Teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an
Initially, from 1887 at the earliest, teleprinters were used in
With the development of early
Teleprinters have largely been replaced by fully electronic computer terminals which typically have a computer monitor instead of a printer (though the term "TTY" is still occasionally used to refer to them, such as in Unix systems). Teleprinters are still widely used in the aviation industry (see AFTN and airline teletype system),[4] and variants called Telecommunications Devices for the Deaf (TDDs) are used by the hearing impaired for typed communications over ordinary telephone lines.
History
This section may be in need of reorganization to comply with Wikipedia's layout guidelines. The reason given is: it could be more easily read if subdivided by principle of operation. (March 2024) |
The teleprinter evolved through a series of inventions by a number of engineers, including
There were a number of parallel developments on both sides of the Atlantic Ocean. In 1835 Samuel Morse devised a recording telegraph, and Morse code was born.[6] Morse's instrument used a current to displace the armature of an electromagnet, which moved a marker, therefore recording the breaks in the current. Cooke & Wheatstone received a British patent covering telegraphy in 1837 and a second one in 1840 which described a type-printing telegraph with steel type fixed at the tips of petals of a rotating brass daisy-wheel, struck by an "electric hammer" to print Roman letters through carbon paper onto a moving paper tape.[7] In 1841 Alexander Bain devised an electromagnetic printing telegraph machine. It used pulses of electricity created by rotating a dial over contact points to release and stop a type-wheel turned by weight-driven clockwork; a second clockwork mechanism rotated a drum covered with a sheet of paper and moved it slowly upwards so that the type-wheel printed its signals in a spiral. The critical issue was to have the sending and receiving elements working synchronously. Bain attempted to achieve this using centrifugal governors to closely regulate the speed of the clockwork. It was patented, along with other devices, on April 21, 1841.[8]
By 1846, the
Landline teleprinter operations began in 1849, when a circuit was put in service between Philadelphia and New York City.[9]
In 1855, David Edward Hughes introduced an improved machine built on the work of Royal Earl House. In less than two years, a number of small telegraph companies, including Western Union in early stages of development, united to form one large corporation – Western Union Telegraph Co. – to carry on the business of telegraphy on the Hughes system.[10]
In France, Émile Baudot designed in 1874 a system using a five-unit code, which began to be used extensively in that country from 1877. The British Post Office adopted the Baudot system for use on a simplex circuit between London and Paris in 1897, and subsequently made considerable use of duplex Baudot systems on their Inland Telegraph Services.[11]
During 1901, Baudot's code was modified by
In the United States in 1902, electrical engineer Frank Pearne approached
In 1908, a working teleprinter was produced by the Morkrum Company (formed between Joy Morton and Charles Krum), called the Morkrum Printing Telegraph, which was field tested with the Alton Railroad. In 1910, the Morkrum Company designed and installed the first commercial teletypewriter system on Postal Telegraph Company lines between Boston and New York City using the "Blue Code Version" of the Morkrum Printing Telegraph.[16][17]
In 1916,
Instead of wasting time and money in patent disputes on the start-stop method, Kleinschmidt and the Morkrum Company decided to merge and form the
In 1924 Britain's Creed & Company, founded by Frederick G. Creed, entered the teleprinter field with their Model 1P, a page printer, which was soon superseded by the improved Model 2P. In 1925 Creed acquired the patents for Donald Murray's Murray code, a rationalised Baudot code. The Model 3 tape printer, Creed’s first combined start-stop machine, was introduced in 1927 for the Post Office telegram service. This machine printed received messages directly on to gummed paper tape at a rate of 65 words per minute. Creed created his first keyboard perforator, which used compressed air to punch the holes. He also created a reperforator (receiving perforator) and a printer. The reperforator punched incoming Morse signals on to paper tape and the printer decoded this tape to produce alphanumeric characters on plain paper. This was the origin of the Creed High Speed Automatic Printing System, which could run at an unprecedented 200 words per minute. His system was adopted by the Daily Mail for daily transmission of the newspaper's contents. The Creed Model 7 page printing teleprinter was introduced in 1931 and was used for the inland Telex service. It worked at a speed of 50 baud, about 66 words a minute, using a code based on the Murray code.[citation needed]
A teleprinter system was installed in the
Ways in which teleprinters were used
Teleprinters could use a variety of different communication channels. These included a simple pair of wires, public switched telephone networks, dedicated non-switched telephone circuits (leased lines), switched networks that operated similarly to the public telephone network (telex), and radio and microwave links (telex-on-radio, or TOR).
