What does the distress signals CQD and SOS stand for in Morse code?

Answer 1

Why?

Morse Code can be laborious to send and slow when using a hand pump style of key. Therefore various code systems were used by operators to shorten the time it took to send messages. In the early days of Morse code on ships there was a book published which has these codes in it. of those short version codes CQ, 73's 88's and a few other number codes are the only one remaining.

In the case of CQ it was simply a invitation for any wireless operator who could receive the call to answer. There were varients of this CQ followed by the callsign such as "CQ CQ CQ G4ZQM DE G0TMH " was a specific request for a station to reply ( In the example radio station G0TMH is calling G4ZQM the DE means 'from'). CQDX requests a long distance communication. (All of these codes are used by radio hams today using Morse).

CQD was the internationally recognised call requesting any station to respond to a distress call (One assumes the D of CQD stands for "distress").

Other codes and cyphers existed such as the number codes 73's and 88's which were used by radio operators to shorten messages for passengers on ships who regularly said the same thing such as "Best wishes" (73) and "Love and kisses" (88). Most of these number codes have been lost in time and there is no copies of the radio offices code books available. It is also likely that each shipping company had its own short version codes to encrypt traffic from other companies and ships listening in.

SOS

The letters of S O S in Morse code are the sounds ... --- ... (short short short, long long long, short short short);

These are the extremes of opposite in Morse code. Consider that 911 in USA is used on the key pad for a phone because it is at the extreme ends of the keypad and therefore unlikely to be pressed by accident. The same logic occurs in Morse.

Later on the letters S O S were attributed to the phrase Save Our Souls but in fact had nothing to do with the reason SOS was chosen.