Abstract: In a video display apparatus having a service mode of operation, a vertical deflection circuit includes a vertical deflection winding coupled to a DC blocking capacitor. An output stage includes first and second output amplifiers coupled to the vertical deflection winding in a push-pull arrangement at an output terminal. A vertical sawtooth voltage generator is coupled to a driver stage via an error amplifier that provides both AC and DC negative feedback for driving the output stage at a vertical rate in a sawtooth manner to generate a sawtooth deflection current in the deflection winding and for establishing a DC operating voltage level at the output terminal that charges the DC blocking capacitor. A service mode switching circuit is coupled to the driver stage for asserting the service mode of operation by maintaining the first output amplifier in cutoff and the second output amplifier in conduction to discharge the DC blocking capacitor and disable the generation of the sawtooth deflection current.

Abstract: Dual squelch circuits, the first preceding and the second following the video processor of a video disc player, are selectively activated by a control unit which receives transducer position information from the processor for calculation of disc playing time and control of the signal recovery transducer. The first squelch circuit aids in stabilizing the timebase correction servo of the video processor during the player pause operating mode. The second squelch circuit maintains video blanking during certain player transition operating modes (e.g., pause-to-play, load, etc.) while the control unit processes the position information to provide transducer control and playing time indicator signals.

Abstract: A bidirectional pulse generator for driving a video disc stylus deflector. Responsive to a deflection pulse a charge integrator has its input connected to a polarity selectable current source. The integrator generates a ramped potential output signal having an amplitude proportional to the deflection pulse width and a slope related to the current polarity. Upon termination of the deflection pulse a feedback loop is closed around the integrator to rapidly reset the output potential of the integrator to one of two pre-pulse output amplitudes. A direction control selects the current source polarity and controls the pre-pulse output amplitude and thereby the relative polarity of the output pulse.

Abstract: An oscillator including a resonator having a primary feedback loop for causing oscillations to occur at a desired frequency and a secondary feedback loop including a multiplier for causing variations of said frequency in response to an input signal manifestation. Spectral purity is enhanced and potential overtone oscillations are suppressed by a cascade connection of lag networks in the primary loop which exhibit a low-pass transfer characteristic and provide at least .pi. radians of phase shift, one of the networks being shared in common with the secondary loop for supplying a quadrature signal to the multiplier.

Abstract: A squelch circuit responsive to a squelch signal mutes audio and video circuits in a video disc player, preconditions a video signal correction servo system to the center of its control range and inhibits a defect correction circuit. A squelch memory, set by the simultaneous occurrence of the squelch signal and a loss of carrier signal derived from the output of the player pickup transducer, maintains the muting, preconditioning and inhibiting functions. When the squelch signal terminates the squelch memory is reset upon subsequent termination of the loss of carrier signal whereby the audio and video circuits are immediately unmuted, stabilization is rapidly established by the preconditioned video signal correction servo system and the defect correction circuit is primed.

Abstract: Periodic biasing of video disc player signal correction servo to the center of its control range avoids the loss-of-loop gain which otherwise could occur if the servo were continuously biased and minimizes loop stabilization time. Periodic biasing is provided by means of a timing circuit, responsive to a luminance signal transition above blanking level, which enables the servo phase error detector and simultaneously enables a precharging circuit which charges the servo error voltage holding capacitor to a level corresponding to a zero error servo condition. The timing circuit disables the precharging circuit a predetermined time subsequent to an opposite transition of the luminance signal and disables the phase detector subsequent to disabling of the precharging circuit.

Abstract: A first amplifier compares an input signal with the sum of a position control signal and a first width control signal and a second amplifier compares the position control signal with the sum of the input signal and a second width control signal, the second width control signal being derived from the same source as the first. Output circuitry combines unipolar output currents produced by the amplifiers to provide a net output current which flows in one sense to a load when the input signal is more positive than a first level and flows in the opposite sense when the input signal is more negative than a second level. No output current flows when the input signal lies within a dead zone defined by said levels, the position and width of the dead zone being separately and non-interactively controllable by said position and width signals.

Abstract: An active filter separates the function of a principal feedback loop which provides velocity error correction from that of a nested feedback loop which provides video signal frequency correction. A further feedback loop responsive to the active filter output signal and normally open under steady-state conditions, is closed under transient conditions for supplying a limited gain reducing signal to the input of the active filter whereby transient disturbance of the primary and nested loops is minimized with no loss of loop gain under steady-state conditions. The third loop includes a dead zone amplifier for distinguishing between transient and steady-state conditions and a limiter for limiting the gain reducing signal to a level below that which otherwise would tend to drive the active filter into a non-linear slow recovery condition.