Signal loss dectector for video disc

摘要

A video disc playback system includes a circuit for detecting degradation in signals recovered from a disc and generates a control pulse responsive to the detected degradation. The degradations are of a predetermined duration and represent a predetermined percentage decrease in amplitude. A peak detecting and following circuit is connected for receiving signals recovered from the disc record. The decay rate of the peak detecting circuit is arranged to be substantially equal to a certain minimum duration of amplitude degradations that should occur before it is desired to generate the control pulse. The output signal from the detector circuit is proportioned by a divider circuit and then integrated to produce a signal which is proportional to the average of the detected signal over a relatively long period of time. The proportioned signal is applied to the reference signal terminal of a comparator circuit and the detected signal is applied to the signal input terminal of the comparator. The comparator is conditioned to change states when the detected signal falls below the proportioned signal.