Teleprinter

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teleprinter ( teletypewriter , Teletype or TTY ) is an electromechanical typewriter that can be used to send and receive typed messages via various communication channels, both in point-to-point and point-to-multipoint configuration. The machines were adapted to provide a user interface for early mainframe computers and mini computers, sending typed data to a computer and printing response. Some models can also be used to create perforated ribbons for data storage (either from typed input or from data received from remote sources) and to re-read the tape for local printing or transmission.

Teleprinters can use different communication media. This includes a pair of simple cables; dedicated non-switched telephone circuits (leased lines); replacing the network that operates the same as the public telephone network (telex); and radio and microwave links (telex-on-radio, or TOR). Telephrers attached to the modem can also communicate over a standard public phone line that is turned on. This latter configuration is often used to connect the teleprinter to a remote computer, especially in a time share environment.

Teleprinters have largely been replaced by fully electronic computer terminals that usually have computer monitors, not printers (although the term "TTY" is sometimes still used to refer to them, as in Unix systems). Teleprinters are still widely used in the aviation industry (see AFTN and airline teletype systems), and variations called Telecommunications Devices for the Deaf (TDDs) are used by hearing impaired for typed communications over regular telephone lines.

Video Teleprinter

Histori

Teleprinters evolved through a series of inventions by a number of engineers, including Samuel Morse, Alexander Bain, Royal Earl's House, David Edward Hughes, Emile Baudot, Donald Murray, Charles L. Krum, Edward Kleinschmidt and Frederick G. Creed. Teleprinters were created to send and receive messages without the need for operators trained in the use of Morse code. The two teleprinter system, with one operator trained to use a typewriter, replaced two trained Morse code operators. The teleprinter system increases message speed and delivery time, allowing messages to be flash in a country with minimal manual intervention.

In 1835, Samuel Morse made a telegraph recording, and Morse code was born.

In 1841 Alexander Bain compiled a printing telegraph.

In 1846, Morse telegraph service operated between Washington, D.C., and New York. Royal Earl House patented its printing telegraph in the same year. He connects two 28-key piano-style keyboards with cables. Each piano key represents the letter of the alphabet and when pressed causes the corresponding letter to be printed on the receiving end. The "shift" key gives each key two optional values. A 56-character typewheel at the sending end is synchronized to coincide with the same wheel at the receiving end. If a key associated with a particular character is pressed on the home station, it presses a key on a remote station as the same character moves to the printing position, in a manner similar to a daisy wheel printer. Thus an example of a synchronous data transmission system. Home appliances can deliver about 40 words that can be read quickly per minute, but are difficult to mass-produce. The printer can copy and print up to 2,000 words per hour. The discovery was first operated and exhibited at the Mechanics Institute in New York in 1844.

Operation of the ground teleprinter began in 1849, when a series operated between Philadelphia and New York City.

In 1855, David Edward Hughes introduced an enhanced engine built on the work of Royal Earl House. In less than two years, a number of small telegraph companies, including Western Union in the early stages of development, united to form one large company - Western Union Telegraph Co. - to run the telegraphy business on the Hughes system.

In France, ÃÆ'â € ° mile Baudot was designed in 1874 a system using a five-unit code, which became widely used in the country from 1877. The British Post Office adopted the Baudot system to be used on a simple circuit between London and Paris in 1897, and later utilizing many of the duplex Baudot systems on their Outback Telegraph Service.

During 1901, Baudot codes were modified by Donald Murray (1865-1945, originally from New Zealand), driven by the development of keyboards such as typewriters. The Murray system uses a transition step, a keyboard perforator, which allows the operator to punch paper tape, and a tape transmitter to send messages from hollow tape. At the receiving end, the printing mechanism will be printed on paper tape, and/or reaction apparatus can be used to make copies of hollow messages. Since there is no direct correlation between the operator's hand movements and transmitted bits, there is no concern about setting the code to minimize operator fatigue, and instead Murray designed the code to minimize wear on the machine, assigning a combination of code with the least holes to the most frequently used characters. The Murray Code also introduces what is known as "effector format" or "control character" - CR code (Traffic Returns) and LF (Feed Line). Some of the Baudot code moved to the position where they have lived since: NULL or BLANK and DEL codes. NULL/BLANK is used as a silent code when no messages are sent.

