A teleprinter (teletypewriter, Teletype or TTY for TeleTYpe/TeleTYpewriter) is a now largely obsolete electro-mechanical typewriter which can be used to communicate typed messages from point to point through a simple electrical communications channel, often just a pair of wires. A typewriter is a mechanical or Electromechanical device with a set of "keys" that when pressed cause characters to be printed on a medium
The most modern form of these devices are fully electronic and use a screen instead of a printer. These teletypewriters are still in use by the deaf for typed communications over the telephone, usually called a TDD (Telecommunications Devices for the Deaf) or TTY (although TTY, as indicated in the previous paragraph, refers to teleprinters in general). A telecommunications device for the deaf ( TDD) is an electronic device for text communication via a Telephone line used when one or more of the parties has hearing
The teleprinter evolved through a series of inventions by a number of engineers, including Royal Earl House, David E. Hughes, Edward Kleinschmidt, Charles Krum, Emile Baudot and Frederick G. Creed. Royal Earl House ( September 9, 1814 - February 25, 1895) was the inventor of the first David Edward Hughes ( 16 May 1831 &ndash 22 January 1900) coinventor of the Microphone, and an accomplished Welsh musician Kleinschmidt Inc is an EDI Pioneer Established in 1898 is the largest privately owned firm dedicated to exclusively providing network-based electronic commerce EDI ( Electronic Charles L Krum was a key figure in the development of the Teletype, a machine which played a key role in the history of Telegraphy and Computing. Jean-Maurice-Émile Baudot, ( September 11 1845 &ndash March 28 1903) French telegraph engineer and inventor Frederick George Creed (1871–1957 was a Canadian inventor who worked in the field of telecommunications and played an early role in the development of SWATH vessels A predecessor to the teleprinter, the stock ticker machine, was used as early as the 1870s as a method of displaying text transmitted over wires. Ticker tape was used by ticker tape machines, the Ticker tape timer stock ticker machines, or just stock tickers. A specially-designed telegraph typewriter was used to send stock exchange information over telegraph wires to the ticker machines. A stock exchange, share market or bourse is a Corporation or Mutual organization which provides "trading" facilities for Stock
Most teleprinters used the 5-bit Baudot code (also known as ITA2). The Baudot code, invented by Émile Baudot, is a character set predating EBCDIC and ASCII, and the root predecessor to International Telegraph The Baudot code, invented by Émile Baudot, is a character set predating EBCDIC and ASCII, and the root predecessor to International Telegraph This limited the character set to 32 codes. One had to use a "FIGS" shift key to type numbers and special characters. The shift key is a Modifier key on a keyboard, used to type capital letters and other alternate "upper" characters Special versions had FIGS codes for specific applications like weather reports. Print quality was poor by modern standards. The Baudot code was used asynchronously with start and stop bits: the asynchronous code design was intimately linked with the start-stop electro-mechanical design of teleprinters. Asynchronous serial communication describes an asynchronous, serial transmission protocol in which a start signal is sent prior to each byte character or code word (Early systems had used synchronous codes, but were hard to synchronise mechanically). Other codes, such as Fieldata and Flexowriter, were introduced but never became as popular as Baudot. Fieldata was a pioneering computer project run by the US Army Signal Corps in the late 1950s that intended to create a single standard for collecting and distributing The Friden Flexowriter, or flexowriter as on its nameplate was a Teleprinter, a heavy duty electric typewriter capable of being driven not only by a human typing
Mark and space are terms describing logic levels in Teletype circuits. In Digital circuits a logic level is one of a finite number of states that a signal can have The native mode of communication for a Teletype is a simple series DC circuit that is interrupted, much as a rotary dial interrupts a telephone signal. Within Electrical engineering, a DC circuit is an Electrical circuit that consists of any combination of constant Voltage sources constant current The rotary dial is a device mounted on or in a Telephone or switchboard that is designed to send interrupted electrical pulses, known as Pulse dialing The marking condition is when the circuit is closed, the spacing condition is when the circuit is open. The start of a character is signalled by a space. The stop bits are marking, so as to be distinct from the subsequent start bit. When the line is broken, a Teletype cycles continuously but prints nothing because it is receiving all zeros, the ASCII (or Baudot) null character. American Standard Code for Information Interchange ( ASCII) The null character (also null terminator) is a character with the value zero present in the ASCII and Unicode character sets and available Each Teletype circuit was leased from AT&T and consisted of twisted pair copper wires through ordinary telephone cables. Twisted pair Cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out Electrical wiring in general refers to insulated conductors used to carry Electricity, and associated devices These Teletype circuits were wired in series but were not connected to telephone switches.
The Teletype circuit was often linked to a paper tape punch (or "reperforator") and reader, allowing messages received to be resent on another circuit. Punched tape or paper tape is a largely obsolete form of Data storage, consisting of a long strip of paper in which holes are punched to store data Complex military and commercial communications networks were built using this technology. Message centers had rows of teleprinters and large racks for paper tapes awaiting transmission. Skilled operators could read the priority from the hole pattern and might even feed a "FLASH PRIORITY" tape into a reader while it was still coming out of the punch. Routine traffic often had to wait hours for relay. Many teleprinters had built-in paper tape readers and punches, allowing messages to be created and edited off-line.
