Morse code is a system of communication that uses two different signal durations, called dots and dashes, to encode text characters. It was invented by Samuel F.B. Morse in the 1830s and became widely used for telegraphy, the transmission of messages over long distances by electric wires. Morse code can also be transmitted by other means, such as light, sound or radio waves. Morse code is still used today by amateur radio operators, pilots, sailors and some military forces.

"SOS" is an international distress signal, these three letters are not the abbreviation of any word, just because its code "...---..." (three dots, three long, three dots) is the easiest to send out and identify in telegrams code.