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Teleprinter

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   Device for transmitting messages in written form by electrical signals
   "Teletype" redirects here. For other uses, see Teletype
   (disambiguation).
   For the telecommunications system consisting of teleprinters connected
   by radio, see Radioteletype.

   Teletype teleprinters in use in England during World War II
   Example of teleprinter art: a portrait of Dag Hammarskjoeld, 1962

   A teleprinter (teletypewriter, teletype or TTY) is an electromechanical
   device that can be used to send and receive typed messages through
   various communications channels, in both point-to-point and
   point-to-multipoint configurations. Initially they were used in
   telegraphy, which developed in the late 1830s and 1840s as the first
   use of electrical engineering,^[1] though teleprinters were not used
   for telegraphy until 1887 at the earliest.^[2] The machines were
   adapted to provide a user interface to early mainframe computers and
   minicomputers, sending typed data to the computer and printing the
   response. Some models could also be used to create punched tape for
   data storage (either from typed input or from data received from a
   remote source) and to read back such tape for local printing or
   transmission.

   Teleprinters could use a variety of different communication media.
   These included a simple pair of wires; 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). A teleprinter attached to a modem could also
   communicate through standard switched public telephone lines. This
   latter configuration was often used to connect teleprinters to remote
   computers, particularly in time-sharing environments.

   Teleprinters have largely been replaced by fully electronic computer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),^[3] and
   variations called Telecommunications Devices for the Deaf (TDDs) are
   used by the hearing impaired for typed communications over ordinary
   telephone lines.
   [ ]

Contents

     * 1 History
     * 2 Ways in which teleprinters were used
     * 3 Teleprinter operation
          + 3.1 Control characters
          + 3.2 Answer back mechanism
     * 4 Manufacturers
          + 4.1 Creed & Company
          + 4.2 Gretag
          + 4.3 Kleinschmidt Labs
          + 4.4 Morkrum
          + 4.5 Olivetti
          + 4.6 Siemens & Halske
          + 4.7 Teletype Corporation
          + 4.8 Texas Instruments
     * 5 Telex
     * 6 Teletypesetter
     * 7 Teleprinters in computing
     * 8 Obsolescence of teleprinters
     * 9 See also
     * 10 References
     * 11 Further reading
     * 12 External links
          + 12.1 Patents

History[edit]

   The teleprinter evolved through a series of inventions by a number of
   engineers, including Samuel Morse, Alexander Bain, Royal Earl House,
   David Edward Hughes, Emile Baudot, Donald Murray, Charles L. Krum,
   Edward Kleinschmidt and Frederick G. Creed. Teleprinters were invented
   in order to send and receive messages without the need for operators
   trained in the use of Morse code. A system of two teleprinters, with
   one operator trained to use a keyboard, replaced two trained Morse code
   operators. The teleprinter system improved message speed and delivery
   time, making it possible for messages to be flashed across a country
   with little manual intervention.^[4]

   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.^[5] 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.^[6] 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.^[7]

   By 1846, the Morse telegraph service was operational between
   Washington, D.C., and New York. Royal Earl House patented his printing
   telegraph that same year. He linked two 28-key piano-style keyboards by
   wire. Each piano key represented a letter of the alphabet and when
   pressed caused the corresponding letter to print at the receiving end.
   A "shift" key gave each main key two optional values. A 56-character
   typewheel at the sending end was synchronised to coincide with a
   similar wheel at the receiving end. If the key corresponding to a
   particular character was pressed at the home station, it actuated the
   typewheel at the distant station just as the same character moved into
   the printing position, in a way similar to the (much later) daisy wheel
   printer. It was thus an example of a synchronous data transmission
   system. House's equipment could transmit around 40 instantly readable
   words per minute, but was difficult to manufacture in bulk. The printer
   could copy and print out up to 2,000 words per hour. This invention was
   first put in operation and exhibited at the Mechanics Institute in New
   York in 1844.