More than two teleprinters could be connected to the same wire circuit by means of a current loop. A current loop describes two different electrical signalling schemes Communication by radio, RTTY, was also common. Radioteletype ( RTTY) is a Telecommunications system consisting of two or more Teleprinters using Radio as the Transmission medium. Amateur radio operators still use this mode of communication. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications
Teletype was a trademark of the Teletype Corporation of Skokie, Illinois, USA. Skokie (formerly Niles Center is a Village in Cook County, Illinois, United States. The predecessor Morkrum Company was founded in 1906 by Charles Krum and Mr. Joy Morton (of Morton Salt). Morton Salt is a United States company producing Salt for food water conditioning industrial agricultural and road/highway use They made their first commercial installation of a printing telegraph with the Postal Telegraph Company in Boston and New York in 1910. New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous It became popular with railroads, and the Associated Press adopted it in 1914 for their wire service. The Associated Press ( AP) is an American News agency. The AP is a Cooperative owned by its contributing Newspapers radio Morkrum merged with their competitor E. E. Kleinschmidt to become Morkrum-Kleinschmidt Corporation shortly before being renamed the Teletype Corporation. The company became part of AT&T in 1930. Before proposing a merge request please see Talk and see if the merger you propose has recently been made and The last vestiges of what had been Teletype Corporation ceased in 1990. 
The two parts kept their own peculiar design styles. "Teletype" machines tended to be large, heavy, and extremely robust-- capable of running non-stop for months at a time. In particular the Model 15 and Model 28 lines had very strong cast-iron frames, heavy-duty mechanisms, and heavy sound-proofed cases. The "Kleinschmidt" line tended to be somewhat more typewriter-like-- lighter, quieter-- more aluminum and less iron.
Teletype machines were given a model number, often modified by letters indicating the configuration:
Teletype Corporation documents invariably prefixed the configuration to the model number, e. g. "M33ASR" (Model 33 Automatic Send and Receive). In contrast, some customers and users tended to place the configuration before the model number, e. g. "ASR-33".
Major models and their dates:
Earlier Teletype machines had 3 rows of keys and only supported upper case letters. Introduced about 1963, Teletype Corporation 's ASR33 was a very popular model of Teleprinter. The system console, root console or simply console is the text entry and display device for system administration messages particularly those from the BIOS A minicomputer (colloquially mini) is a class of multi-user Computers that lies in the middle range of the computing spectrum in between the largest Multi-user The Switching Control Center System was an Operations Support System developed by Bell Laboratories and deployed during the early 1970s A dot matrix printer or impact matrix printer refers to a type of Computer printer with a print head that runs back and forth on the page and prints by impact striking They used the 5 bit baudot code and generally worked at 60 words per minute. The Baudot code, invented by Émile Baudot, is a character set predating EBCDIC and ASCII, and the root predecessor to International Telegraph Teletypes with ASCII code were an innovation that came into widespread use in the same period as computers began to become widely available.
Speed, intended to be roughly comparable to words per minute, was the standard designation introduced by Western Union for a mechanical teleprinter data transmission rate using the 5-bit baudot code that was popular in the 1940s and for several decades thereafter. Words per minute, commonly abbreviated wpm, is a measure of input or output speed The Western Union Company ( is a financial services and communications company based in the United States. The Baudot code, invented by Émile Baudot, is a character set predating EBCDIC and ASCII, and the root predecessor to International Telegraph Such a machine would send 1 start bit, 5 data bits, and 1. 42 stop bits. This unusual stop bit time was actually a rest period to allow the mechanical printing mechanism to recycle. 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. In Telecommunications and Electronics, baud (ˈbɔːd unit symbol "Bd" is synonymous to symbols/s or pulses/s. 0 ms per bit), a 66 speed machine is geared at 50. A millisecond (from Milli- and Second; abbreviation ms is one thousandth of a Second. 0 baud (20. In Telecommunications and Electronics, baud (ˈbɔːd unit symbol "Bd" is synonymous to symbols/s or pulses/s. 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 FCC restrictions to only 60 speed from 1953 to 1972. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications Radioteletype ( RTTY) is a Telecommunications system consisting of two or more Teleprinters using Radio as the Transmission medium. Telex, news agency wires and similar services commonly used 66 speed services. News agency (alternative A news agency is an organization of Journalists established to supply News reports to organizations in the News trade 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 Teletype sound effects in existence today are at 60 speed, and mostly of the Model 15. For the album by The Jam see Sound Affects. Sound effects or audio effects are artificially created or enhanced Sounds
Another measure of the speed of a Teletype machine 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.