In the United States in 1902, electrical engineer Frank Pearne approached Joy Morton, head of Morton Salt, seeking sponsorship for research on the practicality of developing a telegraph printing system. Joy Morton needs to determine if this is useful and strongly consulted with engineer Charles L. Krum, who is vice president of Cold Cold Storage Company. Krum is interested in helping Pearne, so space is set up in a lab in the Western Cold Cold Storage attic. Frank Pearne lost interest in the project after a year and went to engage in teaching. Krum is ready to continue Pearne's work, and in August 1903 a patent was filed for a 'typebar page printer'. In 1904, Krum filed a patent for the 'wheel type telegraph machine' issued in August 1907. In 1906, Charles Krum's son, Howard Krum, joined his father in this work. It was Howard who developed and patented the start-stop synchronization method for the code telegraph system, which enabled the teleprinter to be practical.

In 1908, a working teleprinter was produced by the Morkrum Company, called the Morkrum Printing Telegraph, which was tested on the field with Alton Railroad. In 1910, the Morkrum Company designed and installed the first commercial teletypewriter system on the Telegraph line between Boston and New York using the "Blue Code Version" of the Morkrum Printing Telegraph.

In 1916, Edward Kleinschmidt applied for a patent for a typebar page printer. In 1919, shortly after the Morkrum company acquired their patent for a start-stop synchronization method for the code telegraph system, which enabled the practical teleprinter, Kleinschmidt submitted an application titled "Methods and Tools for Operational Printing Telegraph" that included a better start. -stop method. The basic start-stop procedure, however, is much older than that of Kleinschmidt and Morkrum. It was proposed by D'Arlincourt in 1870.

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 Morkrum-Kleinschmidt Company in 1924. This new company combines the best features of both their engines into a new typewheel printer. the Kleinschmidt, Howard Krum, and Sterling Morton jointly obtain the patent.

In 1924, Credo & amp; The company, founded by Frederick G. Creed, entered the teleprinter field with their Model 1P, a page printer, soon to be replaced by an improved 2P Model. In 1925 Creed obtained a patent for Murray Murray's code, a rudimentary Baudot code. The 3-tape model printer, the first combined start-stop engine Creed, was introduced in 1927 for the Post Office telegram service. This machine prints a received message directly onto a paper tape that is attached at a rate of 65 words per minute. Creed creates his first keyboard perforator, which uses compressed air to punch holes. He also created a reperforator (received perforator) and printer. The reperforator suppresses the Morse signal into the paper tape and the printer translates the tape to produce alphanumeric characters on plain paper. This is the origin of the Creed High Speed ​​Automatic Printing System, which can run with an unprecedented 200 words per minute. His system was adopted by the Daily Mail for daily transmission of newspaper contents. The Creed 7 Model page print adapter was introduced in 1931 and used for inland Telex services. It works at a speed of 50 baud, about 66 words per minute, using code based on Murray code.

The Teletype system was installed at the Aviation Station Aviation Station of the Airway Radio Station in 1928, carrying administrative messages, flight information and weather reports. In 1938, the FAA Teletype network, handling weather traffic, extended over 20,000 miles, covering 48 countries except Maine, New Hampshire and South Dakota.

Maps Teleprinter

The way in which the teleprinter is used

There are at least five main types of teleprinter networks:

• Exchange systems like Telex and TWX. This creates real-time circuits between two machines, so anything typed on one machine appears on the other end immediately. The US and UK systems had real phones, and before 1981 five US area codes were reserved for teletype use; The German system does a "call" through the keyboard. Typed "chat" is possible, but since billing is done through connection time, you usually set up a message on a paper tape and send it without pause to type.
• Leased line and radioteletype networks are arranged in point-to-point and/or multipoint configurations to support data processing applications for government and industry such as integrating accounting, billing, management, production, purchasing, sales, delivery and acceptance of departments within an organization to speed up internal communication.
• Message diversion system. This is the initial form of E-mail, done with electromechanical equipment. See Telegram, Western Union, Plan 55-A. Military organizations have a similar but separate system. See Autodin.
• Broadcasting systems such as distribution of weather information and "news cable". See Associated Press, National Weather Service, Reuters, and United Press (then UPI). News received in receiver only teleprinter only, no keyboard or fast.
• "Loop" system, where there is typed on any machine on the circle that is printed on all machines. The police department uses such a system to connect the surrounding area.

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Teleprinter operation

Most telephrers use 5-bit International Telegraph Alphabet No. 2 (ITA2). This limited character is set to 32 codes (2 ⁵ = 32). One should use the "FIGS" shift key to type numbers and special characters. The special version of the teleprinter has FIGS characters for specific apps, such as weather symbols for weather reports. Print quality is poor by modern standards. The ITA2 code is used asynchronously with start and stop bits: asynchronous code design is closely related to the start-stop design of electro-mechanical teleprinters. (The initial system has been using sync code, but it is difficult to synchronize mechanically). Other codes, such as FIELDATA and Flexowriter, were introduced but never became as popular as ITA2.