   Landline teleprinter operations began in 1849, when a circuit was put
   in service between Philadelphia and New York City.^[8]
   Hughes telegraph, an early (1855) teleprinter built by Siemens and
   Halske. The centrifugal governor to achieve synchronicity with the
   other end can be seen.

   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.^[9]

   In France, Emile 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.^[10]

   During 1901, Baudot's code was modified by Donald Murray (1865-1945,
   originally from New Zealand), prompted by his development of a
   typewriter-like keyboard. The Murray system employed an intermediate
   step, a keyboard perforator, which allowed an operator to punch a paper
   tape, and a tape transmitter for sending the message from the punched
   tape. At the receiving end of the line, a printing mechanism would
   print on a paper tape, and/or a reperforator could be used to make a
   perforated copy of the message.^[11] As there was no longer a direct
   correlation between the operator's hand movement and the bits
   transmitted, there was no concern about arranging the code to minimize
   operator fatigue, and instead Murray designed the code to minimize wear
   on the machinery, assigning the code combinations with the fewest
   punched holes to the most frequently used characters. The Murray code
   also introduced what became known as "format effectors" or "control
   characters" - the CR (Carriage Return) and LF (Line Feed) codes. A few
   of Baudot's codes moved to the positions where they have stayed ever
   since: the NULL or BLANK and the DEL code. NULL/BLANK was used as an
   idle code for when no messages were being sent.^[4]

   In the United States in 1902, electrical engineer Frank Pearne
   approached Joy Morton, head of Morton Salt, seeking a sponsor for
   research into the practicalities of developing a printing telegraph
   system. Joy Morton needed to determine whether this was worthwhile and
   so consulted mechanical engineer Charles L. Krum, who was vice
   president of the Western Cold Storage Company. Krum was interested in
   helping Pearne, so space was set up in a laboratory in the attic of
   Western Cold Storage. Frank Pearne lost interest in the project after a
   year and left to get involved in teaching. Krum was prepared to
   continue Pearne's work, and in August, 1903 a patent was filed for a
   'typebar page printer'.^[12] In 1904, Krum filed a patent for a 'type
   wheel printing telegraph machine'^[13] which was 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
   synchronizing method for code telegraph systems, which made possible
   the practical teleprinter.^[14]

   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.^[15]^[16]

   In 1916, Edward Kleinschmidt filed a patent application for a typebar
   page printer.^[17] In 1919, shortly after the Morkrum company obtained
   their patent for a start-stop synchronizing method for code telegraph
   systems, which made possible the practical teleprinter, Kleinschmidt
   filed an application titled "Method of and Apparatus for Operating
   Printing Telegraphs"^[18] which included an improved start-stop
   method.^[19] The basic start-stop procedure, however, is much older
   than the Kleinschmidt and Morkrum inventions. It was already proposed
   by D'Arlincourt in 1870.^[20]
   Siemens t37h (1933) without cover

   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. The new company combined the
   best features of both their machines into a new typewheel printer for
   which Kleinschmidt, Howard Krum, and Sterling Morton jointly obtained a
   patent.^[19]

   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 Bureau of Lighthouses,
   Airways Division, Flight Service Station Airway Radio Stations system
   in 1928, carrying administrative messages, flight information and
   weather reports.^[21] By 1938, the teleprinter network, handling
   weather traffic, extended over 20,000 miles, covering all 48 states
   except Maine, New Hampshire, and South Dakota.^[22]

Ways in which teleprinters were used[edit]

   There were at least five major types of teleprinter networks:
     * Exchange systems such as Telex and TWX created a real-time circuit
       between two machines, so that anything typed on one machine
       appeared at the other end immediately. US and UK systems had
       telephone dials, and prior to 1981 five North American Numbering
       Plan (NANPA) 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 tape and 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.
     * Message switching systems were an early form of E-mail, using
       electromechanical equipment. See Telegram, Western Union, Plan
       55-A. Military organizations had similar but separate systems, such
       as Autodin.
     * Broadcast systems such as weather information distribution and
       "news wires", which were received on "wire machines".^[23] Examples
       were operated by Associated Press, National Weather Service,
       Reuters, and United Press (later 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.^[24]