There were at least five major types of teleprinter networks:
- Exchange systems such as area codes were reserved for teleprinter use. German systems did "dialing" via the keyboard. Typed "chat" was possible, but because billing was by connect time, it was common to prepare messages in advance on paper tapeand transmit them without pauses for typing.
- Leased line and radioteletype networks arranged in point-to-point and / or multipoint configurations supported data processing applications for government and industry, such as integrating the accounting, billing, management, production, purchasing, sales, shipping and receiving departments within an organization to speed internal communications.
- Autodin.
- Broadcast systems such as weather information distribution and "news wires", which were received on "wire machines".UPI). Information was printed on receive-only teleprinters, without keyboards or dials.
- "Loop" systems, where anything typed on any machine on the loop printed on all the machines. American police departments used such systems to interconnect precincts.[25]
Before the
Teleprinter operation
Most teleprinters used the 5-
When the line is broken, the continuous spacing (open circuit, no current flowing) causes a receiving teleprinter to cycle continuously, even in the absence of stop bits. It prints nothing because the characters received are all zeros, the ITA2 blank (or ASCII) null character.
Teleprinter circuits were generally leased from a communications
Earlier teleprinters had three rows of keys and only supported upper case letters. They used the 5 bit ITA2 code and generally worked at 60 to 100 words per minute. Later teleprinters, specifically the Teletype Model 33, used ASCII code, an innovation that came into widespread use in the 1960s as computers became more widely available.
"Speed", intended to be roughly comparable to words per minute, is the standard term introduced by Western Union for a mechanical teleprinter data transmission rate using the 5-bit ITA2 code that was popular in the 1940s and for several decades thereafter. Such a machine would send 1 start bit, 5 data bits, and 1.42 stop bits. This unusual stop bit time is actually a rest period to allow the mechanical printing mechanism to synchronize in the event that a garbled signal is received.[26] This is true especially on high frequency radio circuits where selective fading is present. Selective fading causes the mark signal amplitude to be randomly different from the space signal amplitude. Selective fading, or Rayleigh fading can cause two carriers to randomly and independently fade to different depths.[27] Since modern computer equipment cannot easily generate 1.42 bits for the stop period, common practice is to either approximate this with 1.5 bits, or to send 2.0 bits while accepting 1.0 bits receiving.
For example, a "60 speed" machine is geared at 45.5 baud (22.0 ms per bit), a "66 speed" machine is geared at 50.0 baud (20.0 ms per bit), a "75 speed" machine is geared at 56.9 baud (17.5 ms per bit), a "100 speed" machine is geared at 74.2 baud (13.5 ms per bit), and a "133 speed" machine is geared at 100.0 baud (10.0 ms per bit). 60 speed became the de facto standard for amateur radio RTTY operation because of the widespread availability of equipment at that speed and the U.S. Federal Communications Commission (FCC) restrictions to only 60 speed from 1953 to 1972. Telex, news agency wires and similar services commonly used 66 speed services. There was some migration to 75 and 100 speed as more reliable devices were introduced. However, the limitations of HF transmission such as excessive error rates due to multipath distortion and the nature of ionospheric propagation kept many users at 60 and 66 speed. Most audio recordings in existence today are of teleprinters operating at 60 words per minute, and mostly of the Teletype Model 15.
Another measure of the speed of a teletypewriter was in total "operations per minute (OPM)". For example, 60 speed was usually 368 OPM, 66 speed was 404 OPM, 75 speed was 460 OPM, and 100 speed was 600 OPM. Western Union Telexes were usually set at 390 OPM, with 7.0 total bits instead of the customary 7.42 bits.
Both wire-service and private teleprinters had bells to signal important incoming messages and could ring 24/7 while the power was turned on. For example, ringing 4 bells on UPI wire-service machines meant an "Urgent" message; 5 bells was a "Bulletin"; and 10 bells was a FLASH, used only for very important news.
