Radioteletype often shortened to RTTY and pronounced "Ritty" or sometimes called Baudot or ITU-2 after the character encoding used (for reference ASCII is the standard for computers and is also used over radio but is very rare, ITU-2, which was originally called baudot and started off as a telegraph code is the standard for RTTY)

It transmits the 5-bit per character ITU-2 encoding via FSK, the exact baud rate and frequency shift depends on the kind of RTTY used, but the low baud rate and FSK modulation gives it a very distinctive "beedle-eedle" sound.

RTTY is what's known as a Keyboard-To-Keyboard mode, operating RTTY is sort of like text messaging albeit with some extra ettiquette for each side to understand when a message is finished and when they can start transmitting, some of the prosigns such as "SK" and "GA" are identical to those used in CW and also TDD (a form of AFSK RTTY over telephone lines used by deaf people before text messaging became common place).

Historically RTTY was sent and received via a teletype machine or terminal and a hardware modem, these days a computer with a soundcard/software modem is all what is needed.

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