SOS in Morse Code

Why SOS is one signal, not three letters

The distress signal was defined as a continuous sequence: three dots, three dashes, three dots. It happens to look like the letters S, O and S, which is how most people remember it, but operators send it without the gaps that would normally separate letters. In Morse terms it is a procedural signal (a prosign), written SOS with a line over the top.

Where SOS comes from

SOS became the international distress signal through the first International Radiotelegraph Convention, signed in Berlin on 3 November 1906 and in force from 1 July 1908. Its service regulations said that ships in distress shall use ··· −−− ···, repeated at brief intervals. Before that, the Marconi company used CQD, and as late as the sinking of the Titanic in April 1912 its operators sent both CQD and SOS.

Does SOS stand for “save our souls”?

No. When it was adopted, SOS was chosen as a distinctive sound, not as an abbreviation. Phrases such as “save our souls” and “save our ship” were attached to it later as memory aids.

Is SOS still used?

SOS remained the maritime radio distress signal until 1999, when ships moved to the Global Maritime Distress and Safety System (GMDSS). It is still recognised everywhere as a distress signal and can be sent any way you can: sound, a flashlight, a mirror, or tapping on a pipe or wall.

How to send SOS without a radio

• Flashlight or screen: three short flashes, three long flashes, three short flashes, then a pause, and repeat. Use Light or Torch above to send it for you.
• Sound or tapping: three quick taps, three slow taps, three quick taps. Keep the long ones about three times as long as the short ones.
• Written or on the ground: the letters S O S, as large as possible.