Ateleprinter (teletypewriter,teletype orTTY) is anelectromechanical device used to send and receive typed messages through various communications channels, in bothpoint-to-point andpoint-to-multipoint configurations.
Initially, from 1887 at the earliest, teleprinters were used intelegraphy.[1]Electrical telegraphy had been developed decades earlier in the late 1830s and 1840s,[2] then using simplerMorse key equipment andtelegraph operators. The introduction of teleprinters automated much of this work and eventually largely replacedskilled operators versed inMorse code withtypists and machines communicating faster viaBaudot code.
With the development of earlycomputers in the 1950s,[3] teleprinters were adapted to allow typed data to be sent to a computer, and responses printed. Some teleprinter models could also be used to createpunched tape fordata storage (either from typed input or from data received from a remote source) and to read back such tape for local printing or transmission. A teleprinter attached to amodem could also communicate throughtelephone lines. This latter configuration was often used to connect teleprinters to remote computers, particularly intime-sharing environments.
Teleprinters have largely been replaced by fully electroniccomputer terminals which typically have acomputer monitor instead of a printer (though the term "TTY" is still occasionally used to refer to them, such as inUnix systems). Teleprinters are still widely used in the aviation industry (seeAFTN andairline teletype system),[4] and variants calledTelecommunications Devices for the Deaf (TDDs) are used by thehearing impaired for typed communications over ordinary telephone lines.
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The teleprinter evolved through a series of inventions by a number of engineers, includingSamuel Morse,Alexander Bain,Royal Earl House,David Edward Hughes,Emile Baudot,Donald Murray,Charles L. Krum,Edward Kleinschmidt andFrederick 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.[5]
There were a number of parallel developments on both sides of the Atlantic Ocean. In 1835Samuel Morse devised a recording telegraph, andMorse code was born.[6] Morse's instrument used a current to displace the armature of an electromagnet, which moved a marker, therefore recording the breaks in the current. Cooke & Wheatstone received a British patent covering telegraphy in 1837 and a second one in 1840 which described a type-printing telegraph with steel type fixed at the tips of petals of a rotating brass daisy-wheel, struck by an "electric hammer" to print Roman letters through carbon paper onto a moving paper tape.[7] In 1841Alexander 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 usingcentrifugal governors to closely regulate the speed of the clockwork. It was patented, along with other devices, on April 21, 1841.[8]
By 1846, theMorse telegraph service was operational between Washington, D.C., and New York.Royal Earl House patented hisprinting 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 theMechanics 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.[9]
In 1855,David Edward Hughes introduced an improved machine built on the work of Royal Earl House. In less than two years, a number of small telegraph companies, includingWestern Union in early stages of development, united to form one large corporation – Western Union Telegraph Co. – to carry on the business of telegraphy on the Hughes system.[10]
In France,Émile Baudot designed in 1874 a system using a five-unit code, which began to be used extensively in that country from 1877. The British Post Office adopted the Baudot system for use on a simplex circuit between London and Paris in 1897, and subsequently made considerable use of duplex Baudot systems on their Inland Telegraph Services.[11]
During 1901, Baudot's code was modified byDonald 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 apaper 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.[12] 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 mostfrequently used characters. The Murray code also introduced what became known as "format effectors" or "control characters" – theCR (Carriage Return) andLF (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.[5]
In the United States in 1902, electrical engineer Frank Pearne approachedJoy Morton, head ofMorton Salt, seeking a sponsor for research into the practicalities of developing aprinting telegraph system. Joy Morton needed to determine whether this was worthwhile and so consulted mechanical engineerCharles 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'.[13] In 1904, Krum filed a patent for a 'type wheel printing telegraph machine'[14] 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.[15]
In 1908, a working teleprinter was produced by the Morkrum Company (formed between Joy Morton and Charles Krum), called the Morkrum Printing Telegraph, which was field tested with the Alton Railroad. In 1910, the Morkrum Company designed and installed the first commercial teletypewriter system on Postal Telegraph Company lines between Boston and New York City using the "Blue Code Version" of the Morkrum Printing Telegraph.[16][17]
In 1916,Edward Kleinschmidt filed a patent application for a typebar page printer.[18] In 1919, shortly after theMorkrum 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"[19] which included an improved start-stop method.[20] The basic start-stop procedure, however, is much older than the Kleinschmidt and Morkrum inventions. It was already proposed by D'Arlincourt in 1870.[21]
Instead of wasting time and money in patent disputes on the start-stop method, Kleinschmidt and the Morkrum Company decided to merge and form theMorkrum-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.[20]
In 1924 Britain'sCreed & Company, founded byFrederick 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 theDaily 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 inlandTelex 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 theBureau of Lighthouses, Airways Division, Flight Service Station Airway Radio Stations system in 1928, carrying administrative messages, flight information and weather reports.[22] By 1938, the teleprinter network, handling weather traffic, extended over 20,000 miles, covering all 48 states except Maine, New Hampshire, and South Dakota.[23]
Teleprinters could use a variety of different communication channels. These included a simple pair of wires,public switched telephone networks, dedicated non-switched telephone circuits (leased lines),switched networks that operated similarly to the public telephone network (telex), and radio andmicrowave links (telex-on-radio, or TOR).
