CQD (transmitted in Morse code as ▄▄▄ ▄ ▄▄▄ ▄ ▄▄▄ ▄▄▄ ▄ ▄▄▄ ▄▄▄ ▄ ▄ ) is one of the first distress signals adopted for radio use. On 7 January 1904 the Marconi International Marine Communication Company issued "Circular 57", which specified that, for the company's installations, beginning 1 February 1904 "the call to be given by ships in distress or in any way requiring assistance shall be 'C Q D' ".[1]
- ^ Turnbull, G.E. (1913). "Distress Signalling". The Year-book of Wireless Telegraphy and Telephony. pp. 318–322. Archived from the original on 5 January 2021. Retrieved 21 August 2019.