What Does SOS Mean?
SOS is the international distress signal in Morse code: three dots, three dashes and three dots. It means that a ship or a person is in serious danger and needs help at once.
SOS does not stand for "Save Our Souls" or "Save Our Ship". The letters were not chosen for their meaning. This guide explains what the signal is, how it is sent, where it came from and what replaced it.
What is SOS in Morse code?
SOS in Morse code is ... --- ... In the Morse alphabet, three dots are the letter S and three dashes are the letter O, which is how the signal got its name.
| Part | Morse code | As a letter |
|---|---|---|
| Three dots | ... | S |
| Three dashes | --- | O |
| Three dots | ... | S |
The patterns of all 26 letters are in the Morse code alphabet chart.
Does SOS stand for anything?
No. SOS is not an abbreviation. According to Wikipedia's article on SOS, it was simply a distinctive Morse code sequence and was at first not an abbreviation of anything.
| Claim | True? |
|---|---|
| SOS stands for "Save Our Souls" | No. The phrase was fitted to the letters later |
| SOS stands for "Save Our Ship" | No. The same |
| SOS was chosen because it is easy to send and hard to mistake | Yes |
A phrase that is invented afterwards to fit existing letters is called a backronym. "Save Our Souls" is the best known one.
How is SOS sent?
The real distress signal is sent as one unbroken pattern of nine signals, without the gaps that normally separate letters. Operators call such a signal a prosign and write it with a line over the letters.
The timing rules of International Morse code, set by the ITU, make the difference clear. A dash lasts three dots, the gap inside a letter one dot, and the gap between letters three dots.
| How it is sent | Pattern | Length |
|---|---|---|
| As the distress signal, without letter gaps | ...---... | 23 units |
| As the three letters S, O, S | ... --- ... | 27 units |
We calculated the two lengths from the ITU rules. The signal is repeated at short intervals, so a listener who misses the start still catches it.
Where did SOS come from?
The dates below are from Wikipedia's article on SOS.
| Date | Event |
|---|---|
| 1 February 1904 | The Marconi Company starts to use CQD as the distress call on its stations |
| 1 April 1905 | Germany adopts the SOS pattern as a distress signal in its national radio regulations |
| 3 November 1906 | The International Radiotelegraph Convention is signed and includes the signal for ships in distress |
| 1 July 1908 | The convention comes into effect |
| 10 June 1909 | The Cunard liner Slavonia uses SOS near the Azores, one of the first documented uses |
| 1912 | The radio operators of the Titanic send both CQD and SOS |
| 1927 | The spoken word "Mayday" is adopted as the voice equivalent |
| 1999 | The Global Maritime Distress and Safety System replaces SOS as the maritime standard |
After the Titanic, the older call CQD went out of use and SOS stayed. The wider story is in the guide on the history of Morse code.
How to signal SOS without a radio
The pattern works with anything that can be short or long: light, sound or movement. The rhythm is always three short, three long, three short.
| With | How |
|---|---|
| A torch or a phone light | Three short flashes, three long flashes, three short flashes, then a pause |
| A whistle or a horn | Three short blasts, three long blasts, three short blasts |
| Knocking | Three quick knocks, three slow knocks, three quick knocks |
| Writing | The letters SOS, large enough to be seen from far away |
Written SOS has a useful property that Wikipedia's article points out: the three letters read the same upside down.
In a real emergency, call the emergency number of your country first if you can. SOS by light or sound is for the case where no phone or radio works. Never send a distress signal as a joke; a false alarm sends rescuers to the wrong place.
SOS, Mayday and Pan-pan
| Signal | Sent by | Meaning |
|---|---|---|
| SOS | Morse code, light or sound | Distress: grave danger, help needed now |
| Mayday | Voice radio | The spoken equivalent of SOS |
| Pan-pan | Voice radio | Urgent, but no immediate danger to life |
"Mayday" comes from the French for "help me". It is the word for voice radio, where a spoken call replaces the Morse pattern.
How to write SOS in Morse code with a tool
Type SOS in our Morse code translator and it shows ... --- ... The tool writes the three letters with a space between them, as normal text is written in Morse code.
The translator shows Morse code as text only. It does not play sound or flash a light, so it is a tool for reading and writing the code, not for calling for help.
Frequently asked questions
- What does SOS stand for?
- Nothing. SOS is not an abbreviation. "Save Our Souls" and "Save Our Ship" were fitted to the letters after the signal was adopted.
- What is SOS in Morse code?
- Three dots, three dashes and three dots: ... --- ...
- When was SOS adopted?
- It was included in the International Radiotelegraph Convention signed on 3 November 1906, which came into effect on 1 July 1908, according to Wikipedia's article on SOS.
- Is SOS still used?
- At sea it was replaced as the standard in 1999 by the Global Maritime Distress and Safety System. The pattern is still widely known and is used as a visual or sound signal.
- What is the difference between SOS and Mayday?
- They mean the same. SOS is sent in Morse code, by light or by sound. Mayday is spoken on voice radio.