Morse Code Prosigns — AR, SK, BT, KN, AS and the Complete List

What exactly is a prosign?

The defining feature is not the meaning — it is the fusion. Take AR. Sent as ordinary text, "A R" is .- then a three-unit letter gap then .-. — two rhythms with a silence in the middle. Sent as the prosign, it is .-.-. keyed as one continuous run: five elements with only one-unit gaps inside, a single gesture of the hand. Same dots and dashes; an entirely different character. On the air the difference is unmistakable — the prosign has no seam.

Fusion does real work. A fused signal is *shorter* than its letters (the inter-letter gaps are deleted), so it arrives faster — useful for the most-used control signals. It is also rhythmically unlike any real letter, so it can't be mistaken for text: no letter of the alphabet has AR's five-element shape, which means .-.-. can only ever mean one thing. Procedure and content never collide.

One boundary case to file early: single-letter control signals like K (-.-, *go ahead*) are procedural signals by function but are not *fused* — there's nothing to fuse. Purists call those "procedure signals" and reserve "prosign" for the multi-letter fused forms; on this page both are listed, with the distinction marked.

How prosigns are written: the overline and the copy marks

Ordinary typography has no way to write "letters sent with no gap," so print notation solves it with a bar: the letters of a prosign are written together with an overline above them — A̅R̅, S̅K̅, B̅T̅, K̅N̅, A̅S̅. The bar is not decoration; it is the fusion made visible, and it is the standard you'll see in ITU texts, military message manuals, and serious references.

Operators copying traffic by hand invented their own shorthand centuries back, and it survives in logs and some software: the marks that were quick to write and unambiguous to reread. You will still see AR rendered as `+`, BT as `=`, and SK as `VA` in copied text. When an old log shows ...UR 599 599 = NAME HR = ...+, those symbols are prosigns wearing work clothes.

A third notation lives in software: the angle-bracket form. Because a keyboard can't overline anything either, CW applications — decoders, keyers, logging programs, contest engines — accept <AR>, <SK>, <BT>, <AS>, <KN>, <HH> in typed text and send them fused. The translator uses the same convention. Three notations, one meaning, and now you can read all of them.

The complete prosign table

Everything you will meet on the air and in message-handling manuals, in the order you are likely to need it. "Written" shows the overline form (with the plain spelling in parentheses); "Copy mark" is the handwritten shorthand from the logging tradition.

The sending rule: fused inside, spaced outside

Prosigns obey one spacing law, and it has two halves. Inside the prosign: no gaps at all — the letters lose their three-unit separation and merge into a single character with only the normal one-unit joins between elements. Outside the prosign: normal letter spacing — three units of silence before and after, exactly as if the prosign were an ordinary letter sitting in the text. MSG FER U AR K is sent as M-S-G … F-E-R … U … AR … K, with standard gaps at every boundary.

This is the detail beginners get wrong in both directions. Keying AR with a letter gap in the middle sends the *letters* A and R — which the receiving operator reads as text, and waits politely for the sentence to continue. Keying AR then *immediately* the next word with no gap fuses it into a phantom mega-character that decodes as nothing. The rule is simple to say and worth practicing slowly: fuse the inside, space the outside.

Two special cases. SOS is always sent fused, all nine elements as one character — that gaplessness is part of what makes it recognizable through noise (the full story is on the SOS page). And HH has no letters to fuse: it is literally eight dots in a row, one-unit gaps throughout — the only prosign whose pattern could never be confused with anything, which is the point.

K, KN, AR, SK: turn management in one real contact

The invitation-and-closing family is where prosigns stop being trivia and become conversation. Watch them work in a minimal but complete CW contact:

• CQ CQ CQ DE W1AW W1AW K — the calling station ends with plain K: *anyone* may answer.
• W1AW DE OH2AA OH2AA KN — the caller answers *one specific station* with KN: everyone else stands down. Two letters of rhythm doing the work of a paragraph of etiquette.
• …name Esko, QTH Helsinki… BT …rig 5W… AR W1AW DE OH2AA K — inside the message, BT marks paragraphs; AR declares the message complete and passes the turn, with plain K reopening the floor to anyone.
• …73. W1AW DE OH2AA SK — and finally SK: *this contact is finished* — not just this message. Anyone tuning past knows the frequency frees up.

Making mistakes: HH and the correction ritual

Every operator, in every era, has sent the wrong letter mid-word. The protocol is the same one the wire telegraphers used. Send HH — eight quick dots — the instant you know; it means *erase that, correction follows*. Then back up to a clean boundary (the last word, or the last BT), and send the corrected text again. In printed form the sequence looks like: NAME HR IS ESK HH ESKO — "scratch that E, the name is ESKO."

The etiquette around HH is unstrict and humane: nobody scores you on mistakes, only on *unacknowledged* mistakes. A clean HH and a resend cost three seconds; a botched word left standing costs the other operator a fill request and both of you a round trip. Old operators' advice still holds: send your HH with the same rhythm you'd send anything else — the frantic skitter of eight dots is one of the most human sounds on any band, and there is no reason to make it more frantic than it needs to be.

One sibling worth knowing: if you need the *other* station to repeat something, the request is plain language or an abbreviation (AGN? — again), not a prosign. HH polices your own sending; requests police theirs. The division of labor is absolute, and getting it right is half of sounding like an operator rather than a student.

How prosigns relate to punctuation and Q-codes

Three layers of "not ordinary text" circulate in a CW contact, and they are different species. Punctuation marks (comma --..--, period .-.-.-, question mark ..--..) belong to the *text* — they're sent with normal letter spacing and carry the sentence's own grammar; the full set lives on the punctuation reference. Prosigns punctuate the *transmission* — a period ends a sentence, but AR ends the message; a comma marks a clause, but BT marks a paragraph of the operating flow. Q-codes compress standard *phrases* — QTH isn't structure, it's a whole sentence riding three letters.

The cleanest test for which layer you're looking at: does it bind text together or manage the channel? Question mark, comma — text. BT, AR, KN — channel. QTH, QRM, QSB — content, abbreviated. One contact uses all three layers constantly, and fluent operators hear them as separate *voices*: the message, the operator's control gestures, and the standard phrase-book, interleaved.

There is one deliberate crossover: BT doubles as a paragraph mark inside message text, which is why transcribers render it as = — an equals sign is exactly what a paragraph separator wants to be on paper. And SOS, the most famous signal in radio, is formally a prosign — procedure at the highest possible stakes. Layers exist to be used, not to be walls.

How to train your ear for fused characters

You cannot learn fusion from a chart, because fusion exists only in time. What works is the same sound-first discipline that builds the letters: hear the prosigns at full speed, in context, until each arrives as one shape. The fastest exercise costs two minutes: type a micro-contact into the translator — CQ CQ DE W1AW K W1AW DE OH2AA KN — play it at 15 WPM, and listen specifically for the seams. Letters have seams; prosigns don't.

Then drill the minimal pairs the ear actually confuses. AR (.-.-.) versus the letters A-R (.- gap .-.) is the classic — the prosign is one continuous glide, the letters are two beats with a hole between. The same drill covers KN versus K-N and AS versus A-S. Ten reps of each pair per day for a week is enough; the distinction isn't subtle once your ear has been pointed at it, it's only *invisible* before.

Finally, graduate to real material. The structured progression on the learn hub adds the procedural layer after the alphabet precisely because order matters; the quiz and Koch trainer harden the letters underneath. The arrival moment is unmistakable — one day ...-.- lands and your hand is already reaching to log the contact's end, no parsing happened at all. That is the whole craft of CW in miniature: grammar becoming reflex, so the conversation can carry the meaning.