Mark and space are terms that describe the logic level in the teleprinter circuit. The original mode of communication for the teleprinter is a series of distorted simple DC circuits, just like the dial that interrupts the telephone signal. The marking condition is when the circuit is closed (current flows), the distance condition is when the circuit is open (no current flows). The "idle" state of the circuit is a state of continuous tagging, with the commencement of characters marked by "start bit", which is always space. Following the initial bit, the characters are represented by a fixed number of bits, such as 5 bits in the ITA2 code, each of which either marks or spaces to indicate a particular character or machine function. After the character bits, the sending machine sends one or more stop bits. Stop bit marking, so it's different from the next start bit. If the sender has nothing else to send, the line remains in the tagging state (as if it were a continuous series of stop bits) until the next space indicates the beginning of the next character. The time between characters need not be an integral combination of less time, but must be at least the minimum number of stop bits required by the receiving machine.

When the line is broken, the continuous distance (open circuit, no current flow) causes the receiver teleprinter to cycle continuously, even in the absence of a stop bit. Does not print anything because the received characters are all zeros, empty characters ITA2 (or ASCII) null.

Teleprinter circuits are generally rented from public communications carriers and consist of ordinary telephone cords extended from the teleprinter located at the customer's premises to the general operator's headquarters. This teleprinter circuit is connected to switching equipment at headquarters for Telex and TWX services. The personal teleprinter line circuit is not connected directly to the switching equipment. Instead, these private line circuits are connected to network hubs and repeaters that are configured to provide point-to-point or point to multi-point services. More than two teleprinter can be connected to the same wire circuit through the current loop.

The previous teleprinter had three rows of keys and only supported uppercase. They use ITA2 code 5 bits and generally work on 60 to 100 words per minute. Later teleprinters, specifically Teletype Model 33, used the ASCII code, an innovation that began to be widely used in the 1960s as computers became more widely available.

"Speed", intended to be roughly proportional to the word per minute, is a standard term introduced by Western Union for the rate of mechanical teleprinter data transmission using the popular 5-bit ITA2 code in the 1940s and for decades thereafter. Such a machine would send an initial 1 bit, 5 data bits, and a 1.42 bit stop. This unusual stop time bit is actually a break period to allow mechanical printing mechanisms to sync in case the damaged signal is received. This is especially true on high frequency radio circuits where selective fading is present. Selective fading causes the amplitude of the mark signal to be randomly different from the amplitude of the space signal. Selective fading, or Rayleigh fading can cause two randomly and independently operators to fade to different depths. Since modern computer equipment can not easily generate 1.42 bits for stopping periods, the common practice is to estimate this by 1.5 bits, or sending 2.0 bits when receiving the received 1.0 bits.

For example, the "speed 60" engine is directed at 45.5 baud (22.0 ms per bit), the "speed 66" engine is directed at 50.0 baud (20.0 ms per bit), the "75 acceleration" engine is directed at 56 , 9 baud. (17.5 ms per bit), the "100 speed" engine is designed at 74.2 baud (13.5 ms per bit), and the "133 speed" engine is designed at 100.0 baud (10.0 ms per bit). Speed ​​60 became the de facto standard for the operation of RTTY radio amateurs due to the widespread availability of equipment at that speed and the US Federal Communications Commission's restrictions only 60 speeds from 1953 to 1972. Telex, cable news agencies and Similar services generally use 66 speed services. There are several migrations to speeds of 75 and 100 when more reliable devices are introduced. However, HF transmission limitations such as excessive error rates due to multipath distortion and ionosphere propagation properties make many users at speeds of 60 and 66. Most recent Teletype audio recordings are teleprinters operating at 60 words per minute, and most of the Teletype Model 15.

Another measure of Teletype machine speed is the total "per minute (OPM)" operation. For example, 60 speed is usually 368 OPM, 66 speed is 404 OPM, 75 speed is 460 OPM, and 100 speed is 600 OPM. Western Union Telexes is usually set at 390 OPM, with 7.0 bits total rather than the usual 7.42 bits.

Both wire-service and private teleprinters have bells for important incoming message signals and can ring 24/7 when power is turned on. For example, ringing 4 bells on UPI's wire-service machine means "Urgent" message; 5 bells are "Bulletins"; and 10 bells is FLASH, used only for very important news, such as the assassination of John F. Kennedy.

