There is much mystery and misinformation surrounding the origin and use of maritime distress calls. Most of the general populace believes that "SOS" signifies "Save Our Ship." Casual students of radio history are aware that the use of "SOS" was preceded by "CQD." Why were these signals adopted? When were they used?
The practical use of wireless telegraphy was made possible by Guglielmo Marconi in the closing years of the 19th century. Until then, ships at sea out of visual range were very much isolated from shore and other ships. The wireless telegraphers used Morse Code to send messages. Morse Code is a way of "tapping" out letters using a series of dots (short signals) and dashes (long signals). Spoken, short signals are referred to as "dih" and long signals are referred to as "dah". The letter "A" is represented by a dot followed by a dash:
By 1904 there were many trans-Atlantic British ships equipped with wireless communications. The wireless operators came from the ranks of railroad and postal telegraphers. In England a general call on the landline wire was a "CQ." "CQ" preceded time signals and special notices. "CQ" was generally adopted by telegraph and cable stations all over the world. By using "CQ," each station receives a message from a single transmission and an economy of time and labor was realized. Naturally, "CQ," went with the operators to sea and was likewise used for a general call. This sign for "all stations" was adopted soon after wireless came into being by both ships and shore stations.
In 1904, the Marconi company suggested the use of "CQD" for a distress signal. Although generally accepted to mean, "Come Quick Danger," that is not the case. It is a general call, "CQ," followed by "D," meaning distress. A strict interpretation would be "All stations, Distress."
At the second Berlin Radiotelegraphic Conference 1906, the subject of a danger signal was again addressed. Considerable discussion ensued and finally SOS was adopted. The thinking was that three dots, three dashes and three dots could not be misinterpreted. It was to be sent together as one string.
The Marconi Yearbook of Wireless Telegraphy and Telephony , 1918 states, "This signal [SOS] was adopted simply on account of its easy radiation and its unmistakable character. There is no special signification in the letter themselves, and it is entirely incorrect to put full stops between them [the letters]." All the popular interpretations of "SOS," "Save Our Ship," "Save Our Souls," or "Send Out Succour" are simply not valid. Stations hearing this distress call were to immediately cease handling traffic until the emergency was over and were likewise bound to answer the distress signal.
Although the use of "SOS" was officially ratified in 1908, the use of "CQD" lingered for several more years, especially in British service where it originated. It is well documented in personal accounts of Harold Bride, second Radio Officer, and in the logs of the SS Carpathia, that the Titanic first used "CQD" to call for help. When Captain Smith gave the order to radio for help, first radio officer Jack Phillips sent "CQD" six times followed by the Titanic call letters, "MGY." Later, at Brides suggestion, Phillips interspersed his calls with "SOS." In SOS to the Rescue, 1935, author Baarslag notes, "Although adopted intentionally in 1908, it [SOS] had not completely displaced the older 'CQD' in the British operators' affections." (It is interesting to observe that Marconi was waiting in New York to return home to England on the Titanic.)
The first recorded American use of "SOS" was in August of 1909. Wireless operator T. D. Haubner of the SS Arapahoe radioed for help when his ship lost its screw near Diamond Shoals, sometimes called the "Graveyard of the Atlantic." The call was heard by the United Wireless station "HA" at Hatteras. A few months later, the SS Arapahoe received an "SOS" distress call from the SS Iroquois. Radio Officer Haubner therefore has the distinction of being involved in the first two incidents of the use of "SOS" in America, the first as the sender and the second as the receiver. The U.S. did not officially adopt "SOS" until 1912, being slow to adopt international wireless standards.
SOS Accepted as Universal Distress Signal (1908): For centuries, ships became isolated as soon as they left visual range of shore and of other ships. This meant that if a ship encountered any problems while at sea, they could sink without anyone knowing their fate. This isolation ended with the invention of the wireless telegraph and Morse Code.
By 1904, many transatlantic ships had wireless telegraph capability on board. Realizing a need for a widely recognized distress call, the letters "CQD" became the first distress call. At the time, both on land and at sea, the letters "CQ" preceded any general message meant for all stations. Thus "CQD" means "All stations, distress" and not "Come Quick Danger."
At the Radiotelegraphic Conference held in Berlin in 1906, it was noted that there needed to be an internationally agreed upon and recognized signal for distress. No longer should Great Britain use "CQD" while Germany used "SOE." A single distress call was needed.
After much discussion, the letters "SOS" was agreed upon. Although many have later stated that the letters stand for "Save Our Ship," "Save Our Souls," "Sink or Swim," or "Send Out Succor," this is not true. The letters were chosen for the ease and unmistakability of three dots, three dashes, and three dots and not for the actual letters of "SOS."
After being agreed upon at the 1906 conference, the Morse code signal of three dots, three dashes, and then three dots (sent together, without spacing) went into effect as the international signal for distress on July 1, 1908.
Although now officially the international signal for distress, many people still used the old signal of "CQD." Even in 1912, when the Titanic began to sink, its radio operator placed the "CQD" distress signal until another operator suggested to also send the new "SOS" signal. It took several years for "SOS" to replace the old signal.