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
Homophonic Substitution Cipher
Homophonic Substitution Cipher is a substitution cipher in which single plaintext letters can be replaced by any of several different ciphertext letters. They are generally much more difficult to break than standard substitution ciphers.
Playfair Cipher
Playfair Cipher is a manual symmetric encryption technique and was the first literal digram substitution cipher. It encrypts pairs of letters (bigrams or digrams), instead of single letters as in the simple substitution cipher and rather more complex Vigenère cipher systems then in use.
Polybius Square Cipher
Polybius Square Cipher is essentially identical to the simple substitution cipher, except that each plaintext character is enciphered as 2 ciphertext characters. It can ususally be detected if there are only 5 or 6 different characters in the ciphertext.
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.