Morse Code (CW)
Not strictly classed as one of the digital modes, it’s included here because CW can be generated and decoded by computer software and CW is the oldest and simplest form of digital communication.
Morse code is named after Samuel F. B. Morse, inventor of the telegraph which used this system.
Morse is a very robust signalling system, it is possible for a skilled operator to decode the signal where most other communication modes would fail.
Letters and numbers are formed by dots and dashes created by turning an audio tone on and off in specific patterns. Download a copy of Morse code here – 120Kb PDF file.
Modern digital communication is simply sending data bits consisting of 1’s or 0’s, in other words, on or off as in CW.