IBM 740

Cathode ray tube output recorder


IBM 740 Cathode ray tube output recorder

IBM 740 Cathode ray tube output recorder

IBM 740 Cathode ray tube output recorder
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.

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.

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.

Renting for $2,850 a month, the IBM 740 also was used with the IBM 704 and IBM 709 Data Processing Systems. In the illustration above, the 740 (at right) is connected to the IBM 701 Electronic Analytical Control Unit (at left).