The teleprinter circuit is often associated with a 5-bit (or "reperforator") paper tape and reader, allowing messages received to hate in other circuits. Complex military and commercial communications networks are built using this technology. Message centers have teleprinter rows and large shelves for paper cassettes waiting for transmission. A trained operator can read the priority code of the hole pattern and may even feed "FLASH PRIORITY" to the reader while it's still out of the blow. Routine traffic often has to wait for hours to relay. Many teleprinters have a built-in paper tape reader and punch, allowing messages to be stored in machine-readable form and edited off-line.

Radio communication, RTTY, is also common. Amateur radio operators continue to use this communication mode today.

Control characters

The typewriter or the electromechanical printer can print characters on paper, and perform operations such as moving the carriage back to the left margin of the same line (carriage return), progressing to the same column of the line feed, and so on.. Commands to control non-print operations are transmitted in exactly the same way as printable characters by sending control characters to the specified function (eg, line feed characters forcing the train to move to the same position on the next line ) to teleprinters. In modern computing and communications, some control characters, such as carriage return and line feeds, have retained their original function (though often implemented in software rather than activating electromechanical mechanisms to move physical carriage carts) but many others are no longer needed and used for other purposes.

Answer the mechanism again

Some teleprinters have a "Here is" key, which transmits a fixed sequence of 20 or 22 characters, programmed by splitting the drum tab. This sequence can also be sent automatically after receiving ENQ signal (control E), if enabled. This is usually used to identify stations; the operator can press the button to send the station identifier to the other end, or the remote station can trigger transmission by sending an ENQ character, basically asking "who are you?"

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Manufacturer

Creed & amp; Company

Creed & amp; The company, an English company, built a teleprinter for the GPO teleprinter service.

• Creed model 7E (with overlap cam and range finder)
• Model 7B Credits
• Model Credo 7
• Creed model 7/RP (reperforator teleprinter)
• Model Creed 54
• Model Creed 75
• Model Creed 85 (reperforator)
• Creed model 86 (reperforator)
• Creed Model 444 (GPO type 15)

Kleinschmidt Labs

In 1931 Edward Kleinschmidt formed Kleinschmidt Labs to pursue different types of Teletype designs. In 1944 Kleinschmidt demonstrated its lightweight units to Signal Corps and in 1949 their designs were adopted for the portable needs of the Army. In 1956, Kleinschmidt Labs merged with Smith-Corona, who later joined Marchant Calculating Machine Co., forming SCM Corporation. In 1979, the Kleinschmidt division branched into Electronic Data Interchange, a business where they became very successful, and replaced mechanical products, including teleprinters.

The Kleinschmidt machine, with the military as their primary customer, uses standard military designations for their machines. Teleprinter is identified with titles such as TT-4/FG, while teleprinter "set" communications may be a common part using a standard Army/Navy designation system such as AN/FGC-25. These include Kleinschmidt TT-117/FG teleprinter and TT-179/FG tape reperforator.

Morkrum

Morkrum made the first commercial installation of telegraph printing with the Postal Telegraph Company in Boston and New York in 1910. Became popular with railroads, and the Associated Press adopted it in 1914 for their wire services. Morkrum joined their competitor Kleinschmidt Electric Company to become Morkrum-Kleinschmidt Corporation shortly before being renamed Teletype Corporation.

Olivetti

Italian office equipment maker Olivetti (est. 1908) began producing teleprinters to provide Italian post office with modern equipment to send and receive telegram. The first model is typed on a paper ribbon, which is then cut and glued to a telegram form.

• Olivetti T1 (1938-1948)
• Olivetti T2 (1948-1968)
• Olivetti Te300 (1968-1975)
• Olivetti Te400 (1975-1991)

Siemens & amp; Halske

Siemens & amp; Halske, then Siemens AG, a German company, was founded in 1897.

