1904 – The distress signal “CQD” is established. But SOS became the common signal used.
CQD (transmitted in Morse code as _._. _ _._ _..) is one of the first distress signals adopted for radio use.
On 7th January 1904 the Marconi International Marine Communication Company issued “Circular 57”, which specified that, the call to be given by ships in distress or in any way requiring assistance shall be ‘C Q D’.
Source: 7th Day of January – Fatcowco