CQD, transmitted in Morse code as – · – · – – · – – · · is one of the first distress signals adopted for radio use. It was announced on Jan. 7, 1904, by "Circular 57" of the , and became effective, beginning Feb. 1, 1904 for Marconi installations.
Land telegraphs had traditionally used "CQ" ("sécu," from the French word sécurité) to identify alert or precautionary messages of interest to all stations along a telegraph line, and CQ had also been adopted as a "general call" for maritime radio use.
However, in landline usage there was no general emergency signal, so in 1904 the Marconi International Marine Communication Company added a "D" ("distress") to CQ in order to create its distress call. Thus, "CQD" is understood by wireless operators to mean, "All stations: distress."
Contrary to popular belief, CQD does not stand for "Come Quick, Danger", "Come Quickly: Distress", or "Come Quick — Drowning!"
SOS was first adopted by the German government in radio regulations effective April 1, 1905, and became the worldwide standard on July 1, 1908.
On April 14-15, 1912, RMS Titanic radio operator Jack Phillips initially sent "CQD," which was still commonly used by British ships. Harold Bride, the junior radio operator, reminded Phillips that the new code was SOS and allegedly said, "Send SOS, it's the new call, and it may be your last chance to send it." The two codes were alternated until they abandoned the ship. (Phillips died before rescue, but Bride survived.)
Incidentally, SOS, the international Morse code distress signal (· · · – – – · · ·), is thought to stand for "save our ship," "save our souls," or "send out succour," but SOS does not actually stand for anything.
SOS remained the maritime radio distress signal until 1999, when it was replaced by the Global Maritime Distress Safety System. SOS is still recognized as a visual distress signal.
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