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SOS is communicated in Morse Code. Morse Code is a binary system of dots and dashes that can be communicated in a number of ways such as any device that can produce a contact, flash or bleep. A dot is one short contact, flash or bleep. A dash is one contact that's three times the signal length of a dot. Spoken words "dit" and "dah" are sometimes used to represent dots and dashes. SOS would look like this if spoken: Dit Dit Dit, dah dah dah, Dit Dit Dit. Play the SOS sound to hear an example of dots and dashes in action.
SOS is an internationally recognized Morse Code telegraph distress signal that is popularly known as "Save Our Souls" or "Save Our Ship" , but SOS is not actually an acronym for anything. The dot and dash order was chosen because it's easy to remember and execute. "Save Our Souls" or "Save Our Ship" were merely phases generated as an afterthought and probably meant as an easy way to remember this distress signal. The use of the SOS signal was first introduced in Germany as part of a set of national radio regulations in 1905. These regulations introduced three new Morse code sequences, including the internationally recognized SOS distress signal that replaced the CQD distress call.
Before the German Notzeichen SOS signal there was another distress signal referred to as CQD. "Come Quick, Danger", "Come Quickly Distress" are a couple of phrases commonly associated with CQD. However, just like the SOS catch phrases these sayings were merely afterthoughts. CQD means a general call to all vessels, which indicates the vessel sending is in distress and requires immediate assistance. CQD was never universally adopted and was phased out due to the possibility of mistaking it for other closely related Marconi codes used at the time.