A major difference should be noted between the majority of "teletypes" and the Model 26, 32, 33 and 38 series. All the older teletypes were built for heavy-duty 24-hour continuous use with only occasional oiling and cleaning, and an eventual lifetime of tens of thousands of hours until completely worn out. By contrast, the Model 26, 32, 33, and 38s were designed for light-duty use, just a few hours a day, and wearing out beyond economical refurbishment in just a few thousand hours. The older models were built with long-lasting parts: steel levers, ball-bearings, cast-iron frames. The 26, 32, 33, and 38 were mostly mazak ("monkey-metal") castings, thin levers, plastic gears, and plastic cases.
The Model 15 stands out as one of a few machines that remained in production for many many decades. It was introduced in 1935 and remained in production until 1963, a total of 28 years of continuous production. Very few complex machines can match that record. To be fair, 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 Model 15s for another couple of decades.
There were about 100,000 33-ASR Teletypes made in total. Now any personal computer equipped with a serial port can emulate the functionality of a Teletype. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated In Computing, a serial port is a Serial communication physical interface through which information transfers in or out one Bit at a time (contrast About the only feature that was required by Teletypes that has been generally abandoned is that a real Teletype required two stop bits to work reliably, so that each ASCII character (7 bits plus one parity bit) took 11 bit times. American Standard Code for Information Interchange ( ASCII) Error detection If an odd number of bits (including the parity bit are changed in transmission of a set of bits then parity bit will be incorrect and will thus indicate This is why 100 word per minute Teletypes transmitted at 110 baud. Today, most asynchronous serial data connections use one stop bit.
Both wire-service and private teletypes 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 11 bells was a FLASH, used only for very important news.
A global teleprinter network, called the Telex network, was established in the 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. Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information 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. The Bell 103 modem was the first commercial Modem for Computers released by AT&T in 1962. 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. The Internet is a global system of interconnected Computer networks
In addition to the 5-bit Baudot code and the much later eight-bit ASCII code, there was a six-bit code known as the TTS code (TeleTypeSetter) used by news wire services. A Model 20 Teletype machine with a punch ("reperforator") was installed at subscriber newspaper sites. Originally these machines would simply punch paper tapes and these tapes could be fed directly to a suitably equipped Linotype machine. The Linotype machine (pronounced "Line-O-Type") is a "line casting" machine used in Printing. In later years the incoming 6-bit current loop signal was coupled directly into a minicomputer or mainframe for editing and eventual feed to a phototypesetting machine.
Some of the earliest computers (for example, the LGP-30) used teleprinters for input and output. LGP-30, standing for Librascope General Purpose and then Librascope General Precision, was an early "off the shelf" computer manufactured by the Librascope Teleprinters were also used as the first interactive computer terminals. A computer terminal is an electronic or electromechanical hardware device that is used for entering data into and displaying data from a Computer or a Computing They had no video display. A visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video Users typed commands after a prompt character appeared. This was the origin of the text terminal and the command line interface. A computer terminal is an electronic or electromechanical hardware device that is used for entering data into and displaying data from a Computer or a Computing The paper tape function was sometimes used to prepare input for the computer session offline, or to capture computer output. The popular ASR33 teletype used 7-bit ASCII code (with an eighth parity bit) instead of Baudot. Introduced about 1963, Teletype Corporation 's ASR33 was a very popular model of Teleprinter. American Standard Code for Information Interchange ( ASCII) Error detection If an odd number of bits (including the parity bit are changed in transmission of a set of bits then parity bit will be incorrect and will thus indicate The common modem communications settings, Start/Stop Bits and Parity, stem from the teletype era. Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information
In computing, especially under Unix and Unix-like operating systems, teletypewriter has become the name for any text terminal, like an external console device, a user dialing in to 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 pseudo terminal device. Computing is usually defined like the activity of using and developing Computer technology Computer hardware and software. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination The system console, root console or simply console is the text entry and display device for system administration messages particularly those from the BIOS Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information In Computing, a serial port is a Serial communication physical interface through which information transfers in or out one Bit at a time (contrast A computer terminal is an electronic or electromechanical hardware device that is used for entering data into and displaying data from a Computer or a Computing In Telecommunications, RS-232 (Recommended Standard 232 is a standard for serial binary data signals connecting between a DTE ( Data Terminal Equipment A terminal emulator, terminal application, term, or tty for short is a program that emulates a "dumb" video terminal within some other In Unix, a pseudo terminal is a Pseudo-device pair that provides a Text terminal interface without associated virtual console, Computer Such devices have the prefix tty, such as /dev/tty13, or pty (for pseudo-tty), such as /dev/ptya0. An affix is a Morpheme that is attached to a stem to form a word
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 Fax, personal computer, inkjet printer, broadband, and the Internet. Fax (short for facsimile, from Latin fac simile, "make similar" i A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated Inkjet printers operate by propelling variably-sized droplets of liquid or molten material ( Ink) onto almost any sized page The term broadband can have different meanings in different contexts The Internet is a global system of interconnected Computer networks