The teleprinter circuit was often linked to a 5-bit
Communication by radio, known as radioteletype or RTTY (pronounced ritty), was also common, especially among military users. Ships, command posts (mobile, stationary, and even airborne) and logistics units took advantage of the ability of operators to send reliable and accurate information with a minimum of training. Amateur radio operators continue to use this mode of communication today, though most use computer-interface sound generators, rather than legacy hardware teleprinter equipment. Numerous modes are in use within the "ham radio" community, from the original ITA2 format to more modern, faster modes, which include error-checking of characters.
Control characters
A typewriter or electromechanical printer can print characters on paper, and execute operations such as move the carriage back to the left margin of the same line (
Answer back mechanism
Some teleprinters had a "Here is" key, which transmitted a fixed sequence of 20 or 22 characters, programmable by breaking tabs off a drum. This sequence could also be transmitted automatically upon receipt of an ENQ (control E) signal, if enabled.[28][29] This was commonly used to identify a station; the operator could press the key to send the station identifier to the other end, or the remote station could trigger its transmission by sending the ENQ character, essentially asking "who are you?"
Manufacturers
Creed & Company
British Creed & Company built teleprinters for the GPO's teleprinter service.[30]
- Creed model 7 (page printing teleprinter introduced in 1931)
- Creed model 7B (50 baud page printing teleprinter)
- Creed model 7E (page printing teleprinter with overlap cam and range finder)
- Creed model 7/TR (non-printing teleprinter reperforator)
- Creed model 54 (page printing teleprinter introduced in 1954)
- Creed model 75 (page printing teleprinter introduced in 1958)
- Creed model 85 (printing reperforator introduced in 1948)
- Creed model 86 (printing reperforator using 7/8" wide tape)
- Creed model 444 (page printing teleprinter introduced in 1966, GPO type 15)
Gretag
The Gretag ETK-47 teleprinter developed in Switzerland by
Kleinschmidt Labs
In 1931, American inventor Edward Kleinschmidt formed
Kleinschmidt machines, with the military as their primary customer, used standard military designations for their machines. The teleprinter was identified with designations such as a TT-4/FG, while communication "sets" to which a teleprinter might be a part generally used the standard Army/Navy designation system such as AN/FGC-25. This includes Kleinschmidt teleprinter TT-117/FG and tape reperforator TT-179/FG.
Morkrum
Olivetti
Italian office equipment maker Olivetti (est. 1908) started to manufacture teleprinters in order to provide Italian post offices with modern equipment to send and receive telegrams. The first models typed on a paper ribbon, which was then cut and glued into telegram forms.
- Olivetti T1 (1938–1948)
- Olivetti T2 (1948–1968)
- Olivetti Te300 (1968–1975)
- Olivetti Te400 (1975–1991)
Siemens & Halske
- Teleprinter Model 100 Ser 1 (end of the 1950s) – Used for Telex service[37]
- Teleprinter Model 100 Ser. 11 – Later version with minor changes
- Teleprinter Model T100 ND (single current) NDL (double current) models
- Teleprinter Model T 150 (electromechanical)
- Offline tape punch for creating messages
- Teleprinter T 1000 electronic teleprinter (processor based) 50-75-100 Bd. Tape punch and reader attachments ND/NDL/SEU V21modem model
- Teleprinter T 1000 Receive only units as used by newsrooms for unedited SAPA/Reuters/AP feeds etc.
- Teleprinter T 1200 electronic teleprinter (processor based) 50-75-100-200 Bd.Green LED text display, 1.44M 3.5" floppy disk ("stiffy") attachment
- PC-Telex Teleprinter with dedicated dot matrix printer Connected to IBM compatible PC (as used by Telkom South Africa)
- T4200 Teletex Teleprinter With two floppy disc drives and black and white monitor/daisy wheel typewriter (DOS2)
Teletype Corporation
The Teletype Corporation, a part of
Teletype machines tended to be large, heavy, and extremely robust, capable of running non-stop for months at a time if properly lubricated.[41] The Model 15 stands out as one of a few machines that remained in production for many years. It was introduced in 1930 and remained in production until 1963, a total of 33 years of continuous production. Very few complex machines can match that record. The production run was stretched somewhat by World War II—the Model 28 was scheduled to replace the Model 15 in the mid-1940s, but Teletype built so many factories to produce the Model 15 during World War II, it was more economical to continue mass production of the Model 15. The Model 15, in its receive only, no keyboard, version was the classic "news Teletype" for decades.
