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"CQD": The First International Distress Signal

#29 Science in History

01 February 1904

Today in 1904, “CQD” became the first international radio distress signal.

The history of maritime communication and distress signals dates to the early 19th century, when ships communicated with each other using flags, bells, and rockets. However, these signals were often ambiguous, and it was difficult for ships in distress to communicate their specific needs for help.

The “CQD” code was introduced by Marconi's wireless company. “CQ” had been in use as a call to “All Stations” or “Seeking You” but “D” was added to emphasise that it stood for a distress call – “All Stations, Distress” (possibly "Come Quickly, Danger". In 1905, the International Morse Code was introduced, which allowed ships to transmit messages using short and long tones which led, eventually, to the adoption of “SOS”

The change from "CQD" to "SOS" was made because the letters "SOS" were easy to recognize and remember, and they could be transmitted quickly and easily by Morse code. The three letters "SOS" were chosen because they are simple and easy to transmit, and they do not have any meaning in any language, making it an internationally recognized distress call.

The use of "SOS" as a distress call was first officially recognized in Berlin in 1906. Since then, it has become the standard distress call for ships and aircraft, and it is recognized by rescue services all over the world.

“CQD” wasn’t dropped immediately however – wireless operators still used it over the following years. Harold Bride and Jack Phillips, the wireless operators on the "Titanic," used both SOS and CQD distress signals on the night, in 1912, the ship fatally hit an iceberg.


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