RTTY (short for RadioTeleTYpe) is the first digital mode to be used by radio amateurs.
Teleprinter machines were first used for landline communication in the mid nineteenth century. Before that time, all telegraph communications had used Morse Code. This required a qualified Morse operator at each end of the circuit, and the data rate was slow because the speed was limited by the ability of the operators to copy Morse signals by ear.
(The Wireless Institute of Australia)
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