- Model 15 = Baudot version, 45 Baud, optional tape punch and reader
- Model 28 = Baudot version, 45-50-56-75 Baud, optional tape punch and reader
- Model 32 = small lightweight machine (cheap production) 45-50-56-75 Baud, optional tape punch and reader
- Model 33 = same as Model 32 but for 8 level ASCII-plus-parity-bit, used as computer terminal, optional tape punch and reader, 72 char./line.[42]
- Model 35 = same as Model 28 but for 8 level ASCII-plus-parity-bit, used as heavy-duty computer terminal, optional tape punch and reader
- Model 37 = improved version of the Model 35, higher speeds up to 150 Baud, optional tape punch and reader
- Model 38 = similar to Model 33, but for 132 char./line paper (14 inches wide), optional tape punch and reader
- Model 40 = new system processor based, w/ monitor screen, but mechanical "chain printer"
- Model 42 = new cheap production Baudot machine to replace Model 28 and Model 32, paper tape acc.
- Model 43 = same but for 8 level ASCII-plus-parity-bit, to replace Model 33 and Model 35, paper tape acc.
Several different high-speed printers like the "Ink-tronic" etc.
Texas Instruments
Texas Instruments developed its own line of teletypes in 1971, the Silent 700. Their name came from the use of a thermal printer head to emit copy, making them substantially quieter than contemporary teletypes using impact printing, and some such as the 1975 Model 745 and 1983 Model 707 were even small enough to be sold as portable units. Certain models came with acoustic couplers and some had internal storage, initially cassette tape in the 1973 Models 732/733 ASR and later bubble memory in the 1977 Models 763/765, the first and one of the few commercial products to use the technology.[43] In these units their storage capability essentially acted as a form of punched tape. The last Silent 700 was the 1987 700/1200 BPS, which was sold into the early 1990s.
Telex
A global teleprinter network called Telex was developed in the late 1920s, and was used through most of the 20th century for business communications. The main difference from a standard teleprinter is that Telex includes a switched routing network, originally based on pulse-telephone dialing, which in the United States was provided by Western Union. AT&T developed a competing network called "TWX" which initially also used rotary dialing and Baudot code, carried to the customer premises as pulses of DC on a metallic copper pair. TWX later added a second ASCII-based service using Bell 103 type modems served over lines whose physical interface was identical to regular telephone lines. In many cases, the TWX service was provided by the same telephone central office that handled voice calls, using class of service to prevent POTS customers from connecting to TWX customers. Telex is still in use in some countries for certain applications such as shipping, news, weather reporting and military command. Many business applications have moved to the Internet as most countries have discontinued telex/TWX services.
Teletypesetter
In addition to the 5-bit Baudot code and the much later seven-bit ASCII code, there was a six-bit code known as the Teletypesetter code (TTS) used by news wire services. It was first demonstrated in 1928 and began to see widespread use in the 1950s.[44] Through the use of "shift in" and "shift out" codes, this six-bit code could represent a full set of upper and lower case characters, digits, symbols commonly used in newspapers, and typesetting instructions such as "flush left" or "center", and even "auxiliary font", to switch to italics or bold type, and back to roman ("upper rail").[45]
The TTS produces aligned text, taking into consideration character widths and column width, or line length.
A Model 20 Teletype machine with a paper tape punch ("reperforator") was installed at subscriber newspaper sites. Originally these machines would simply punch paper tapes and these tapes could be read by a tape reader attached to a "Teletypesetter operating unit" installed on a Linotype machine. The "operating unit" was essentially a tape reader which actuated a mechanical box, which in turn operated the Linotype's keyboard and other controls, in response to the codes read from the tape, thus creating type for printing in newspapers and magazines.[46]
This allowed higher production rates for the Linotype, and was used both locally, where the tape was first punched and then fed to the machine, as well as remotely, using tape transmitters and receivers.