• Teleprinter Model 100 Ser 1 (end of 1950s) Ã, - Used for Telex service
• Teleprinter Model 100 Ser. 11 - The next version with minor changes
• Model Teleprinter T100 ND (one current) NDL (dual current)
• Model T 150 (electromechanical) Teleprinter
• Tap an offline tape to create a message
• Teleprinter T 1000 electronic teleprinter (processor based) 50-75-100 Bd. Tape punch and attachment reader 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. LED green text display, 1.44M 3.5 "floppy disk (" rigid ") attachment
• PC-Telex Teleprinter with a dedicated dot matrix printer Connected to an IBM compatible PC (as used by Telkom South Africa)
• T4200 Teletex Teleprinter With two floppy disk drives and black/white monitor/daisy wheel typewriter (DOS2)

Teletype Corporation

The Teletype Corporation , part of American Telephone and Telegraph Company Western Electric manufacturing arm since 1930, was founded in 1906 as the Morkrum Company. In 1925, the merger between Morkrum and Kleinschmidt Electric Company created the Morkrum-Kleinschmidt Company. The name was changed in December 1928 to Teletype Corporation. In 1930, Teletype Corporation was purchased by American Telephone and Telegraph Company and became a subsidiary of Western Electric. In 1984, the Bell System divestment resulted in the name Teletype and logo replaced by the name and logo of AT & amp; ultimately resulting in a brand that goes out. The last remnants of what Teletype Company had ceased in 1990, bringing to near a dedicated teleprinter business. Despite its long-lasting trademark status, the word Teletype is commonly used in the news and telecommunications industry. Records of the United States Patent and Trademark Office indicate that the trademark has expired and is considered dead.

Teletype machines tend to be large, heavy, and very powerful, able to walk non-stop for months at a time if properly lubricated. Model 15 stands out as one of the few machines that have remained manufactured for years. It was introduced in 1930 and remained manufactured until 1963, a total of 33 years of continuous production. Very few complex machines can match the record. Production runs somewhat spanned by World War II - Model 28 was scheduled to replace Model 15 in the mid-1940s, but Teletype built so many factories to produce Model 15 during World War II, it was more economical to continue mass production of Model 15. Model 15, in which receive only, without a keyboard, the version is the classic "news Teletype" for decades.

• Model 28 = Baudot Version, 45-50-56-75 Baud, optional tape player and reader
• Model 32 = small light machine (cheap production) 45-50-56-75 Baud, optional paper punching device and reader
• Model 33 = the same as Model 32 but for 8 ASCII-plus-parity-bit levels, used as computer terminal, punch tape and optional reader
• Model 35 = the same as Model 28 but for 8 ASCII-plus-parity-bit levels, used as heavy duty computer terminal, optional paper punching tool and reader
• Model 37 = improved version of Model 35, higher speed up to 150 Baud, optional paper punching tool and reader
• Model 38 = similar to Model 33, but for 132 char./line paper (14 inches wide), optional punch and reader tape
• Model 40 = new system processor base, w/monitor screen, but mechanical "chain printer"
• Model 42 = The new low cost Baudot production machine to replace the Model 28 and Model 32, paper tape acc.
• Model 43 = same but for 8 ASCII-plus-parity-bit levels, to replace Model 33 and Model 35, access paper tape.

Some different high-speed printers like "Ink-tronic" etc.

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Telex

The global teleprinter network, called the "Telex network", was developed in the late 1920s, and was used for most of the 20th century for business communications. The main difference from standard teleprinter is that Telex includes switched routing networks, originally based on pulse phone calls, which in the United States are provided by Western Union. AT & amp; T developed a competing network called "TWX" which originally also used a rotary play and Baudot code, brought to the customer's place as a DC pulse on a metal copper pair. TWX then added a second ASCII-based service using Bell 103 type modem presented over a channel whose physical interface is identical to ordinary telephone lines. In many cases, the TWX service is provided by the same telephone headquarters that handles voice calls, using service classes to prevent POTS customers from connecting to TWX customers. Telex is still used in some countries for specific applications such as delivery, news, weather reports, and military command. Many business applications have moved to the Internet because most countries have stopped telex/TWX services.

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Teletypesetter

In addition to the 5-bit Baudot code and the next seven-bit ASCII code, there is a six-bit code known as the Teletypesetter (TTS) code used by the news wire service. It was first shown in 1928 and began to be widely used in the 1950s. Through the use of "shift in" and "shift out" codes, these six-bit codes can represent the full set of uppercase and lowercase characters, digits, commonly used symbols in newspapers, and limited letters such as "flush left" or " center".

The Teletype Model 20 machine with paper tape punch ("reperforator") is installed on the customer's newspaper site. Initially this machine will only punch paper cassettes and these tapes can be read by the tape reader attached to the "Teletypesetter operating unit" installed on the Linotype machine. "Operating unit" is basically a full box of solenoids located on the type of Linotype keyboard and pressing the corresponding button in response to the code read from the cassette, thus creating the type to be printed in newspapers and magazines.

