KM4OLT - Mike's Ham Home
Transmitting and receiving text and data covers a wide range these days. From the radio teletype, to DMR, chat, messaging, and even email. To ensure reliability of transmission and reception there has been a host of different protocols to deal with things like error correction, etc.
Here are a few:
Amateur teleprinting over radio (AMTOR)
D-STAR (Digital Data) a high speed (128 kbit/s) - many have used it to replace analog modes in repeaters.
Hellschreiber, also referred to as Hell
Multi Tone 63 (MT63)
Multiple frequency-shift keying (MFSK) modes such as
Packet radio (AX.25)
Automatic Packet Reporting System (APRS) - Used for tracking the location of a transmitter. Some radios use it to automatically locate nearby repeaters instead of having to key every one in during your travels.
31 baud binary phase shift keying: PSK31
31 baud quadrature phase shift keying: QPSK31
63 baud binary phase shift keying: PSK63
63 baud quadrature phase shift keying: QPSK63