The former distress signal was CQD (Come Quikly Distress) which was very close to the signal CQ that was used for general calls. During the second International Radiotelegraphic Convention that occurred in Berlin on November 3, 1906, the signal “SOS”, which was already used by the German Marine, was thus adopted.

It was originally a continuous series of the famous sequence three dots – three dashes – three dots and the morse equivalent “SOS” was just used as a mnemonic. The use of sentences such as “Save ours souls” or “Save our ship” is posterior and they cannot be considered the origin of this signal.