What is the ITU-R Morse standard?

ITU-R Recommendation M.1677-1 defines international Morse code: the dot and dash patterns for letters, digits, and punctuation, plus the timing rules. This tool uses that standard set rather than older American Morse variants.

A prosign is a procedural signal sent as a single run-together symbol with no gap between its letters. Examples are SOS (the distress call), AR (end of message), SK (end of contact), BT (a pause or new section), and BK (break).

How do I separate letters and words in Morse?

Put a single space between the code for each letter and three spaces, or a forward slash, between words. The decoder accepts either word separator and shows decoded words separated by a single space.

Why does SOS decode differently from S O S?

Sent as the prosign SOS the pattern is one continuous symbol with no internal gaps, dot-dot-dot-dash-dash-dash-dot-dot-dot, and the tool recognises it as the distress signal. Sent as three separate letters with gaps it decodes as the plain letters S, O, S.

Is my text processed locally?

Yes. Encoding and decoding use a built-in lookup table in your browser, so nothing you type is uploaded or stored anywhere.

What is the ITU-R Morse with Prosigns?

Encode and decode ITU-R international Morse code including letters, digits, punctuation and run-together prosigns such as SOS, AR, SK, BT and BK. Recognises prosigns on decode. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

ITU-R Morse with Prosigns

Name: ITU-R Morse with Prosigns
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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This tool encodes and decodes ITU-R international Morse code (ITU-R Recommendation M.1677-1) and, unlike a plain A-to-Z chart, correctly handles the prosigns — run-together procedural symbols used in real radio traffic: the distress call SOS, the end-of-message AR, the end-of-contact SK, the paragraph break BT, and the invitation to transmit KN. Type plain text to produce Morse; paste Morse to read it back.

ITU-R Morse: the standard

The ITU-R standard defines the dot-and-dash patterns for 26 letters, 10 digits, and the most common punctuation marks, plus the timing relationships between symbols. The pattern for each character is fixed and internationally standardised, so Morse from a Japanese station decodes identically to Morse from a Brazilian station.

How spacing carries the structure

In text Morse notation, the gaps between elements encode the boundaries between characters and words:

between dots/dashes in a character : no space (they run together)
between characters in a word       : single space
between words                      : three spaces (or a forward slash / )
prosign (SOS, AR, SK, BT, KN)     : characters run together with NO internal gap

The tool encodes by joining each character’s pattern with one space and each word with three spaces. On decode it splits the input on spacing first, then checks each gapless symbol block against the prosign table before the character table. Recognised prosigns appear in angle brackets: <SOS>, <AR>, <SK>.

Common prosigns and their meaning

Prosign	Pattern	Meaning in radio procedure
SOS	`...---...` (gapless)	International distress signal
AR	`.-.-.` (gapless)	End of message
SK	`...-.-` (gapless)	End of contact (sign off)
BT	`-...-` (gapless)	New paragraph or pause between message parts
KN	`-.--.` (gapless)	Invitation to transmit — specific station only

Ambiguities between prosigns and punctuation

Several prosigns share a dot-dash pattern with a punctuation character because in radio practice the context (position in a transmission) disambiguates them. .-.-. is both AR and the plus sign; -...- is both BT and the equals sign. The decoder reports the prosign when it matches a known prosign table entry; if you intend the punctuation mark rather than the prosign, note this in the context.

Worked example

Encoding the text SOS GERA produces ...---... --. . .-. .-. Decoding the gapless sequence ...---... returns <SOS>. Encoding AR as two separate characters gives . - .- .-. / .- — clearly different from the prosign. The output is plain text and copies cleanly into radio logs, training materials, or chat messages.