SOS in Morse code
SOS is ... --- ... — three dots, three dashes, three dots. It is the best-known distress signal in the world, and you can send it with sound, with light, or even by knocking.
...---...
Sound plays at about 10 words per minute.
Tap it yourselfSend it as a secret message
How SOS is sent
In Morse code, S is three dots and O is three dashes. But SOS is not really sent as three separate letters. It is one signal, sent as a continuous pattern without the usual pause between letters: ...---.... Radio operators call a run-together signal like this a procedural sign, or prosign. The player above sends it the continuous way.
Say it as a rhythm: di-di-dit dah-dah-dah di-di-dit.
Does SOS stand for something?
No. "Save Our Souls" and "Save Our Ship" are popular explanations made up later. The pattern was chosen because it is easy to send, easy to recognize, and hard to mistake for anything else, even when the signal is weak.
A short history
SOS was adopted as the international distress signal at the International Radiotelegraph Convention in Berlin in 1906, and it took effect in 1908. Before that, operators of the British Marconi company used CQD. When the Titanic sank in 1912, its radio operators sent both CQD and SOS.
Ships stopped relying on Morse code for distress calls when the Global Maritime Distress and Safety System (GMDSS) took over in 1999. SOS is still understood everywhere as a call for help, sent with light, sound, or marks on the ground.
How to signal SOS with a flashlight or whistle
- Flashlight: three short flashes, three long flashes, three short flashes. Make the long flashes clearly longer — about three times the short ones.
- Whistle or horn: three short blasts, three long blasts, three short blasts.
- Knocking: three quick knocks, three slow knocks, three quick knocks.
- Then pause and repeat. Repeating the pattern is what tells people it is a real signal and not an accident.
In a real emergency, call your local emergency number first if you can. Signaling SOS is for when you can't.
Try it yourself
Open the tap pad and send SOS one letter at a time: tap briefly three times for S, hold three times for O, then tap three times again. The signal map lights up the path to each letter as you make it.
Tap it yourselfSend it as a secret message