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Radioteletype (RTTY) is a telecommunications system consisting of two teleprinters linked by a radio link.
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.
Slow by modern standards
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.
Spectrum efficiency
Primary users
Principally users that need robust shortwave communications
- Various navies of the world
- Various armies of the world
- Diplomats, especially in Africa and parts of Asia
- RTTY systems are also fielded by amateur radio operators.
Pronunciation
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".
Spectrum usage
Media
See also
- Sailmail, a commercial HF mail system
- SITOR, an RTTY variant with error control.
- PACTOR, a packet SITOR variant
- Hellschreiber, a FAX-RTTY hybrid
- ACARS, used by commercial aviation – packet based
- Navtex, used by maritime navigation
- MT63, used by Hams and some government agencies
- PSK31 & PSK63
- MFSK
- COQUELET, also referred to generically as Polytone
- PICCOLO, also referred to generically as Polytone
- CLOVER2000
- Q15X25, a HAM created packet format
"Radioteletype"