Teleprinter operation[edit]

   Keyboard of a Baudot teleprinter, with 32 keys, including the space bar
   International Telegraph Alphabet 2 development of the Baudot-Murray
   code

   Most teleprinters used the 5-bit International Telegraph Alphabet No. 2
   (ITA2). This limited the character set to 32 codes (2^5 = 32). One had
   to use a "FIGS" (for "figures") shift key to type numbers and special
   characters. Special versions of teleprinters had FIGS characters for
   specific applications, such as weather symbols for weather reports.
   Print quality was poor by modern standards. The ITA2 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. (Early systems had used synchronous codes, but were hard
   to synchronize mechanically). Other codes, such as FIELDATA and
   Flexowriter, were introduced but never became as popular as ITA2.

   Mark and space are terms describing logic levels in teleprinter
   circuits. The native mode of communication for a teleprinter is a
   simple series DC circuit that is interrupted, much as a rotary dial
   interrupts a telephone signal. The marking condition is when the
   circuit is closed (current is flowing), the spacing condition is when
   the circuit is open (no current is flowing). The "idle" condition of
   the circuit is a continuous marking state, with the start of a
   character signalled by a "start bit", which is always a space.
   Following the start bit, the character is represented by a fixed number
   of bits, such as 5 bits in the ITA2 code, each either a mark or a space
   to denote the specific character or machine function. After the
   character's bits, the sending machine sends one or more stop bits. The
   stop bits are marking, so as to be distinct from the subsequent start
   bit. If the sender has nothing more to send, the line simply remains in
   the marking state (as if a continuing series of stop bits) until a
   later space denotes the start of the next character. The time between
   characters need not be an integral multiple of a bit time, but it must
   be at least the minimum number of stop bits required by the receiving
   machine.

   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 common
   carrier and consisted of ordinary telephone cables that extended from
   the teleprinter located at the customer location to the common carrier
   central office. These teleprinter circuits were connected to switching
   equipment at the central office for Telex and TWX service. Private line
   teleprinter circuits were not directly connected to switching
   equipment. Instead, these private line circuits were connected to
   network hubs and repeaters configured to provide point to point or
   point to multipoint service. More than two teleprinters could be
   connected to the same wire circuit by means of a current loop.

   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.^[25] 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.^[26] 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, such as the assassination of
   John F. Kennedy.

   The teleprinter circuit was often linked to a 5-bit paper tape punch
   (or "reperforator") and reader, allowing messages received to be resent
   on another circuit. 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 code 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 saved in machine-readable form and
   edited off-line.

   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[edit]

   Main article: Control character

   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 (carriage return), advance to the same
   column of the next line (line feed), and so on. Commands to control
   non-printing operations were transmitted in exactly the same way as
   printable characters by sending control characters with defined
   functions (e.g., the line feed character forced the carriage to move to
   the same position on the next line) to teleprinters. In modern
   computing and communications a few control characters, such as carriage
   return and line feed, have retained their original functions (although
   they are often implemented in software rather than activating
   electromechanical mechanisms to move a physical printer carriage) but
   many others are no longer required and are used for other purposes.

