Abstract: Video disc player apparatus for aiding the signal recovery stylus to overcome locked grooves insurmountable by normal stylus deflection transducers. The player comprises a signal pickup stylus secured to a first end of a stylus arm, the second end thereof being secured to a carriage mechanism. The carriage mechanism is driven by a servomechanism responsive to the relative stylus-carriage position so as to translate the second end of the stylus arm in consonance with the radial travel of the pickup stylus engaging the disc. Secured within the carriage is a stylus deflection transducer which cooperates with the stylus arm to selectively translate the pickup stylus past a preselected number of grooves when the stylus is prevented from normal progression by a defect occurring on the disc surface. Occasionally defects occur which cannot be bypassed by deflector induced stylus translations due to limitations in the deflector transducer.

Abstract: A stylus position sensor for a video disc player apparatus. An electrode secured in fixed relation to a movable stylus is disposed between first and second electrodes to form first and second variable capacitors therewith. The capacitance of the variable capacitors change in accordance with the motion of the stylus related electrode between the first and second electrodes. A time varying signal is applied through fixed impedances to the first and second electrodes, the amplitude of the signal being modulated by voltage variable impedances connected between the first and second electrodes and a point of fixed potential. The modulated signals at said first and second electrodes are coupled to the stylus related electrode and the time average of the summed signal is indicative of the position of the stylus related electrode and thereby the stylus with respect to the first and second electrodes.

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 improved error code used for encoding and decoding data in a video disc system of the type wherein the data format comprises a start code followed by an error code and information bits. The error code is chosen so that the error code check register in the video disc player begins with the start code in the register, and, if no errors are detected after the full message is received, also ends with the start code in the register. This unique code simplifies both the control logic and the decoding logic in the video disc player decoder.

Abstract: Preemphasis and clipping apparatus is provided in a system for translating a signal wave from an input terminal to another terminal. The preemphasis and clipping circuits are arranged to interact with each other, as opposed to being isolated from one another, in a manner which tends to reduce distortions of the translated signal wave. The clipping circuit is arranged to change a time constant associated with the preemphasis circuit during the operation of the clipping action. The interaction also causes the clipping to be maintained beyond the time it would normally fall off.

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 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: 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: In a video disc player, a stylus arm, carrying a track-following stylus at one end thereof, has its other end secured to an arm cage by a compliant member. The arm cage is translated along a path disposed radially of the disc record during playback. Pickup circuits are employed for sensing the variations in a signal representative capacitance formed between an electrode incorporated in the pickup stylus and conductive material disposed in the record to recover prerecorded information from a spiral track disposed on the record. A stylus position indicative capacitance, established between a first electrode secured to the stylus arm and coupled to the pickup circuits and a second electrode mounted to the carriage in the vicinity of the first electrode, is modulated at a given frequency rate. Circuitry is provided for sensing signals at a given frequency appearing at the output of the pickup circuits to generate a signal indicative of the position of the pickup stylus relative to the arm cage.

Abstract: An integrator integrates the central portion of each signaling interval of a PCM input signal for a time less than the reciprocal of the PCM baud rate. Means responsive to the integrated signal or a manifestation thereof performs a comparison operation at the end of the integration period and stores the result until the end of the next following period. The integrator is reset between integration periods when transitions of the signal are likely to occur whereby immunity to PCM signal amplitude variations and transition edge distortion is enhanced and the probability that the integration will be monotonic is enhanced, thereby reducing the detector error rate.

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.

Abstract: In the playback of a video disc record employing an FM carrier recording format, a defect compensation system is provided which substitutes delayed video signals for current video signals when a defect is encountered. A phase locked loop including a phase detector and a voltage controlled oscillator is employed in FM detection circuits. A defect detector compares the phase between the oscillator output signal and a signal corresponding to the recovered signal. When the phase difference between these two signals exceeds a certain value, a defect signal is generated to disable the normal signal path of the recovered signal so that the delayed version of the video may be substituted for the current video for the duration of the occurrence of the defect.