In later years, an incoming 6-bit signal loop signal carrying a TTS code is connected to a mini-computer or mainframe for storage, editing, and feeds eventually to the phototypesetting machine.

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Teleprinter in computing

Computers use teleprinters for input and output from the early days of computing. Beaten card readers and fast printers replaced teleprinters for most purposes, but teleprinters continued to be used as interactive time-sharing terminals until video display became widely available in the late 1970s.

The user typed a command after the prompt character was printed. Printing is not unidirectional; if the user wants to delete what has been typed, the character is further printed to indicate that the previous text has been canceled. When the first video view is available, the user interface is initially the exact same as the electromechanical printer; expensive and rare video terminals can be used interchangeably with teleprinters. This is the origin of the text terminal and command line interface.

Paper tape is sometimes used to prepare inputs for off line computer sessions and to capture computer output. The popular Model Teletype 33 uses a 7-bit ASCII code (with an eighth parity bit) than Baudot. Common modem communication settings, Start/Stop Bits and Parity, are from the Teletype era.

In early operating systems like RT-11 Digital, serial communication lines are often connected to the teleprinter and are named devices that begin with tt . This and similar conventions are adopted by many other operating systems. Unix and Unix operating systems use the tty prefix, for example /dev/tty13 , or pty (for pseudo-tty), such as /dev/ptya0 . In many computing contexts, "TTY" has become the name for any text terminal, such as an external console device, user calling into the system on a modem on serial port device, print or graphical computer terminal on computer serial port or RS-232 port on converter USB-to-RS-232 connected to a computer's USB port, or even a terminal emulator application in a windows system using a pseudoterminal device.

Teleprinters are also used to record error prints and other information in some TXE phone exchanges.

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Exposure teleprinter

While printing news, messages, and other texts at a certain distance is still universal, a special teleprinter attached to a pair of brass cable rentals is made functionally obsolete by fax, personal computer, inkjet printer, email, and the Internet.

In the 1980s, packet radio became the most common form of digital communication used in amateur radio. Soon, sophisticated multimode electronic interfaces such as the AEA PK-232 were developed, which can send and receive not only packets, but various other modulation types including Baudot. This allows the home computer or laptop to replace the teleprinter, saving money, complexity, space and the large amount of paper used mechanical machines.

As a result, by the mid-1990s, the use of amateurs from the actual Teletype machine had faded, although the core of "purists" still operated on equipment originally produced in the 1940s, 1950s, 1960s and 1970s.

Despite the obsolescence of teleprinters in the 21st century, its distinctive voice continues to be played in the background of newscasts on New York City, WINS, and KYW Philadelphia radio stations, a tradition that began in the mid-1960s.

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See also

• Mail quality printers
• Package 55-A, messaging system for telegram.
• Radioteletype
• Siemens and Halske T52 - Geheimfernschreiber ( teleprinter secrets )

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References

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Further reading

• "Teletype Message Sent via Switch Board", Popular Mechanics , April 1932. Offers & two services via switchboard
• A.G. Hobbs, G8GOJ; E.W. Yeomanson, G3IIR; AIR CONDITIONING. Gee, G2UK (1983). Teleprinter Handbook (2nd ed.). RSGB. ISBN: 0-900612-59-2.
• Foster, Maximilian (September 1901). "A Telegraph Printing Success". World Jobs . Vol.Ã, II no.Ã, 5. New York, NY: Doubleday, Page & amp; Co pp.Ã, 1195-1200 . Retrieved April 29, 2012 .
• Gannon, Paul (2006). Colossus: Bletchley Park's Greatest Secret . London. ISBN: 978-1843543312. Ã, on the role of teleprinter code in World War II

src: www.cryptomuseum.com

External links

• First hand report of Teletype Corporation's earliest years
• Teletype Image Gallery
• History of Teletypewriter Development by R.A. Nelson
• "Some Notes on Teletype Corporation"
• Mass.gov: TTY explanation and government best practices for TTY use

Patent

• AS. Patent 1,665,594 "Telegraph printer" (Type 12 Teletype), filed June 1924, issued April 1928
• AS. Patent 1,745,633 "Telegraph receiver" (Type 14 Teletype), filed in December 1924, published February 1930
• AS. Patent 1,904,164 "The system and signaling apparatus for it" (Type 15 Teletype) - filed in July 1930, issued in April 1933
• AS. Patent 3,507,997 "Frequency-Shift Teletypewriter" - filed in August 1966, issued April 1970

Source of the article : Wikipedia