SOS in Morse Code

SOS in Morse code is nine signals: three short, three long, three short — · · · − − − · · ·. Adopted internationally in 1906 and still the standard emergency signal today. No other code in history has saved more lives or been recognized by more people across more languages.

Below: the exact dot-dash pattern and its timing, what SOS actually stands for (not what you think), the history behind it, and five ways to signal it — flashlight, tapping, blinking, sound, and ground marks.

The SOS Morse Code Pattern

Three letters, but SOS is not sent as three separate letters. It's a prosign — a procedural signal transmitted as one continuous sequence with no gaps between the S, O, and S. In formal notation it's written with an overline: SOS. This distinction matters: standard Morse puts 3-unit pauses between letters, but SOS skips those pauses entirely. Every element flows directly into the next with only 1-unit intra-character gaps.

The pattern breaks down like this:

Nine signal elements. No inter-character gaps. At 20 words per minute, the entire sequence takes about 1.4 seconds. For the timing rules that underpin every Morse transmission, read How Morse Code Works.

What Does SOS Stand For?

Nothing. SOS is not an acronym. "Save Our Souls" and "Save Our Ship" are backronyms — phrases invented after the signal already existed to fit the letters.

The 1906 Berlin Radiotelegraphic Convention chose · · · − − − · · · for one reason: the pattern is unmistakable. Three dots, three dashes, three dots — symmetrical, rhythmic, and impossible to confuse with any other signal in the International Morse Code set. It's easy to send under stress, easy to recognize through static and noise, and easy to remember even if you know no other Morse.

Before SOS, different countries used different distress signals. British Marconi operators sent CQD ("All stations: distress"). Germany proposed SOE. Italy used SSSDDD. The convention needed a single universal signal that transcended language and operator training. The S-O-S letter combination was incidental — the pattern was the point.

For more on the encoding system behind these signals, see What Is Morse Code?

History of the SOS Distress Signal

The SOS signal has a specific, documented timeline:

• 1903 — Italy's Marconi Company adopts SSSDDD as its shipboard distress signal. Other nations use their own codes. No international standard exists.
• 1905 — Germany proposes · · · − − − · · · at a preliminary international radio conference. The pattern is noted for its simplicity.
• 1906 — The Berlin Radiotelegraphic Convention officially adopts the signal. Article XVI of the convention specifies it as the international distress sequence, effective July 1, 1908.
• 1909 — The SS Arapahoe sends what's generally recognized as the first SOS from an American ship, off Cape Hatteras.
• 1912 — The RMS Titanic sends both CQD and SOS during its sinking. Senior wireless operator Jack Phillips initially sent CQD; junior operator Harold Bride suggested the newer SOS signal. The disaster and subsequent press coverage make SOS universally known.
• 1999 — The Global Maritime Distress and Safety System (GMDSS) replaces Morse-based radio distress with satellite and digital systems. Maritime Morse watch ceases.
• Today — SOS remains the universal visual and audible distress signal. Apple's iPhone 14 and later models include satellite-based "Emergency SOS" features. Search-and-rescue teams still train for visual SOS signals. Broadcasting a false SOS is a federal offense under 47 U.S.C. § 325.

For the full story of Morse code's development from the 1830s telegraph to modern digital systems, see the History of Morse Code page (coming soon).

How to Signal SOS in Morse Code

The rhythm is always the same: short-short-short, long-long-long, short-short-short. The medium doesn't matter. Here are five methods, all field-tested in real emergencies:

• Flashlight — Three short flashes, three long flashes, three short flashes. Cover and uncover the lens to control timing. A "short" flash is about half a second; a "long" flash is roughly 1.5 seconds. Pause for 3 to 5 seconds after the full sequence, then repeat. Any flashlight works — a phone's camera flash, a headlamp, or a dedicated signal light. Aim toward potential rescuers, not straight up.
• Tapping — Three quick taps, three slow sustained taps, three quick taps. Knock against a wall, pipe, metal surface, or the floor. The key is the duration difference: short taps are sharp and quick, long taps are deliberate holds against the surface. Prisoners of war used wall-tapping to pass messages between cells — the "tap code" systems often included SOS as a priority signal.
• Blinking — Three fast blinks, three slow deliberate blinks, three fast blinks. Navy Commander Jeremiah Denton used Morse-coded blinks during a 1966 televised press conference as a POW in North Vietnam. While answering questions on camera, he blinked the word T-O-R-T-U-R-E in Morse code. Naval intelligence recognized the pattern from the broadcast footage. Blinking SOS uses the same technique with a simpler message.
• Sound — Three short blasts, three long blasts, three short blasts. Use a whistle, car horn, air horn, or your voice. The audible SOS pattern carries further than shouting "help" and is recognizable even when words aren't distinguishable. Many survival whistles are marketed with SOS instructions for this reason.
• Ground marks — Three short marks, three long marks, three short marks scratched in sand, snow, or dirt. Or arrange rocks, branches, or debris in the dot-dash pattern. Make it large enough to see from the air — rescue pilots look for geometric patterns that don't occur naturally.

Whichever method you use, the rhythm stays identical. Learn it once and you can signal it with anything that makes a mark, a sound, or a flash. Type "SOS" into the Morse Code Translator and play it back to hear the dot-dash timing firsthand.

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