Answer back mechanism[edit]

   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.^[27]^[28] 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[edit]

Creed & Company[edit]

   A Creed & Company Teleprinter No. 7 in 1930

   British Creed & Company built teleprinters for the GPO's teleprinter
   service.^[29]
     * 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[edit]

   The Gretag ETK-47 teleprinter developed in Switzerland by Edgar
   Gretener in 1947 uses a 14-bit start-stop transmission method similar
   to the 5-bit code used by other teleprinters. However, instead of a
   more-or-less arbitrary mapping between 5-bit codes and letters in the
   Latin alphabet, all characters (letters, digits, and punctuation)
   printed by the ETK are built from 14 basic elements on a print head,
   very similar to the 14 elements on a modern fourteen-segment display,
   each one selected independently by one of the 14 bits during
   transmission. Because it does not use a fixed character set, but
   instead builds up characters from smaller elements, the ETK printing
   element does not require modification to switch between Latin,
   Cyrillic, and Greek characters.^[30]^[31]^[32]^[33]

Kleinschmidt Labs[edit]

   In 1931, American inventor Edward Kleinschmidt formed Kleinschmidt Labs
   to pursue a different design of teleprinter. In 1944 Kleinschmidt
   demonstrated their lightweight unit to the Signal Corps and in 1949
   their design was adopted for the Army's portable needs. In 1956,
   Kleinschmidt Labs merged with Smith-Corona, which then merged with the
   Marchant Calculating Machine Co., forming the SCM Corporation. By 1979,
   the Kleinschmidt division was turning to Electronic Data Interchange
   and away from mechanical products.

   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[edit]

   Morkrum made their first commercial installation of a printing
   telegraph with the Postal Telegraph Company in Boston and New York in
   1910.^[34] It became popular with railroads, and the Associated Press
   adopted it in 1914 for their wire service.^[15]^[35] Morkrum merged
   with their competitor Kleinschmidt Electric Company to become
   Morkrum-Kleinschmidt Corporation shortly before being renamed the
   Teletype Corporation.^[36]^[37]

Olivetti[edit]

   Olivetti Teleprinter

   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[edit]

   Siemens Fernschreiber 100 teleprinter

   Siemens & Halske, later Siemens AG, a German company, founded in 1897.
     * Teleprinter Model 100 Ser 1 (end of the 1950s) - Used for Telex
       service^[36]
     * 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[edit]

   Main article: Teletype Corporation
   A Teletype Model 33 ASR teleprinter, with punched tape reader and
   punch, usable as a computer terminal

   The Teletype Corporation, a part of American Telephone and Telegraph
   Company's Western Electric manufacturing arm since 1930, was founded in
   1906 as the Morkrum Company. In 1925, a 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 the American Telephone and
   Telegraph Company and became a subsidiary of Western Electric. In 1984,
   the divestiture of the Bell System resulted in the Teletype name and
   logo being replaced by the AT&T name and logo, eventually resulting in
   the brand being extinguished.^[38] The last vestiges of what had been
   the Teletype Corporation ceased in 1990, bringing to a close the
   dedicated teleprinter business. Despite its long-lasting trademark
   status, the word Teletype went into common generic usage in the news
   and telecommunications industries. Records of the United States Patent
   and Trademark Office indicate the trademark has expired and is
   considered dead.^[39]

   Teletype machines tended to be large, heavy, and extremely robust,
   capable of running non-stop for months at a time if properly
   lubricated.^[40] 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
     * 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[edit]

   Main article: Silent 700

   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.^[41] 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[edit]

   A Teletype Model 32 ASR used for Telex service

   Main articles: Telex and Telegraphy S: 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[edit]

   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)^[42] used by news wire services. It was first demonstrated in
   1928 and began to see widespread use in the 1950s.^[43] 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").^[44]

   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.^[45]

   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 Syndicated columns, News agency news, Classified advertising,
   and more, to different publications across wide geographical areas.

   In later years the incoming 6-bit current loop signal carrying the TTS
   code was connected to a minicomputer or mainframe for storage, editing,
   and eventual feed to a phototypesetting machine.

Teleprinters in computing[edit]

   A Teletype Model 33 ASR with paper tape reader and punch, as used for
   early modem-based computing

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

   Users typed commands after a prompt character was printed. Printing was
   unidirectional; if the user wanted to delete what had been typed,
   further characters were printed to indicate that previous text had been
   cancelled. When video displays first became available the user
   interface was initially exactly the same as for an electromechanical
   printer; expensive and scarce video terminals could be used
   interchangeably with teleprinters. This was the origin of the text
   terminal and the command-line interface.

