Formally announced on October 12, 1954, the 740 CRT output recorder was an electronic device attached to the IBM 701 Data Processing System. It provided output which recorded data points on the faces of a pair of television-like tubes at the rate of 8,000 per second. The larger tube, used for visual display and inspection, was a 21-inch tube. The smaller tube, used in conjunction with a camera, was a 7-inch tube. A customer-furnished camera was controlled by the 701 and automatically photographed information directed by the program.
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The 740 allowed decision making and possible intervention by the operator as the computation progressed. The device provided scientists and engineers with greater speed and accuracy in designing many types of equipment. For example, the shape of a cam could be computed and the shape, together with successive positions of the cam, could be displayed on the 740 at electronic speeds, inspected and then photographed for a permanent record. By using appropriate programming techniques, the 740 also could be used to display alphabetic characters, geometric shapes, engineering symbols and graphs. Traffic schedules or machine shop loadings, for example, could be shown on the 740, giving the operator the opportunity to monitor and incorporate data to facilitate the solution. This CRT Recorder was used with the IBM 701, IBM 704, and IBM 709 computers to draw vector graphics images on 35 mm photographic film (i.e. microfilm). The 740 film recorder contained digital to analog converters and a 7 inch, high precision, electrostatic CRT.
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| The console of the 701, at the General Electric Jet Engine Department, in 1954. IBM 701 Cathode Ray Tube (CRT) Display 8,300 points/sec. |
The raster size was 1024 by 1024, but only 256 resolved spots could be displayed on an axis line. The CRT used a short persistence P11 phosphor. Film was stored in a magazine that could hold up to 100 feet and could be advanced under computer control. ASA 200 speed film was recommended. The recording unit had an accuracy of 0.1 percent and the display unit had a 3.0 percent accuracy. (0.1 percent means that if a point with the same coordinates were to be displayed twice, the successive spots would differ in position by not more than 0.1 percent of full scale.) The time consumed in displaying a particular point was approximately 125 microseconds. The recording unit had a persistence of several microseconds and the display unit had a persistence of approximately 20 seconds.
Later in 1956 Lawrence Livermore National Labs uses the new IBM 740/780 to create recordings of B&W Motion Pictures. The IBM 780 CRT Display was a monitor that could be attached to the 740 and mirror to an operator what was being drawn on IBM 740 CRT. The 780 had a 21 inch CRT with a long persistence (2 second, nominal) P7 phosphor. |
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