International Morse encodes each character as a sequence of short and long signals — a dot (•, "dit") roughly 1 unit, a dash (—, "dah") roughly 3 units. Inter-element gap is 1 unit, inter-letter gap 3 units, and inter-word gap 7 units. The signal can be transmitted by radio key, by sound, or by light (Aldis lamp), making it the universal pre-digital backup for distress and identification.
Although GMDSS retired Morse as a mandatory distress watch in 1999, the alphabet remains in service for vessel-to-vessel light signalling, amateur and military radio, and as a fallback in degraded comms. The distress signal is three dots, three dashes, three dots — sent as one continuous group (…———…), not spelled as the letters S-O-S.
Audio generator
... --- ...
Try: SOS · MAYDAY · CQ DE · your callsign. Browser audio only — nothing is transmitted.
Alphabet
A.-
B-...
C-.-.
D-..
E.
F..-.
G--.
H....
I..
J.---
K-.-
L.-..
M--
N-.
O---
P.--.
Q--.-
R.-.
S...
T-
U..-
V...-
W.--
X-..-
Y-.--
Z--..
Numerals
0-----
1.----
2..---
3...--
4....-
5.....
6-....
7--...
8---..
9----.
Punctuation
..-.-.-Period (AAA)
,--..--Comma (MIM)
?..--..Question mark (IMI)
'.----.Apostrophe
!-.-.--Exclamation
/-..-.Slash / fraction bar
(-.--.Open parenthesis
)-.--.-Close parenthesis
&.-...Ampersand (AS — wait)
:---...Colon
;-.-.-.Semicolon
=-...-Equals (BT — break)
+.-.-.Plus (AR — end of message)
--....-Hyphen / dash
_..--.-Underscore
".-..-.Quotation
@.--.-.At sign
Prosigns
A prosign is two or more letters keyed without the inter-letter gap, treated as a single procedural symbol.
SOS...---...Distress — sent as one unbroken group, not three letters.
AR.-.-.End of message.
AS.-...Wait.
BT-...-Break / new paragraph.
CT / KA-.-.-Start of transmission / attention.
K-.-Invitation to transmit (over).
KN-.--.Invitation to a specific station only.
SK / VA...-.-End of contact / signing off.
HH........Error — disregard last word.
Common Q-codes & abbreviations
CQGeneral call to all stations.
CQ DEGeneral call from this station.
DEFrom (precedes own callsign).
QRTStop sending / I am closing down.
QRXStand by / wait.
QSLI acknowledge receipt.
QTHMy position is…
QRMInterference.
QRNAtmospheric noise (static).
QRZWho is calling me?
MAYDAYDistress (voice equivalent of SOS).
PAN-PANUrgency.
SECURITESafety / navigation warning.
73Best regards (sign-off).
88Love and kisses (informal sign-off).
Light signalling
For ship-to-ship Aldis lamp work the dot is a brief flash and the dash a held flash, with the same proportional timing. The receiving vessel acknowledges each word with a single "T" (—) and a complete message with "R" (•—•). Misread letters are corrected by sending eight dots ("HH") and resuming from the last good word.