SOS in Morse Code
SOS is the best known signal in the world: three dots, three dashes, three dots. Here is what it means, how to send it, and why it was chosen.
SOS in Morse Code
... --- ...
Three short signals, three long signals, three short signals — sent as one group.
What SOS Actually Means
SOS does not stand for anything. That surprises most people, but the letters were never an abbreviation. Radio delegates meeting in Berlin in 1906 needed a distress call that no operator could mistake for ordinary traffic, and they picked the sequence for how it sounds, not for what it spells.
Read as letters it happens to be S, O, S. Sent properly it is one unbroken run of nine signals with no letter gaps, which is why it is often written with a bar over the top. The phrases “Save Our Souls” and “Save Our Ship” came along later as memory aids.
What it replaced
Before 1906 the common distress call was CQD — the general call CQ plus D for distress. It had two problems: it was easy to confuse with a routine CQ, and it was harder to pick out through static.
SOS fixed both. The Titanic famously sent both signals in 1912, which is often miscast as the first use of SOS; by then it had already been the international standard for six years.
How to Send SOS
The rhythm is the whole message. Keep the long signals about three times the length of the short ones and leave a clear pause before repeating.
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With a light
Three quick flashes, three slow flashes, three quick flashes. Pause a few seconds, repeat.
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With sound
A whistle, a horn or banging on metal all work. Short–short–short, long–long–long, short–short–short.
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By tapping
Through a wall or pipe, the same pattern carries surprisingly far and is easy to recognise.
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Written down
Three of anything, three times over, is a recognised distress marker — including laid out on the ground.
If you have a phone, a radio or any way to call for help directly, use that first. SOS is what you fall back on when you can signal but cannot speak.
SOS Letter by Letter
Taken apart, SOS uses two of the easiest characters in the code:
- S —
...— three short signals - O —
---— three long signals
Sent as three separate letters there would be a three-unit gap between each one. As a
distress signal those gaps are dropped and the nine signals run together, which is what
makes it stand out from ordinary text. You can hear the difference by playing
... --- ... above and then typing “SOS” into the
Morse code translator, which spaces it as normal letters.
Both characters are in the Morse code alphabet, and the full reference including numbers and punctuation is on the Morse code chart.
Frequently Asked Questions
What is SOS in Morse code?
SOS is ... --- ... — three dots, three dashes, three dots, sent as one continuous sequence with no gaps between the letters.
What does SOS stand for?
Nothing. It is not an abbreviation. The sequence was chosen in 1906 purely because it is short, symmetrical and impossible to confuse with anything else. “Save Our Souls” and “Save Our Ship” were invented afterwards as memory aids.
How do you send SOS in Morse code?
Send three short signals, three long ones, then three short again, keeping the whole thing as a single group. A long signal lasts about three times as long as a short one. It works with a torch, a whistle, a mirror, a car horn or by tapping on a pipe.
Why was SOS chosen as the distress signal?
Because it is unmistakable. Nine signals in a strict pattern cut through noise and fading, and the sequence is symmetrical, so it reads the same even if someone only catches the middle of it. It replaced the earlier CQD signal at an international conference in 1906.
Is SOS still used today?
Not for official maritime distress traffic — that moved to the Global Maritime Distress and Safety System in 1999. It is still widely understood and still used informally: signalling with a light, tapping through a wall, or laying out three-three-three in the snow.
What is the difference between SOS and Mayday?
SOS is sent as a signal, in Morse; Mayday is spoken over the radio. They mean the same thing — a life-threatening emergency needing immediate help. Mayday came later, in the 1920s, once voice radio became practical.
How do you write SOS so it is not read as three letters?
In print it is normally written with a bar over it to show that it is one continuous sequence rather than S, O and S sent separately. Written out as dots and dashes it is ...---... without the usual letter gaps.
Can I send SOS with a flashlight?
Yes, and it is one of the most practical uses. Three quick flashes, three long flashes, three quick flashes, then pause for a few seconds and repeat. Keeping the rhythm regular matters more than the exact timing.