“Send SOS,” one of the Titanic’s radio operators supposedly said to another after the famous ship struck that infamous iceberg. “It’s the new call and besides this may be your last chance to send it.”

That “new call” is 100 years old today, and people around the world who owe their lives to that piece of Morse code may reflect this morning on its importance.

In the past century, “SOS” has become a firm part of popular culture used in everything from DIY programme titles to Abba hits. But it began life in a far more serious setting after being adopted by the international community on July 1, 1908, as the globally recognised distress signal for ships at sea.

At that time voices could not yet be carried across the airwaves and sailors needed a standard means of saying, in Morse code, that they were in trouble.

Times Archive, 1912: The Titanic Inquiry

Mr Marconi explained the rules under which wireless operators in steamers work, especially as regards distress signals

Related Links

• SOS: not Save Our Souls, Sailors, Ships or Skins

• SOS, RIP

Until then, the most commonly used distress call was the “CQD” signal, which was open to misinterpretation. After much deliberation, SOS was chosen to replace it because the signal – three dots, three dashes and three more dots – is such a clear message to send in Morse code.

There was some early success for the new system a year later when the Cunard liner the SS Slavonia was stricken off the Azores. She sent out an SOS and not a single life was lost.

Even so, not everybody was convinced instantly, and it took the tragedy of the Titanic to reveal just how vital a universal system was. After the collision in April 1912, the ship’s radio operators sent out both the old CQD and the new SOS signals, but some ships in the area ignored both, thinking that they were having a party. They soon learnt otherwise, as international headlines told how Jack Phillips, the Titanic’s first radio operator, and 1,500 others had been lost along with the “unsinkable” ship. The new SOS distress signal was rarely ignored after that.

Of course, technology has moved on dramatically since 1908 and only very occasionally are the telltale dots and dashes that have saved countless lives employed today.

In the Times Archive: on July 2, 1909 wireless telegraphy saved the Cunard liner Slavonia

Times Recommends

• Secret files show Thatcher's role in coup plot
• Veterans to boycott Shell after ban on poppy sales
• 'I survived so please let Baby RB live too'