SOS is the most important signal in Morse code — and possibly the most important signal you'll ever learn. Three short, three long, three short. It can be sent by sound, light, tapping, or radio, and is recognised worldwide without any language barrier.
This guide shows you exactly how to do it using five different methods.
SOS is sent as one continuous unit — no gaps between the letters:
Key rule: SOS is sent as one unbroken unit — ···−−−··· — with no extra gaps between S and O. This makes it instantly recognisable and impossible to confuse with any other signal.
Press and release quickly for dots — hold for 3× as long for dashes. Point at aircraft, ships, or any potential rescuer. Works day and night.
Tap on any hard surface — pipe, wall, floor, rock. Quick tap = dot, held tap = dash. Used by trapped survivors to signal through rubble or walls.
Three short blasts, three long blasts, three short blasts. Any sound-making device works — whistle, car horn, air horn, fog horn, or banging on metal.
Reflect sunlight at aircraft or ships. Cover and uncover the reflection — quick cover = dot, long cover = dash. Visible up to 16km in bright sunlight.
On VHF Channel 16 (marine) or 121.5 MHz (aviation) — key the transmitter in SOS pattern, or say "MAYDAY MAYDAY MAYDAY" followed by your position. Both are equally valid distress calls.
Always repeat SOS continuously — send it over and over with a pause between each transmission. A single SOS may be missed. Rescuers are listening for a pattern, not a single burst.
If you have time and materials, create a large SOS on the ground visible from aircraft:
Use our translator to hear SOS played at different speeds — train your ear so you recognise it instantly if you ever hear it.
Open Morse Code Translator