I’d like to second TST’s recommendation of Neal McEwen’s ‘SOS,’ ‘CQD’ and the History of Maritime Distress Calls as a very good review of the history of distress calls.
Reviewing the Staff Report article:
In fact, SOS in not an acronym and it doesn’t represent anything at all.
It should also be stressed that, unlike CQD, the “SOS” distress signal really isn’t even three letters. From the beginning it has officially been …—… or three dots/three dashes/three dots all run together as a single entity. If you informally divide it into three equal parts it becomes “SOS” in Continental Morse code. However, in American Morse code, which was used by many U.S. ships through the first part of the twentieth century, — stood for the numeral “5”, so in this case the international distress signal was informally referred to as “S5S”. (See Francis A. Collins’ 1912 Some Stirring Wireless Rescues for more details.)
In 1908, an international committee tried to come up with a distress signal that would be easy to remember during a crisis, and could be transmitted by an amateur with only rudimentary knowledge of Morse Code. They decided a simple combination of threes: three letters, each represented by three marks, since three is a universally favored number. Well, at least in Western cultures.
The “SOS” distress signal actually dates back to at least April 1, 1905, when it was adopted by a national German law. (See Regelung der Funkentelegraphie im Deutschen Reich and German Regulations for the Control of Spark Telegraphy). It was next adopted as the international standard by the Berlin International Wireless Telegraph Convention, which was signed on November 3, 1906, and became effective on July 1, 1908. (See 1906 International Wireless Telegraph Convention/Service Regulation XVI.)
In Morse Code, the only letters represented by three identical marks are O (three dashes) and S (three dots). The committee toyed with OSO, but dashes are longer electrical signals to transmit than dots. An urgent message needed to be broadcast as quickly as possible and use as little power as possible, and so SOS became international standard.
I don’t know where this “committee” story comes from, but the simplest explanation is that the Convention merely adopted the distress signal that had already been in use in Germany for the past year-and-a-half. I’ve never seen any references to “OSO” being considered. And amateur operators certainly weren’t a factor, as they essentially didn’t exist in 1905/1906, and anyway, according to the 1906 Convention the distress signal was adopted for use by “ships in distress”.
During WWII, the signal “SSS” was adopted when the source of the emergency was a submarine attack, presumably so that potential rescue ships would know there was an enemy sub in the area.
Strings of S’s (three dashes each) had also been used during World War One to warn of submarines. From Bette Clemon’s Wake of the Wirelessman, a biography of her father as a shipboard radio operator during WWI: “Dale sat back and proceeded as usual to scan the dial listening for marine traffic. His heart jumped. He heard ‘.- -… .-… —.’ (ALLO) followed by a profusion of dashes in a triplet pattern, a warning as attention getting as SOS. He waited for the location. It came, ‘Cape Spartel.’ Dale phoned the bridge. ‘Submarine in our front yard, Cape Spartel.’”
DES–you are confusing the current, International Morse code which we now use with Morse’s original code scheme, the earlier mentioned “American Morse”. Morse’s original code had oddities such as inter-letter half-spaces, (O was dot/half space/dot) and a long-dash for L. The Morse code we now used is a European modification of Morse’s original code. The Original Morse Code Modified in Europe has a good review of the developments.