Video disc player with variable offset RFI reduction circuit

Claim 1

In a video disc player of the type having: pickup apparatus for recovering an information signal recorded on a disc in the form of a modulated carrier signal; demodulation apparatus; defect detection apparatus for detecting defects in the recovered signal; and defect compensation apparatus responsive to the operation of the defect detection apparatus for providing a substitute signal in place of the recovered signal in the playback display of said information signals during occurrences of defects in the recovered signal; said player being subject to interference with normal playback display operations due to the pickup of unrecorded, externally applied signals; apparatus for reducing the influence of said external signals comprising: an amplifier responsive to the signal provided by said pickup apparatus; a signal detector for detecting amplitude variations in the amplifier output signal; first and second conductive paths coupled to an output terminal of said detector, said first path being responsive to a wide band of frequencies, said second path being responsive to a relatively low band of frequencies, one of said paths having a means for providing a variable d.c. offset, said offset varying as a function of said detected amplitude variations; said means for providing a variable d.c. offset comprising: an integrator circuit responsive the output of said detector; a transistor having a base electrode coupled to said integrator circuit, a collector electrode coupled to one end of a load resistor and an emitter electrode coupled to a point of reference potential; the other end of said load resistor being coupled to an output terminal of said signal detector; and said collector electrode being connected to said first conductive path; a voltage comparator coupled to said first and second paths for providing an output signal in response to a detected signal having an amplitude greater than said offset voltage and a frequency higher than said low band of frequencies; and means coupling said comparator output signal to said defect compensation apparatus.