Remote use played an essential role for distributing identical content, such as
In later years the incoming 6-bit current loop signal carrying the TTS code was connected to a
Teleprinters in computing
Computers used teleprinters for input and output from the early days of computing.
Users typed commands after a
Paper tape was sometimes used to prepare input for the computer session off line and to capture computer output. The popular Teletype Model 33 used 7-bit ASCII code (with an eighth parity bit) instead of Baudot. The common modem communications settings, Start/Stop Bits and Parity, stem from the Teletype era.
In early operating systems such as Digital's RT-11, serial communication lines were often connected to teleprinters and were given device names starting with tt. This and similar conventions were adopted by many other operating systems. Unix and Unix-like operating systems use the prefix tty, for example /dev/tty13, or pty (for pseudo-tty), such as /dev/ptya0, but some of them (e.g. Solaris & recent Linux) have replaced pty files by a pts folder (where "pt" stands for "pseudoterminal" instead). In many computing contexts, "TTY" has become the name for any text terminal, such as an external console device, a user dialing into the system on a modem on a serial port device, a printing or graphical computer terminal on a computer's serial port or the RS-232 port on a USB-to-RS-232 converter attached to a computer's USB port, or even a terminal emulator application in the window system using a pseudoterminal device.
Teleprinters were also used to record fault printout and other information in some TXE telephone exchanges.
Obsolescence of teleprinters
Although printing news, messages, and other text at a distance is still universal, the dedicated teleprinter tied to a pair of leased copper wires was made functionally obsolete by the
In the 1980s, packet radio became the most common form of digital communications used in amateur radio. Soon, advanced multimode electronic interfaces such as the AEA PK-232 were developed, which could send and receive not only packet, but various other modulation types including Baudot. This made it possible for a home or laptop computer to replace teleprinters, saving money, complexity, space and the massive amount of paper which mechanical machines used.
See also
- Letter-quality printer
- Plan 55-A, a message switching system for telegrams
- Radioteletype
- Siemens and Halske T52 – the Geheimfernschreiber (secrets teleprinter)
References
- ^ Nelson, R.A., History Of Teletype Development, archived from the original on November 5, 2020
- ^ Roberts, Steven, Distant Writing
- Flexowriter [teletypewriter]… could function as a keyboard input device… Thus in 1955 MIT's Whirlwind[became] the first computer in the world to allow its users to enter commands through a keyboard…
- ^ Latifiyan, Pouya (Winter 2021). "Aeronautical Fixed Telecommunication network and surrounding technologies". Take off. 2. Civil Aviation Technology College.
- ^ a b "Typewriter May Soon Be Transmitter of Telegrams" (PDF), The New York Times, January 25, 1914
- ^ "Type used for original morse telegraph, 1835". Science Museum. Retrieved December 5, 2017.
Samuel Morse was one of the pioneers of electric telegraphy. Prompted by receiving news of his wife's death too late to attend her funeral, Morse was determined to improve the speed of long distance communications (which at that point relied on horse messengers).
- ^ Roberts, Steven. "3. Cooke and Wheatstone". Distant Writing: A History of the Telegraph Companies in Britain between 1838 and 1868.
- ^ Steven Roberts. "Distant Writing – Bain".
- ^ "Silent Key – Edward Kleinschmidt". RTTY Journal. 25 (9): 2. October 1977.
- ^ "David Edward Hughes". Clarkson University. April 14, 2007. Archived from the original on April 22, 2008. Retrieved September 29, 2010.
- ^ Hobbs, Alan G. "Five-unit codes". Retrieved May 1, 2012.
- The World's Work: A History of Our Time. Vol. II. pp. 1195–1199. Retrieved July 9, 2009.
- ^ US Patent 888335, issued May 1908
- ^ US Patent 862402
- ^ US Patent 1286351, issued December 1918
- ^ ISBN 9781579584641.
- ^ "Morkum Printing Telegraph Page Printer". Retrieved August 15, 2011.
- ^ US Patent 1448750, KLEINSCHMIDT, E., "TELEGRAPH PRINTER", issued Apr 14, 1916
- ^ US Patent 1463136, KLEINSCHMIDT, E., "METHOD OF AND APPARATUS FOR OPERATING PRINTING TELEGRAPHS", issued May 1, 1919
- ^ ISBN 0-471-20505-2.
