SOS full form is save our souls or save our ships. The worldwide Morse distress signal SOS was developed for use on the high seas. When written in formal notation, the letters “SOS” are separated by an overscore line to indicate that their Morse code equivalents are sent as a continuous sequence of three dots, three dashes, and three dots. To remember that in Universal Morse Code 3 dots form the character “S” and 3 dashes constitute the letter “O,” the mnemonic “S O S” was widely adopted.
Since its invention in the late 1890s (when it was still called “wireless telegraphy”), radio has been widely acknowledged as a vital tool for marine communication. Sailors used things like semaphore, signal flare, bells, & foghorns to communicate in the past, but now there are a few universally recognized visual and audible distress signals. However, at first, collaboration in standardizing radio distress signal was hampered by disparities in national approach and rivalry between competing radio corporations.
The Morse code sequence “TTT” (three “T’s” was adopted as the “Safety Signal”. The sequence is normally spaced as three letters to avoid confusion with the three dashes of the letter O.