What code was used in the navy before introducing SOS?

CQD
179
CDQ
131
DCQ
87
DSC
216
CQD is one of the first distress signals adopted for radio use. Although used worldwide by Marconi operators, CQD was never adopted as an international standard, since it could be mistaken for a general call "CQ" if the reception were poor. Germany's Notzeichen distress signal of three-dots/three-dashes/three-dots was adopted as the international Morse code distress signal. (This distress signal soon became known as "SOS" .
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