   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[edit]

   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, email, and the Internet.

   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.

   As a result, by the mid-1990s, amateur use of actual teleprinters had
   waned, though a core of "purists" still operate on equipment originally
   manufactured in the 1940s, 1950s, 1960s and 1970s.^[citation needed]

See also[edit]

     * Letter-quality printer
     * Plan 55-A, a message switching system for telegrams
     * Radioteletype
     * Siemens and Halske T52 - the Geheimfernschreiber (secrets
       teleprinter)

References[edit]

    1. ^ Roberts, Steven, Distant Writing
    2. ^ Nelson, R.A., History Of Teletype Development, archived from the
       original on November 5, 2020
    3. ^ Latifiyan, Pouya (Winter 2021). "Aeronautical Fixed
       Telecommunication network and surrounding technologies". Take off.
       Civil Aviation Technology College. 2.
    4. ^ ^a ^b "Typewriter May Soon Be Transmitter of Telegrams" (PDF),
       The New York Times, January 25, 1914
    5. ^ "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)."
    6. ^ Roberts, Steven. "3. Cooke and Wheatstone". Distant Writing: A
       History of the Telegraph Companies in Britain between 1838 and
       1868.
    7. ^ Steven Roberts. "Distant Writing - Bain".
    8. ^ RTTY Journal Vol. 25 No. 9, October 1977: 2.
    9. ^ "David Edward Hughes". Clarkson University. April 14, 2007.
       Archived from the original on April 22, 2008. Retrieved September
       29, 2010.
   10. ^ Hobbs, Alan G. "Five-unit codes". Retrieved May 1, 2012.
   11. ^ Foster, Maximilian (August 1901). "A Successful Printing
       Telegraph". The World's Work: A History of Our Time. Vol. II.
       pp. 1195-1199. Retrieved July 9, 2009.
   12. ^ "U.S. Patent 888,335 issued in May, 1908". Retrieved July 14,
       2019.
   13. ^ "U.S. Patent 862,402". Retrieved July 14, 2019.
   14. ^ "U.S. Patent 1,286,351 filed in May, 1910, and issued in
       December, 1918". Retrieved July 14, 2019.
   15. ^ ^a ^b Colin Hempstead, William E. Worthington (2005).
       Encyclopedia of 20th Century Technology. p. 605.
       ISBN 9781579584641.
   16. ^ "Morkum Printing Telegraph Page Printer". Retrieved August 15,
       2011.
   17. ^ KLEINSCHMIDT, E. (April 14, 1916). "TELEGRAPH PRINTER". USPO.
       Retrieved July 11, 2008.
   18. ^ KLEINSCHMIDT, E. (May 1, 1919). "METHOD OF AND APPARATUS FOR
       OPERATING PRINTING TELEGRAPHS". USPO. Retrieved July 11, 2008.
   19. ^ ^a ^b Huurdeman, Anton A. (2003). The Worldwide History of
       Telecommunications. Wiley-IEEE. p. 302. ISBN 0-471-20505-2.
   20. ^ Deckert, Juergen; Koesling, Heinz (1987). Fernschreibtechnik
       [Teletype Technology] (in German). Berlin: Militaerverlag der
       Deutschen Demokratischen Republik (VEB). ISBN 3-327-00307-6.
   21. ^ "Flight Service History 1920-1998".
   22. ^ "FAA HISTORICAL CHRONOLOGY, 1926-1996" (PDF).
   23. ^ "AP teletype machine". CBC History. Retrieved March 5, 2022.
   24. ^ "Signaling system". March 29, 1944. Retrieved February 7, 2019.
   25. ^ "Introduction to RTTY" (PDF). Sam's Telecomms Documents
       Repository.
   26. ^ "RTTY Demodulators".
   27. ^ "ASR 33 Teletype Rear View of Main Assembly".
   28. ^ "Teletype Model 32ASR".
   29. ^ Baudot.net: Creed & Company, Ltd.
   30. ^ "Gretag ETK-47 14-bit teleprinter system".
   31. ^ "ETK teletype equipment series".
   32. ^ F. Doerenberg. "Other manufacturers of teleprinter machines that
       use the Hellschreiber principle". Section "Dr. Edgar Gretener AG
       (Gretag)".
   33. ^ "The Hagelin - Gretener Cipher Teleprinter".
   34. ^ Colin Hempstead, William E. Worthington (2005). Encyclopedia of
       20th-century technology. p. 605. ISBN 9781579584641.
   35. ^ "Morkum Printing Telegraph Page Printer". Retrieved August 22,
       2011.
   36. ^ ^a ^b "Queensland Telecommunications Museum - Teleprinters".
       Queensland Telecommunications Museum.
   37. ^ Earle, Ralph H. (1917). The Morkrum System of Printing
       Telegraphy. Chicago: Armour Institute of Technology (thesis).
   38. ^ "History of The Teletype Corporation". Archived from the original
       on June 3, 2008. Retrieved March 3, 2010.
   39. ^ Trademarks. "Search trademark database".
   40. ^ Adjustments, Type Bar Page Printer, (Model 15) (PDF). Chicago:
       Teletype Corporation. 1941. Archived from the original (PDF) on
       January 11, 2011.
   41. ^ "Old Vintage Computing Research: Refurb weekend: Texas
       Instruments Silent 700 Model 745 teletype". February 17, 2022.
   42. ^ The History of Printing and Printing Processes, retrieved 2008
       July 15
   43. ^ W. David Sloan, Lisa Mullikin Parcell, ed. (April 10, 2002).
       American Journalism: History, Principles, Practices. McFarland.
       p. 365. ISBN 978-0-7864-1371-3.
   44. ^ Mergenthaler Linotype Company (1951). The Linotype Handbook for
       Teletypesetter Operation. Dr. David M. MacMillan. digital reprint
       by www.CircuitousRoot.com.
   45. ^ Doug Kerr. "Teletypes in Typesetting". Glendale, Arizona, USA:
       Southwest Museum of Engineering, Communications and Computation.
       Retrieved April 25, 2017.

