CQD (Morse Code _._. _ _ ._ _..) was a radio distress call that was commonly used by British ships in the early 20th century. It is a modification of the earlier CQ signal which meant "all stations." (preseumably D stands for distress) Many believe that CQD stands for for "Come Quick Distress", "Come Quick, Danger!" or "Come Quickly Dammit" etc. However, this is not true. While SOS had become the international standard in 1908, many British radio operators weren't enthusiastic to be adopting a distress signal that originated in Germany. Because of such, British ships often used this.
Harold Bride jokingly told Philips to also send SOS as "it may be our only chance to use it."Note: This appears in a deleted scene