Morse code is a method of transmitting text information as a series of on-off audible tones or light pulse. There are two different signal durations called dots and dashes (or dits and dahs). The International Morse Code standardize each number and letters of the alphabet with a unique sequence of dots and dashes.
Morse code was used in the 1890s as a form of radio communication before it was possible to transmit voice. It eventually became a primary means of communication during World War II by various countries for sending messages about enemies activities. Today, most militaries have stopped using Morse code. However, it is still commonly used in aviation as a way to identify navigational stations and among amateur radio operators to identify radio repeaters.