There were at least five major types of teleprinter networks:
Before thecomputer revolution (andinformation processing performance improvements thanks toMoore's law) made it possible to securely encrypt voice andvideo calls, teleprinters were long used in combination with electromechanical or electroniccryptographic devices to provide securecommunication channels. Being limited to text only was an acceptable trade-off for security.
Most teleprinters used the 5-bitInternational Telegraph Alphabet No. 2 (ITA2). This was limited to 32 codes (25 = 32), which was insufficient to encode all the alphabet as well as numbers and other characters. Therefore, the keyboard used the "FIGS" (for "figures") and "LTRS" (for "letters") keys to allow two encodingstates, with a total of 60 codes by sending one of two reserved characters to indicate the state of the following encoded stream (the letters were single case only). Special versions of teleprinters had FIGS characters for specific applications, such as weather symbols for weather reports. The ITA2 code was usedasynchronously 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 asFIELDATA andFlexowriter, were introduced but never became as popular as ITA2.
Mark andspace are terms describinglogic levels in teleprinter circuits. The native mode of communication for a teleprinter is a simple seriesDC circuit that is interrupted, much as arotary 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 (orASCII)null character.
Teleprinter circuits were generally leased from a communicationscommon carrier and consisted of ordinarytelephone cables that extended from the teleprinter located at the customer location to the common carriercentral office. These teleprinter circuits were connected to switching equipment at the central office forTelex andTWX service.Private line teleprinter circuits were not directly connected to switching equipment. Instead, these private line circuits were connected tonetwork hubs andrepeaters 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 acurrent 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 theTeletype 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 towords per minute, is the standard term introduced byWestern Union for a mechanical teleprinter data transmission rate using the 5-bit ITA2 code that was popular in the 1940s and 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.[27] This is true especially onhigh 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, orRayleigh fading can cause two carriers to randomly and independently fade to different depths.[28] 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 45.5baud (22.0ms per bit), a "66 speed" machine is geared at 50.0baud (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 thede facto standard foramateur radioRTTY operation because of the widespread availability of equipment at that speed and the U.S.Federal Communications Commission (FCC) restrictions to only 60 speed from 1953 to 1972. Telex,news agency wires and similar services commonly used 66 speed services. There was some migration to 75 and 100 speed as more reliable devices were introduced. However, the limitations of HF transmission such as excessive error rates due to multipath distortion and the nature of ionospheric propagation kept many users at 60 and 66 speed. Most audio recordings in existence today are of teleprinters operating at 60 words per minute, and mostly of the Teletype Model 15.
Another measure of the speed of a teletypewriter was in total "operations per minute (OPM)". For example, 60 speed was usually 368 OPM, 66 speed was 404 OPM, 75 speed was 460 OPM, and 100 speed was 600 OPM. Western Union Telexes were usually set at 390 OPM, with 7.0 total bits instead of the customary 7.42 bits.
Both wire-service and private teleprinters had bells to signal important incoming messages and could ring 24/7 while the power was turned on. For example, ringing 4 bells on UPI wire-service machines meant an "Urgent" message; 5 bells was a "Bulletin"; and 10 bells was a FLASH, used only for very important news.
