Having these multiple distress signals was confusing and potentially dangerous. It meant that a ship in distress in foreign waters had a language barrier to overcome with would-be rescuers, even if using International Morse Code. Because of this and other issues, various countries decided to get together and discuss the idea of laying down some international regulations for radiotelegraph communications. In 1906, the International Wireless Telegraph Convention convened in Berlin, and delegates attempted to establish an international standard distress call. Marconi’s “-.-.–.–..”, and “………-..-..-..” (“SSSDDD”), which Italy had proposed at a previous conference, were deemed too cumbersome. Germany’s “…—…”, though, could be sent quickly and easily and was hard to misinterpret. It was chosen as the international distress signal for the nations who met at the conference, and went into effect on July 1, 1908.
Getting on Board with “SOS”
The first recorded use of “SOS” as a distress signal occurred just over a year later, in August 1909. The wireless operators on the SS Arapahoe sent the signal when the ship was disabled by a broken propeller off the coast of Cape Hatteras, North Carolina.
Not everyone got on board with the new standard as quickly, though. The Marconi Company was particularly reluctant to give up on “CQD.” The Marconi operators on board the Titanic initially just sent that signal after the ship struck an iceberg, until another operator suggested they try the new “SOS” signal, too.
A version of this story ran in 2012; it has been updated for 2023.
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