The International Morse Code, sometimes referred to as 'CW' in Amateur Radio jargon because a continuous wave is turned on and off with the long and short elements of the morse code characters, is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequence of short and long elements to represent the letters, numerals, punctuation and special characters of a given message. The short and long elements can be formed by sounds, marks, or pulses, in on off keying and are commonly known as "dots" and "dashes" or "dits" and "dahs". The speed of Morse code is measured in words per minute (WPM) or characters per minute, while fixed-length data forms of telecommunication transmission are usually measured in baud or bps.

Why is it called 'Morse Code'? This character encoding was devised by Samuel F. B. Morse, the creator of the electric telegraph. This 'Morse Code' came in two flavors, in the beginning. One was in use by the railroads of America, and is known as 'American Morse Code'. And, there was a unified, internationally-used version (adopted by radio operators), now known as the 'International Morse Code'. Now, when most people refer to 'Morse Code' or 'CW', they mean, 'International Morse Code.'

Currently, the most popular use of Morse code is by amateur radio operators, although it is no longer a requirement for amateur licensing in many countries. In the professional field, pilots and air traffic controllers are usually familiar with Morse code and require a basic understanding. Navigational aids in the field of aviation, such as VORs and NDBs, constantly transmit their identity in Morse code. Morse code is designed to be read by humans without a decoding device, making it useful for sending automated digital data in voice channels. For emergency signaling, Morse code can be sent by way of improvised sources that can be easily "keyed" on and off, making Morse code one of the most versatile methods of telecommunication in existence.