The teleprinter circuit was often linked to a 5-bitpaper 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 editedoff-line.
Communication by radio, known asradioteletype orRTTY (pronouncedritty), 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.
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., theline 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.
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 anENQ (control E) signal, if enabled.[29][30] 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?"
BritishCreed & Company built teleprinters for theGPO's teleprinter service.[31]
The Gretag ETK-47 teleprinter developed in Switzerland byEdgar Gretener in 1947 uses a 14-bitstart-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 theLatin 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 modernfourteen-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.[32][33][34][35]
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 withSmith-Corona, which then merged with theMarchant 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 made their first commercial installation of a printing telegraph with the Postal Telegraph Company in Boston and New York in 1910.[36] It became popular with railroads, and theAssociated Press adopted it in 1914 for theirwire service.[16][37] Morkrum merged with their competitor Kleinschmidt Electric Company to become Morkrum-Kleinschmidt Corporation shortly before being renamed the Teletype Corporation.[38][39]
Italian office equipment makerOlivetti (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.
Siemens & Halske, laterSiemens, a German company, founded in 1847.
TheTeletype Corporation, a part ofAmerican Telephone and Telegraph Company'sWestern 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 theAmerican Telephone and Telegraph Company and became a subsidiary ofWestern 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.[40] 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 wordTeletype 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.[41]
Teletype machines tended to be large, heavy, and extremely robust, capable of running non-stop for months at a time if properly lubricated.[42] 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.
Several different high-speed printers like the "Ink-tronic" etc.
Texas Instruments developed its own line of teletypes in 1971, theSilent 700. Their name came from the use of athermal printer head to emit copy, making them substantially quieter than contemporary teletypes usingimpact 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 withacoustic couplers and some had internal storage, initiallycassette tape in the 1973 Models 732/733 ASR and laterbubble memory in the 1977 Models 763/765, the first and one of the few commercial products to use the technology.[44] In these units their storage capability essentially acted as a form ofpunched tape. The last Silent 700 was the 1987 700/1200 BPS, which was sold into the early 1990s.
A global teleprinter network calledTelex 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 usingBell 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, usingclass of service to preventPOTS 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 theInternet as most countries have discontinued telex/TWX services.
In addition to the 5-bit Baudot code and the much later seven-bit ASCII code, there was a six-bit code known as the Teletypesetter code (TTS) used by news wire services. It was first demonstrated in 1928 and began to see widespread use in the 1950s.[45] 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").[46]
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 aLinotype 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.[47]
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 assyndicated 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 aminicomputer ormainframe for storage, editing, and eventual feed to a phototypesetting machine.
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 interactivetime-sharingterminals until videodisplays became widely available in the late 1970s.
Users typed commands after aprompt 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 thetext terminal and thecommand-line interface.
Paper tape was sometimes used to prepare input for the computer session off line and to capture computer output. The popularTeletype Model 33 used 7-bitASCII code (with an eighthparity bit) instead of Baudot. The commonmodem communications settings,Start/Stop Bits andParity, stem from the Teletype era.
In early operating systems such asDigital'sRT-11, serial communication lines were often connected to teleprinters and were given device names starting withtt. This and similar conventions were adopted by many other operating systems.Unix andUnix-likeoperating systems use theprefixtty, for example/dev/tty13, orpty (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 externalconsole device, a user dialing into the system on amodem on aserial port device, a printing or graphicalcomputer terminal on a computer's serial port or theRS-232 port on aUSB-to-RS-232 converter attached to a computer's USB port, or even aterminal emulator application in the window system using apseudoterminal device.
Teleprinters were also used to record fault printout and other information in someTXE telephone exchanges.
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 thefax, 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 includingBaudot. 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.
In 1954 at MIT, researchers [began] experimenting with direct keyboard input to computers. Until then, computer users fed their programs into a computer using punched cards or paper tape. Douglas Ross… believed… aFlexowriter [teletypewriter]… could function as a keyboard input device… Thus in 1955 MIT'sWhirlwind [became] the first computer in the world to allow its users to enter commands through a keyboard…
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).
AT&T offering two way service through switchboards
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