Radioteletype

Encyclopedia : R : RA : RAD : Radioteletype

Radioteletype (RTTY) is a telecommunications system consisting of two teleprinters linked by a radio link.

Contents

How it works

RTTY uses a variety of different modulation methods, of which frequency shift keying is the most common.

Coding used is typically 5-bit ITA2 code (also known as the Baudot code), which is used asynchronously with start and stop bits.
At least one common RTTY system uses 6-bit ITA2 character codes.
More modern systems use 7-bit or 8-bit bytes.

RTTY is extremely slow by modern standards; a typical baud rate for RTTY operation was 45 baud (approximately 60 words per minute).

The combination of low baud rate with robust FSK modulation makes RTTY highly resistant to most forms of radio interference, second only to Morse code.

RTTY and Packet spectrum efficiency compared with respect to thruput

Principally users that need robust shortwave communications

The pronunciation of RTTY is disputed

In very few applications, notably the U.S. military, radio teletype is known by the acronym RATT rather than RTTY.
Those who are actively engaged in amateur RTTY communications pronounce RTTY not by its initials but as "ritty".

Comparisons of MT63, RTTY and HF Packet spectrum