Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of GraphSearch.
Concept
CQD
Summary
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' ".
Land telegraphs had adopted the convention of using "CQ" ("sécu", from the French word sécurité) to identify alert, or precautionary messages of interest to all stations along a telegraph line. CQ had then been adopted in maritime radiotelegraphy as a "general call" to any ship or land station.
In landline use there was no general emergency signal, so the Marconi company added a "D" ("distress") to CQ in order to create a distress call. Sending "D" was already used internationally to indicate an urgent message. Thus, "CQD" was understood by wireless operators to mean All stations: Distress. Although used worldwide by Marconi operators, CQD was never adopted as an international standard, since it can easily be mistaken for a mere general call "CQ" when reception is poor.
At the first International Radiotelegraphic Convention, held in Berlin in 1906, 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" because it has the same dash-dot sequence as the letters S O S with the gaps between the letters removed, and in fact is properly written , with an overbar, to distinguish it from the three individual letters. In contrast, CQD is transmitted as three distinct letters with a short gap between each, like regular text. The SOS distress code is also easier to hear as it is nine symbols long, while no other character or sign is longer than six symbols. Germany had first adopted this distress signal in regulations effective 1 April 1905.
From 1899 to 1908, nine documented rescues were made by the use of wireless.
Official source
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.