SOS in Morse Code
SOS is ... --- ..., three short, three long, three short.
It is worth knowing that this is one signal, not three letters. The nine elements run together with no letter gaps between them, and that is the reason it is printed with a line over the top: S̅O̅S̅. Sent with gaps it still reads as S, O, S and anyone will understand you, but the unbroken version is the convention, and it is the one that cannot be confused with a word that happens to start with those letters.
Characters stay fast while the gaps stretch, so each letter arrives as one rhythm and there is nothing to count.
How to send it
- Send three short flashes or tones, dot, dot, dot.
- Send three long ones, each about three times the length of a dot, dash, dash, dash.
- Send three short ones again, then pause and repeat the whole signal.
The ratio is what carries the meaning, not the speed. A dash is three dots long, the gap inside a letter is one dot, and the gap between repetitions is about seven. Send it slowly and evenly and it reads perfectly; send it fast and uneven and it does not.
Why these nine elements
The German government put ... --- ... into its radio regulations in 1905, and the second International Radiotelegraph Convention adopted it worldwide in 1906. It replaced a scatter of competing calls: the Marconi company used CQD, the US Navy used NC. The argument for it was purely practical: nine even elements in a memorable rhythm, hard to mistake for anything else, and simple enough to send by hand while a ship is going down.
Before SOS: CQD
The Marconi company's operators used CQD from 1904: CQ, the general call to all stations, with D for distress added. It worked, but it was a company convention, and other services had their own. The German regulations of 1905 introduced the nine-element signal, and the 1906 Berlin convention made it international from 1908. For a few years both were in use, and the most famous distress call in history used both: the Titanic's operators sent CQD first and then SOS, in April 1912, and were heard on both.
How it ended, and where it survives
Morse distress watch at sea ended formally in 1999, when the Global Maritime Distress and Safety System replaced it with satellite and digital calling. No ship is required to listen for SOS in Morse today. It survives where equipment does not: a torch, a whistle, a mirror, a hand on a pipe. Three short, three long, three short needs nothing but a way to make a signal long or short, and it is still the one pattern most people on Earth will recognise without any training at all.
Sending it without a key
With a torch, count in your head. One-and for a short flash, one-and-two-and-three-and for a long one, a short pause inside the group and a longer one before repeating. Evenness matters more than speed: a slow, regular SOS reads perfectly, a fast uneven one does not. With a whistle the same. And if you cannot remember the pattern at all, three of anything, evenly spaced and repeated, is the universal distress convention and needs no code.
Frequently asked
Does SOS stand for anything?
No. It was chosen in 1906 because ... --- ... is unmistakable and easy to send, not because of the letters. "Save Our Souls" and "Save Our Ship" were invented afterwards to help people remember it.
Why is it written SOS and not S O S?
Because it is not three letters. It is one continuous nine-element signal with no gaps between the groups, and references write it with an overbar to say so. Sent as three separate letters it is still understood, but the unbroken form is what the convention specifies.
Is SOS still used?
Not officially at sea. Morse distress calling ended in 1999 when GMDSS replaced it. It survives where equipment does not: a torch, a mirror, a whistle, or anything else that can make a long and a short signal.