also written KA.dah di dah di dah 
HH  ▄ ▄ ▄ ▄ ▄ ▄ ▄ ▄ Error / correction[4][1]Always followed by correct text.[1] Sometimes transcribed as "????". Sometimes written EEEEEEEE.di di di di di di di dit 
K  ▄▄▄ ▄ ▄▄▄ Invitation for any station to transmit[4][1]Lone alphabetic character "K" at the end of a transmission.[1]dah di dahK[4]
 ?  ▄ ▄ ▄▄▄ ▄▄▄ ▄ ▄ Please say again[4][1]Lone question mark "?" from the receiving station in response to a transmission.[1]di di dah dah di dit?[4][1]
KN  ▄▄▄ ▄ ▄▄▄ ▄▄▄ ▄ Invitation for named station to transmit[1]Go ahead, specific named station.[1] Decoder software may show equivalent character "(".[4]dah di dah dah dit( [4]
NJ  ▄▄▄ ▄ ▄ ▄▄▄ ▄▄▄ ▄▄▄ Shift to Wabun codeShift from Morse code to Wabun code Kana characters. Also written XM.dah di di dah dah dah 
SK  ▄ ▄ ▄ ▄▄▄ ▄ ▄▄▄ End of contact[1] / End of work[4]Also written VA.di di di dah di dah 
SN  ▄ ▄ ▄ ▄▄▄ ▄ Understood.[1] Verified.[4]Message received and checks okay. Alternatively shift from Wabun to Morse code. "SN?" verification requested. Also written VE.di di di dah ditŠ, Ś[lower-alpha 7]
SOS  ▄ ▄ ▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄ ▄ ▄ Start of distress signal[4][1]Only used by original message sender, and only for imminent danger to life or property.[4] (listen )di di di dah dah dah di di dit 
BK  ▄▄▄ ▄ ▄ ▄   ▄▄▄ ▄ ▄▄▄ Break in conversation[1]Morse abbreviation for "back-to you" (Morse abbr.).[1] In conversational Morse some use either AR, BT, KN, or "K" instead.dah di di dit   da di dahBK
CL  ▄▄▄ ▄ ▄▄▄ ▄   ▄ ▄▄▄ ▄ ▄ Closing down[1]Abbreviation for "closing station" (Morse abbr.).dah di dah dit   di dah di ditCL

Obsolete prosigns
Historical Morse code prosigns
Prosign Matching Voice Procedure Word Former Code Symbol Explanation Defined in
VE General call   ▄ ▄ ▄ ▄▄▄ ▄  Code re-used for "Message verified" or "Message understood" (see SN above). 1937 Royal Navy Signal Card[12][13]
NNNNN Answering sign   ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄ ▄ 
ii Separative sign break   ▄ ▄   ▄ ▄  Generally replaced by BT, although it is still used in MARS CW operations.[10] This prosign was also defined in ACP‑124, "Communication Instructions Radio Telegraph Procedure"[9]
EEEEE Erase sign   ▄ ▄ ▄ ▄ ▄  Exactly five dots (code for numeral 5). Replaced by EEEEEEEE (exactly eight, HH).
RRRRR Receipt sign ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ Replaced by R.
e Further message sign   ▄ ▄ ▄▄▄ ▄ ▄  Re-purposed original ITU symbol for É not used in English.

See also

Notes
  1. AR was used to mark the end of individual telegrams within a batched-message.
  2. As of 2017 the is a proposal that (perhaps inadvertently) changes AR protocol.[7]
  3. AS may optionally be followed by the estimated number of minutes of waiting time.
  4. 1945 procedural use: "The correctness of a short portion of a message may be questioned directly by the receiving operator using the interrogatory prosign INT, but this method should not be used to question a part of a message for which a receipt has been given.[11]
  5. When Morse was still being used in aeronautics, the entire word NO (  ▄▄▄ ▄   ▄▄▄ ▄▄▄ ▄▄▄ ) was sent instead of the abbreviation N.
  6. The prowords HH AR may not be used to cancel a message after it has already been completely transmitted, and receipt acknowledged.
  7. Non-ITU Code adopted nationally for languages with letters not used in Latin, English, or Italian.
  8. Proposed double-use as punctuation ampersand; non-standard. Abbreviation "E S" is typically used instead.

References
  1. ARRL Operating Manual (10 ed.). Newington, CT: American Radio Relay League. 8 October 2012. ISBN 978-0872595965.
  2. Chapter 3: Sending messages in CW (PDF). ARRL network reference. Newington, CT: American Radio Relay League. 25 September 2002.
  3. Miscellaneous abbreviations and signals to be used for radiocommunications in the maritime mobile service. Radiocommunication Sector. ITU.int (Report). ITU Recommendation. Geneva, CH: International Telecommunication Union. ITU-R M.1172.
  4. International Morse Code. Radiocommunication Sector (Report). ITU Recommendation. Geneva, CH: International Telecommunication Union. October 2009. ITU-R M.1677-1.
  5. Morse telegraphy procedures in the maritime mobile service (PDF). Radiocommunication Sector. ITU.int (Report). ITU Recommendation. Geneva, CH: International Telecommunication Union. March 2012. ITU-R M.1170-1.
  6. "International Code of Signals" (PDF). SeaSources.net (1969 (reaffirmed 2003) ed.).
  7. "Resolution on conflicting CW procedure" (PDF).
  8. "Morse telegraphy procedures in the maritime mobile service" (PDF). ITU.int. ITU Recommendations. Geneva, CH: International Telecommunication Union. ITU-R M.1170-1.
  9. "Communication Instructions Radio Telegraph Procedure" (PDF). Navy-Radio. ACP124.
  10. "Radiotelegraph Operations Guide" (PDF). QSL.net. May 2009.
  11. United States War Department (1945). Radio Operator's Manual. Field Manual. Fort Monroe, VA: Army Field Printing Plant, CAS. FM24-6.
  12. "1937 Royal Navy Signal Card". 1937.
  13. "Signal Card".
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