Originally posted by DS23
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Although many believe that personal computer did not appear until the mid 1970's, there were a number of electromechanical devices prior to that aimed at hobbyists and capable of performing digital computations. The first of these was the Simon Mechanical Brain which was described by inventor Edmund Berkeley in his 1949 book "Giant Brains, or Machines That Think." Plans to build the Simon were published in a series of Radio-Electronics articles in 1950 and 1951. Development of electromechanical computers continued into the 1960's. The Minivac 601 was a model introduced in 1961 with its name derived from the Sperry Rand Univac computer.How fortunate for governments that the people they administer don't thinkComment
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By 1906, because of the work of Lee de Forest, inventors knew the two basic functions of a vacuum tube -- converting alternating current to direct current and amplifying an electronic signal. Over the decades, vacuum tubes were improved and were used in more and more complicated circuitry. At the 1939 World's Fair, for example, vacuum tubes were showcased in fully electronic television. And by 1945, the high-speed computer ENIAC was built, containing more than 17,000 tubes. Although successful, ENIAC and its offspring showed the real limitations of vacuum tubes: to make more powerful computers, more tubes would be needed, but at some point available space and energy would prevent further growth. Vacuum tubes were bulky, used a lot of energy, and were somewhat fragile and easy to overheat. Engineers knew they needed to find something different.How fortunate for governments that the people they administer don't thinkComment
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The telephone company had problems with vacuum tubes, too, and hoped to find something else to use for switching telephone calls. The idea of somehow using semiconductors (solid materials such as silicon that conduct electricity, but not as well as a conductor such as copper) had been tossed about before World War II, but knowledge about how they worked was scant, and manufacturing semiconductors was difficult. In 1945, however, the vice president for research at Bell Labs established a research group to look into it. The group was led by William Shockley and included Walter Brattain, John Bardeen, and others, physicists who had worked with quantum theory, especially in solids.How fortunate for governments that the people they administer don't thinkComment
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The team was talented and worked well together. After two years of frustrating but very exciting work, Bardeen and Brattain created an amplifying circuit that seemed to work, using the element germanium They called it the point-contact transistor. Its discovery was announced at a news conference, but received for the most part as a smart gizmo the phone company had developed. But in 1951, Shockley improved upon the original idea with a junction transistor. The importance of this small item gradually sank in. The transistor was a solid (thus the term "solid-state technology") but had the electrical properties of a vacuum tube. Yet it had none of the drawbacks: it was cheap, sturdy, used little power, worked instantly, and best of all, was tiny. Bell began to license the use of transistors (for a royalty) and offered courses on transistor technology, helping spread the word throughout the industry.How fortunate for governments that the people they administer don't thinkComment
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The first transistor available to consumers was in hearing aids, followed quickly by transistor radios. The computer industry immediately began designing computers using transistors that were faster, smaller, more economical, and more powerful.How fortunate for governments that the people they administer don't thinkComment
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* Avoid working on a player plugged into an AC outlet unless you are a qualified electronics technician.
* Follow the guidelines concerning electrostatic discharge whenever working on the electronic circuits in a player.
* Practice good soldering techniques with a soldering iron suitable for electronics work. If you lack soldering experience, gain it by assembling at least one electronic project kit prior to attempting to solder on a CED player circuit board.
* Own and study the service manual for the player you are working on. Many of these are obtainable from Sams Technical Publishing.
* Pay particular attention to the safety and servicing precautions printed in the front of the service manual.
* Read the general FAQs available at the Sci.Electronics.Repair Web Site. The FAQ Troubleshooting and Repair of Consumer Electronics Equipment is a good one to start with.How fortunate for governments that the people they administer don't thinkComment
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Originally posted by Troll View Posthe M25 is not a continuous loop. To the east of London, the toll crossing of the Thames between Thurrock and Dartford is the non-motorway A282. The Dartford Crossing, which consists of two tunnels and the QE2 (Queen Elizabeth II) bridge, is named Canterbury Way. Passage across the bridge or through the tunnels is subject to a toll, dependent upon the type of vehicle. Designating this stretch as a motorway would mean that traffic not permitted to use motorways could not cross the Thames east of Woolwich.The
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