- ISBN 3-327-00307-6.
- ^ Schamel, John (October 19, 2016). "Flight Service History 1920-1998". Air Traffic Control History.
- ^ "FAA HISTORICAL CHRONOLOGY, 1926-1996" (PDF). faa.gov. December 17, 2005. Archived from the original (PDF) on November 5, 2013.
- ^ "AP teletype machine". CBC History. Retrieved March 5, 2022.
- ^ US Patent 2364357, "Signaling system", issued 29 March 1944
- ^ "Introduction to RTTY" (PDF). Sam's Telecomms Documents Repository.
- ^ "RTTY Demodulators".
- ^ "ASR 33 Teletype Rear View of Main Assembly". www.pdp8online.com.
- ^ "TELETYPE MODEL 32ASR". www.k7tty.com.
- ^ Baudot.net: Creed & Company, Ltd.
- ^ "Gretag ETK-47 14-bit teleprinter system". Crypto Museum. July 4, 2016.
- ^ "ETK teletype equipment series".
- ^ F. Dörenberg. "Other manufacturers of teleprinter machines that use the Hellschreiber principle". Dr. Edgar Gretener AG (Gretag).
- ^ "The Hagelin - Gretener Cipher Teleprinter" (PDF).
- ISBN 9781579584641.
- ^ "Morkum Printing Telegraph Page Printer". Retrieved August 22, 2011.
- ^ a b "Queensland Telecommunications Museum – Teleprinters". Queensland Telecommunications Museum.
- ^ Earle, Ralph H. (1917). The Morkrum System of Printing Telegraphy. Chicago: Armour Institute of Technology (thesis).
- ^ "History of The Teletype Corporation". June 24, 2003. Archived from the original on June 3, 2008. Retrieved March 3, 2010.
- ^ "US trademark database". uspto.gov.
- ^ Adjustments, Type Bar Page Printer, (Model 15) (PDF). Chicago: Teletype Corporation. 1941. Archived from the original (PDF) on January 11, 2011.
- ^ "ASR 33 Teletype Information". www.pdp8online.com.
- ^ "Old Vintage Computing Research: Refurb weekend: Texas Instruments Silent 700 Model 745 teletype". February 17, 2022.
- ISBN 978-0-7864-1371-3.
- ^ Mergenthaler Linotype Company (1951). The Linotype Handbook for Teletypesetter Operation. Dr. David M. MacMillan. digital reprint by www.CircuitousRoot.com.
- ^ Doug Kerr. "Teletypes in Typesetting". Glendale, Arizona, USA: Southwest Museum of Engineering, Communications and Computation. Retrieved April 25, 2017.
Further reading
- Foster, Maximilian (September 1901). "A Successful Printing Telegraph". The World's Work. Vol. II, no. 5. New York: Doubleday, Page & Co. pp. 1195–1200. Retrieved April 29, 2012.
- Gannon, Paul (2006). Colossus: Bletchley Park's Greatest Secret. London: Atlantic Books. ISBN 978-1843543312. On the role of the teleprinter code in WWII
- A. G. Hobbs, G8GOJ; E. W. Yeomanson, G3IIR; A.C. Gee, G2UK (1983). Teleprinter handbook (2nd ed.). ISBN 0-900612-59-2.)
{{cite book}}
: CS1 maint: numeric names: authors list (link - "Teletype Messages Sent Through Switch Board". ISSN 0032-4558.
AT&T offering two way service through switchboards
External links
- A first-hand report of Teletype Corporation's early years Archived March 12, 2009, at the Wayback Machine
- A Gallery of Teletype Images
- History of Teletypewriter Development by R.A. Nelson
- "Some Notes on Teletype Corporation"
- Mass.gov: TTY explanation and government best practices for TTY use
Patents
- US Patent 1665594, "Telegraph printer (Type 12 Teletype)", issued April 1928
- US Patent 1745633, "Telegraph receiver (Type 14 Teletype)", issued February 1930
- US Patent 1904164, "Signalling system and apparatus therefor (Type 15 Teletype)", issued April 1933
- US Patent 3507997, "Frequency-Shift Teletypewriter", issued April 1970