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A teleprinter (teletypewriter, Teletype or TTY) is an electromechanical typewriter that can be used to send and receive typed messages from point to point and point to multipoint over various types of communications channels. They 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 (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 Teleprinters have largely been replaced by fully electronic computer terminals which usually use a computer monitor instead of a printer (though the term "TTY" is still occasionally used to refer to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 (AFTN and airline teletype system), and variations called Telecommunications Devices for the Deaf (TDDs) are used by the hearing impaired for typed communications over ordinary telephone lines. ==History== The teleprinter evolved through a series of inventions by a number of engineers, including 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 typewriter, 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. 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 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.〔''RTTY Journal'' Vol. 25 No. 9, October 1977: 2.〕 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. appeared to carry on the business of telegraphy on the Hughes system. Émile Baudot designed a system using a five unit code in 1874. The Baudot system was adopted in France in 1877, and later extensively in France. 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. During 1901 Baudot's code was modified by Donald Murray (1865–1945), 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. 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.〔 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’.〔(【引用サイトリンク】 title=U.S. Patent 888,335 issued in May, 1908 )〕 In 1904, Krum filed a patent for a ‘type wheel printing telegraph machine’〔(【引用サイトリンク】 title=U.S. Patent 862,402 )〕 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.〔(【引用サイトリンク】 title=U.S. Patent 1,286,351 filed in May, 1910, and issued in December, 1918 )〕 In 1908, a working teleprinter was produced by the Morkrum Company, 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.〔(【引用サイトリンク】title=Morkum Printing Telegraph Page Printer )〕 In 1916, Edward Kleinschmidt filed a patent application for a typebar page printer. 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" which included an improved start-stop method. The basic start-stop procedure, however is much older than the Kleinschmidt and Morkrum inventions. It was already 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. 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.〔 In 1924 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 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. A Teletype system was installed in the Federal Aviation Administration Flight Service Station Airway Radio Stations system in 1928, carrying administrative messages, flight information and weather reports. By 1938, the FAA's Teletype network, handling weather traffic, extended over 20,000 miles, covering all 48 states except Maine, New Hampshire, and South Dakota. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Teleprinter」の詳細全文を読む スポンサード リンク
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