Morse Code
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.
Related Tools
Rail Fence Cipher
Rail Fence Cipher is a classical type of transposition cipher. It derives its name from the manner in which encryption is performed, in analogy to a fence built with horizontal rails.
Scytale Cipher
Scytale Cipher is a transposition cipher, which means it rearranges the order of letters in a message rather than substituting them with other characters.
Braille Cipher
Braille Cipher is a substitution cipher, it could encoding and substituting the letters in a message into "Braille" characters.