tailieunhanh - An Encyclopedia of the History of Technology part 75

An Encyclopedia of the History of Technology part 75. This one of a kind encyclopedia presents the entire field of technology from rudimentary agricultural tools to communication satellites in this first of its kind reference source. Following an introduction that discusses basic tools, devices, and mechanisms, the chapters are grouped into five parts that provide detailed information on materials, power and engineering, transportation, communication and calculation, and technology and society, revealing how different technologies have together evolved to produce enormous changes in the course of history | PART FOUR COMMUNICATION AND CALCULATION Figure Cylinder phonograph for recording and transcribing dictation the governor regulated the speed of the weight-driven motor . to record the singing voice. However until the commercial pressing industry began around 1900 multiple copies could only be made by using a bank of machines or copying from one machine to another. Magnetic and optical recording and reproduction Edison in 1878 and Tainter in 1885 had proposed magnetic recording but it was not until 1898 that Valdemar Poulsen invented a system for recording on a steel wire the telegraphone. One of the biggest advantages of a magnetic-recording medium was its erasability so that it could be used again and again particularly important in business applications such as dictating. Poulsen also suggested magnetically coated tapes and discs in his patents but exploitation of these media had to wait until plastics were discovered and a coating industry in place. In 1920 an Austrian Pfleumer developed a plastic magnetic tape but it was not until 1934 that magnetic recording tape was first manufactured by BASF in Germany. After the war largely due to the enthusiasm of Bing Crosby tape became the preferred medium for prerecording radio programmes. Tape became standard in recording studios soon afterwards. Another means of sound recording is optical and it would not have been surprising if Edison one of the inventors of the motion picture had hit upon this means of adding sound. In fact Edison s laboratory had been able to synchronize film and discs in 1889 and Joseph Poliakoff a Russian patented a 722 INFORMATION photoelectric system in 1900. Augustus Rosenberg patented a stereophonic talking film system in 1911. However none of these systems were commercialized. In 1926 Warner Brothers tried to stimulate lagging interest in its films by making synchronized-sound motion picture talkies . They chose to use a sound-ondisc system and contracts were awarded to Western Electric

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