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Browse Prior Art Database

CRT Protection and Analog Check System

IP.com Disclosure Number: IPCOM000095030D
Original Publication Date: 1965-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Cobb, RO: AUTHOR

Abstract

In a constant time cathode ray tube display system, the time allotted to generate a vector is controlled by a timer. This blanks the beam after the allotted time to prevent phosphor damage. To prevent damage resulting from counter failure, photomultiplier 11 is used to monitor the display on the screen of cathode ray tube 13. The output of photomultiplier 11 is applied to And 15.

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CRT Protection and Analog Check System

In a constant time cathode ray tube display system, the time allotted to generate a vector is controlled by a timer. This blanks the beam after the allotted time to prevent phosphor damage. To prevent damage resulting from counter failure, photomultiplier 11 is used to monitor the display on the screen of cathode ray tube 13. The output of photomultiplier 11 is applied to And 15.

A negative single-shot multivibrator 17, having a period equal to the constant time allotted for display, is applied to the second input or And 15. When the allotted time is up, the output from single- shot 17 becomes positive. If the beam is still unblanked as indicated by an output from photomultiplier 1 1, an output is applied through Or 19 to control grid 21 of cathode ray tube 13 to blank the CRT beam. Alternatively, the output of photomultiplier 11 is applied to Exclusive-Or 23, where it is logically combined with an unblank signal on line 25.

If photomultiplier 11 is down but an unblank command is given, or conversely, if an output is present on the cathode ray tube but an unblank signal is not given, an error condition exists. The error indication is applied to logical And 27. This provides an output on the next timing pulse from pulse generator TPG 29 through Or 19 to control grid 21 to blank the CRT beam.

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