SOS, MAYDAY, distress calls: Morse code can save your life

Nine signals. Three seconds. That's all that separates someone who can send an SOS from someone waving their arms and hoping to be seen.

··· −−− ···

Three short, three long, three short. It's the one code everybody should know by heart — and the only one that still works with a torch, a whistle, a mirror, a saucepan, or a stone banged against a rock.

SOS doesn't stand for anything (and that's exactly why it works)

First myth to kill: SOS is not an acronym for "Save Our Souls", nor "Save Our Ship". Those phrases were invented after the fact.

The pattern was chosen at the Berlin radiotelegraph conference in 1906 (effective 1 July 1908) for a purely practical reason: it is the simplest pattern to send and the most recognisable in noise that anyone could design.

One detail almost nobody knows: SOS is sent in one continuous run, with no gaps between the letters. Not "S, then O, then S", but ···−−−···. That continuity is what makes it identifiable even to someone who doesn't know Morse.

SOS, MAYDAY, PAN-PAN: not synonyms

Three signals, three severity levels, three different channels. Confusing them costs time — and time is exactly the resource you're short of.

MAYDAY comes from the French "m'aider" (help me), proposed in 1923 by Frederick Mockford, a radio officer at Croydon, and adopted in 1927. PAN-PAN comes from "panne" (breakdown).

Simple rule of thumb: MAYDAY when lives are at stake, PAN-PAN when it's serious but not (yet) life-threatening. A dead engine offshore with no immediate risk is PAN-PAN. A hull breach taking on water is MAYDAY.

How to send an SOS with whatever you have

Morse timing is simple: a dash lasts three times a dot. In a real situation, count in seconds.

With a torch or a phone light

1. Three flashes of 1 second, 1 second apart. (S)
2. Three flashes of 3 seconds, 1 second apart. (O)
3. Three flashes of 1 second. (S)
4. Pause 7 seconds, then start again.

With a whistle — same rhythm: three short blasts, three long, three short. A whistle carries far further than a voice and barely tires you.

With a signal mirror — sun flashes are visible for kilometres, including from an aircraft: aim at the target and break the beam on the SOS rhythm.

On the ground, to be seen from the air — lay out a giant SOS with rocks, wood or brightly coloured clothing. Three fires in a triangle are the other universally recognised signal.

And one rule holds for every method: repeat. A rescuer needs to see or hear the pattern two or three times before identifying it as deliberate.

In the mountains, the signal is different

The international alpine distress signal is not the same:

• Call for help: 6 signals (sound or light) per minute, then 1 minute of silence, then repeat.
• Rescuer's reply: 3 signals per minute — "message received, we're coming".

SOS is understood everywhere, but in the Alps the 6/1 rhythm is the official code.

Three real cases where Morse changed the outcome

• 1966, Vietnam. US pilot Jeremiah Denton, a prisoner of war, is filmed for a propaganda interview. Facing the camera, he blinks in Morse: T-O-R-T-U-R-E. Naval intelligence decodes the footage — the first documented proof of the mistreatment of prisoners.
• 2020, Pacific. Three mariners stranded on Pikelot Island, Micronesia, trace a huge SOS in the sand using palm fronds. An aircrew spots it. All three are recovered.
• 1912, North Atlantic. The Titanic's operator alternates CQD and SOS for more than two hours. The Carpathia picks up the signal 93 km away and rescues 705 survivors. After that night, nobody used CQD again.

What you must never do

• Send an SOS as a test. A false call launches real rescue assets and is a punishable offence in most countries.
• Stop after one signal. Repeat every minute until you get a response.
• Save your battery so hard you send nothing. A signal sent beats a full torch found next to you.

The one code to remember today

··· −−− ··· — three short, three long, three short. Repeated every minute.

S and O are among the simplest letters in the Morse alphabet: they arrive as early as chapter 5 of the path. The full story of the signal is here.

FAQ

What does SOS mean in Morse code?

SOS doesn't stand for anything. Neither "Save Our Souls" nor "Save Our Ship" — those phrases were invented after the fact. The pattern ···−−−··· was chosen in 1906 because it is the simplest to send and the most recognisable in noise. The letters S, O, S are merely its written transcription.

What is the difference between SOS and MAYDAY?

SOS is the distress signal in Morse, MAYDAY its spoken equivalent, said three times. Both mean grave and imminent danger. PAN-PAN, also repeated three times, is one level below: a serious urgency with no immediate threat to life.

How do you send an SOS with a torch?

Three flashes of 1 second, three flashes of 3 seconds, three flashes of 1 second, with 1 second between each. Pause 7 seconds, then start again — at least every minute.

Go further

• Complete interactive Morse alphabet
• The letter S · The letter O
• The 5 techniques to memorise the Morse alphabet fast

▶ Learn SOS in 90 seconds — free, no email required. Share this article: one day, someone will remember it at the right moment.