Further reading[edit]

     * "Teletype Messages Sent Through Switch Board", Popular Mechanics,
       April 1932. AT&T offering two way service through switchboards
     *

   A.G. Hobbs, G8GOJ; E.W. Yeomanson, G3IIR; A.C. Gee, G2UK (1983).
   Teleprinter handbook (2nd ed.). RSGB. ISBN 0-900612-59-2.

     Foster, Maximilian (September 1901). "A Successful Printing
   Telegraph". The World's Work. Vol. II, no. 5. New York, NY: Doubleday,
   Page & Co. pp. 1195-1200. Retrieved April 29, 2012.

     Gannon, Paul (2006). Colossus: Bletchley Park's Greatest Secret.
   London. ISBN 978-1843543312. on the role of the teleprinter code in
   WWII

External links[edit]

   Wikimedia Commons has media related to Teleprinter.

     * A first-hand report of Teletype Corporation's early years
     * 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[edit]

     * U.S. Patent 1,665,594 "Telegraph printer" (Type 12 Teletype), filed
       June 1924, issued April 1928
     * U.S. Patent 1,745,633 "Telegraph receiver" (Type 14 Teletype),
       filed December 1924, issued February 1930
     * U.S. Patent 1,904,164 "Signalling system and apparatus therefor"
       (Type 15 Teletype) - filed July 1930, issued April 1933
     * U.S. Patent 3,507,997 "Frequency-Shift Teletypewriter" - filed
       August 1966, issued April 1970

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