SOS Accepted as Universal Distress Signal

Three Dots, Three Dashes, Three Dots

A man stranded on a beach next to an SOS sign made from rocks
Ragged businessman on beach with 'S.O.S.' made from rocks and shells. (Photo by Henrik Sorensen / Getty Images)

While "SOS" is an easily recognizable term now, there wasn't always an internationally recognized distress call. It was at a Radiotelegraphic Conference held in Berlin in 1906 that a need for one was recognized and chosen. However, it wasn't until two years later, July 1, 1908, that the International Morse Code signal "SOS" (three dots, three dashes, and then three dots) became the official distress call around the world.

Morse Code

For centuries, ships became isolated as soon as they left visual range of shore and of other ships. This meant that if a ship encountered any problems while at sea, they could sink without anyone knowing their fate. This isolation ended with the invention of the wireless telegraph and Morse Code.

Morse Code, invented in the 1830s in the United States by Samuel Morse, assigned a series of dashes and/or dots to each letter of the alphabet. These could then be transmitted over an electric telegraph and be deciphered on the other end.

As truly revolutionary as Morse Code was at the time, it was not able to be used internationally since it did not account for letters that had diacritic marks (such as acute, umlaut, or hacek). To correct this failing, a conference was held in Europe in 1851, which created the International Morse Code (sometimes called the Continental Morse Code).

Now that there was a universal code that all sailors could know and learn, it was time to create a universal distress call.

CQD - The First Distress Call

By 1904, many transatlantic ships had wireless telegraph capability on board. Realizing a need for a widely recognized distress call, the letters "CQD" became the first distress call. At the time, both on land and at sea, the letters "CQ" preceded any general message meant for all stations.

Thus "CQD" means "All stations, distress." (It was not "Come Quick Danger" as some will report.)

At the Radiotelegraphic Conference held in Berlin in 1906, it was noted that there needed to be an internationally agreed upon and recognized signal for distress. No longer should Great Britain use "CQD" while Germany used "SOE." A single distress call was needed.


After much discussion, the letters "SOS" were agreed upon. Although many have later stated that the letters stand for "Save Our Ship," "Save Our Souls," "Sink or Swim," or "Send Out Succor," this is not true. The letters were chosen for the ease and unmistakability of three dots, three dashes, and three dots and not for the actual letters of "SOS."

After being agreed upon at the 1906 conference, the Morse code signal of three dots, three dashes, and then three dots (sent together, without spacing) went into effect as the international signal for distress on July 1, 1908.

The Titanic

Although now officially the international signal for distress, many people still used the old signal of "CQD." Even in 1912, when the Titanic began to sink, its radio operator placed the "CQD" distress signal until another operator suggested to also send the new "SOS" signal.

It took several years for "SOS" to replace the old signal.


When radios began to replace the telegraph, a different term was needed for a distress call. It had to be a word that would be easily understandable over the radio but that was not used regularly in day-to-day speech.

The term "Mayday" (based on the French word "m'aidez," which means "help me") was selected in 1923 by senior London radio officer Frederick Stanley Mockford. Four years later, "Mayday" became the official voice distress call. To make sure it is clear, it is customary to say the word "Mayday" three times in a row when in distress.