How SOS is sent
SOS is a procedural signal, so it is sent without letter gaps: ...---... with only 1-unit gaps throughout. Written as three separate letters it would be ... --- ..., with 3-unit gaps after the S and the O. Listen to both versions above — the continuous form is the standard distress signal.
At 20 WPM the whole signal takes 1.38 seconds: 15 units of dots and dashes plus eight 1-unit gaps, 23 units of 60 ms each. When repeated, a word gap separates each SOS.
Where SOS came from
The signal was adopted at the International Radiotelegraph Convention signed in Berlin in 1906 and came into force in 1908. It was chosen because its rhythm is short, symmetrical and hard to mistake for anything else — not because the letters stand for words.
Using SOS as a light or sound signal
Because the pattern is so well known, SOS can be flashed with a torch or sounded with a whistle. The screen-flash tool above runs at a maximum of 6 WPM to stay below three flashes per second, and needs your confirmation before it starts.
Learn the rest of the code with the Morse alphabet, or type your own message into the translator.