| 摘要 |
PURPOSE:To rapidly detect a malfunction and automatically activate again by providing a means for detecting an existence of a video signal, a shift means, a malfunction detecting means and a means for generating a start pulse during energizing a power source and detecting the malfunction. CONSTITUTION:Video signal detectors 11-16 detect the existence of a video signal and comprise a synchronizing separator circuit and a monostable multivibrator. Shift register circuits 21-26 comprise negaters and logical product elements and latch elements and logical sum elements. A start pulse generator 30 comprises a power source on detecting circuit 31, logical product element 32, monostable multivibrators 33, 37, latch elements 34, 35 and a logical product element 36. A malfunction detector 60, when more then two outputs of the shift register circuits 21-26 operate or all the outputs do not operate, generates a malfunction detecting pulse (t) to reset the shift registers 21-26 and at the same time operate the start pulse generator.
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