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| RTTY | |
|---|---|
| Name | Radioteletype |
| Invented | 1920s |
| Developers | A. H. Taylor, W. B. Arnold, E. F. W. Alexanderson |
| Medium | Shortwave, HF, VHF |
| Encoding | Baudot code, ITA2 |
| Modulation | FSK |
| Applications | Maritime, Aviation, Military, Amateur radio, News agencies |
RTTY RTTY is a radioteletype method for transmitting teletypewriter-style text over radio channels using frequency-shift keying and coded character sets. Originating in early 20th-century telegraphy experiments, it became integral to maritime and military communications and later to amateur radio, newswire services, and disaster response operations. Implementations intersect with developments at institutions such as Bell Labs, Marconi Company, RCA, ITT Corporation, and agencies like United States Navy and Royal Navy.
Early work on teleprinter transmission involved inventors and organizations including Émile Baudot, Emile Berliner, Guglielmo Marconi, Lee De Forest, and Rudolf Kompfner. Experiments in the 1920s and 1930s at Bell Labs, RCA and the British Post Office led to practical systems used by lines such as Western Union, Reuters, and the Associated Press. During World War II, Signals Intelligence efforts by units such as Bletchley Park, Ogden, and Central Bureau exploited radioteletype traffic alongside work by figures like Alan Turing, Bombe operators, and Gordon Welchman. Cold War era deployments included the United States Air Force, Soviet Navy, Royal Australian Navy, and systems developed by Siemens, ITT, and Philips. Post-war standardization involved organizations such as International Telecommunication Union, CCITT, and companies including Western Electric and Siemens-Schuckert.
RTTY uses discrete frequency signaling based on teleprinter signaling schemes like the Baudot code (ITA2), involving five-bit character sets and start/stop framing developed in telegraphy laboratories including Western Electric research groups. The method maps teleprinter contacts by shifting carrier frequencies, an approach studied at Massachusetts Institute of Technology and implemented by manufacturers such as Teletype Corporation and TAMCO. Key scientific contributions from researchers at Harvard University, Stanford University, and University of Cambridge informed error control and synchronization methods employed in operational networks like those run by Marconi International and Cable & Wireless.
RTTY typically employs frequency-shift keying (FSK) with mark and space tones, similar in principle to modulation techniques used in Frequency modulation experiments at Bell Labs and developments by Edwin Armstrong. Modes include standard FSK, single-sideband FSK as adopted by Amateur Radio operators associated with clubs such as the ARRL, and radio-teletype variations implemented by equipment vendors like Yaesu, Icom, Kenwood, and Heathkit. Military and maritime variants paralleled modulation research at Naval Research Laboratory and Defense Advanced Research Projects Agency facilities. Related transmission modes influenced by teleprinter multiplexing were used by services such as Aviation Radiotelegraphy and NTDS projects of the US Navy.
Operational RTTY systems historically combined teleprinters from Teletype Corporation, mechanical machines like the Model 15, and electromechanical interfaces developed by firms such as ITT and Western Electric. Radio equipment from RCA, Collins Radio, Harris Corporation, and Motorola provided transmitters and receivers adapted for FSK. Procedures used by operators trained at institutions including Royal Signals, RAF, and US Signal Corps specified tuning, carrier offset, and baud rates. In amateur setups, transceivers from Icom, Yaesu, and Kenwood are paired with interface units like those from Signalink or with soundcard modems developed at Amateur Radio Digital Communications. Field deployments for agencies such as Red Cross, United Nations peacekeeping, and Federal Emergency Management Agency used ruggedized equipment from Harris and Thales.
Standards development involved bodies such as the International Telecommunication Union (ITU), International Electrotechnical Commission, and CCITT (now ITU-T). Character encoding standards include ITA2 and later national adaptations referenced by organizations like ISO in character set studies and by ARINC for aeronautical communications. Operational protocol documents used by navies and airlines referenced guidance from ICAO and IMO. Technical specifications published by manufacturers like RCA, Collins, and Siemens defined frequency shifts, mark/space offsets, and baud rates used in public networks like Reuters wire services and private military networks operated by Northrop Grumman and Raytheon.
RTTY found primary application in maritime communications for ships operated by companies such as Cunard Line and Maersk, aviation message traffic for carriers like Pan American World Airways and British Airways, and news distribution services including Reuters, AP, and Agence France-Presse. Military use extended across branches including the United States Army, Royal Navy, Soviet Armed Forces, and French Armed Forces for tactical and strategic messaging. Amateur radio communities, represented by organizations like the American Radio Relay League and Radio Society of Great Britain, use RTTY for contesting, emergency communication, and historic reenactment. Humanitarian agencies including Médecins Sans Frontières and International Committee of the Red Cross have used RTTY-capable networks in logistics and disaster response.
RTTY offers robustness in narrowband shortwave channels and interoperability with legacy teleprinter equipment, but it is limited by low spectral efficiency compared with modern digital modes developed by DARPA and standards like TCP/IP-based telemetry and protocols from IETF. Error rates are influenced by propagation phenomena studied by researchers at National Oceanic and Atmospheric Administration and NASA and by ionospheric models from NOAA and ESA. Competing digital modes from amateur and professional sectors—such as PSK31, FT8, and PACTOR—developed by groups including SCS (Special Communications Systems), Joe Taylor (astronomer), and K1JT offer higher throughput and forward error correction. Regulatory oversight by Federal Communications Commission and national authorities constrains bandwidth and emission types for RTTY operation, affecting deployment in contested or congested spectrum environments.