Abstract: A SECAM-encoded chrominance signal is converted to a chrominance signal of a quasi-PAL form for further processing in PAL decoder apparatus. Converter includes an FM detector serving to demodulate respective SECAM subcarriers sequentially, and a modulator wherein the color-difference signals recovered by the FM detector amplitude modulate in appropriate sequence quadrature-related phases of PAL subcarrier frequency oscillations derived from the PAL decoder. The color-difference signals supplied to the modulator are augmented by line rate pedestals effecting the insertion of bursts in the quasi-PAL signal developed by the modulator. The phasing of the inserted bursts alternates between a first phase corresponding to the oscillation phase subject to modulation by R-Y color-difference signals, and a second phase differing from the first phase by 180.degree..

Abstract: SECAM subcarrier demodulator employs a multistage limiter-amplifier to supply two inputs to a signal multiplier, one input being supplied directly and the other input being supplied via a phase shifter which imparts a phase shift of 90.degree. at one of the SECAM subcarrier resting frequencies. Positive feedback is associated with the final amplifier stage of the limiter-amplifier to provide said stage with a hysteresis characteristic ensuring development of a limiter output with a rectangular waveshape having rise and fall times of substantial constancy, independent of input signal amplitude variations. Negative DC feedback from the penultimate amplifier stage to the input amplifier stage of the limiter-amplifier assures desired symmetry of limiting action. Color difference signal output is obtained by low pass filtering of the products of multiplication of the respective signal inputs.

Abstract: A system employed in a television receiver for decoding and displaying graphics information such as may be encoded on a broadcast video signal. The system includes a graphics signal decoder supplied with the encoded video signal, and a plurality of transmission gates responsive to logic control signals derived from outputs of the decoder. The gates are coupled to inputs of video output stages in the receiver, and operate in response to the control signals for interrupting normal video signals to the video output stages and for enabling a voltage representative of a graphics display intensity level to be coupled to the video output stages when graphics information is to be displayed.The system also includes a graphics level control network. The level control network limits excessive graphics representative beam current levels to prevent image defocusing and kinescope screen burn.

Abstract: A differential sample-and-hold circuit includes first and second emitter-coupled transistors the bases of which are coupled to the signal source to be sampled. A gated circuit source coupled to the joined emitters supplies operating current in the sampling mode and supplies no current in the holding mode. First and second rectifiers each serially coupled with a resistor are coupled between a reference voltage and the collectors of the first and second transistors, respectively. A hold capacitor is coupled between the collectors of the transistors.

Abstract: A peak detector circuit is provided for detecting the maximum excursions of an amplitude varying signal. The circuit includes a network comprising a capacitor serially coupled to a charging impedance and having a time constant suitable for responding to the maximum excursions of the amplitude varying signal. A semiconductor means has an input terminal for receiving the amplitude varying signal and an output terminal coupled to the charging impedance for charging the capacitor toward the maximum excursions of the amplitude varying signal. The semiconductor means exhibits an impedance which is subject to increase with a decrease in current drawn therethrough.

Abstract: A pickup stylus adapted for playing back prerecorded signals from a disc record groove of a given width upon establishment of stylus/record relative motion has a dielectric support element which has a tip. The terminating portion of the tip is shaped to have a prow, a substantially flat rear surface remote from the prow, a pair of substantially parallel side surfaces extending from the side edges of the rear surface, a bottom surface extending from the bottom edge of the rear surface and additional surfaces extending from the prow and intersecting the bottom and the side surfaces. The stylus tip is dimensioned such that the maximum separation between the substantially parallel side surfaces is less than the given width.

Abstract: The light power not occluded during a repetitive, transverse knife-edge scanning of a focused spot is measured by a photodetector while an interferometer measures the displacement of the knife-edge during the scanning operation. The knife-edge is supported on a glass plate carried by the photodetector with a liquid medium being located between the glass plate and the light sensitive surface of the photodetector to enhance light reception by the photodetector. The differentiated output of the photodetector when displayed (e.g., by means of an oscilloscope) provides a graphic representation of the intensity profile of the spot which is dependent on the composite refractive index of the glass plate and the liquid medium.

Abstract: A servo loop is provided in an optical record/play apparatus for controlling a motor assembly providing relative motion in a radial direction, with respect to a disc record, between the disc record and a beam of focused light. In a record mode of operation for the apparatus, the loop drives the motor at a rate providing a constant speed radial relative motion, as the disc record is rotated, to enable the inscription of a spiral information track on the disc. In a playback mode of operation for the apparatus, the loop drives the motor at a variable rate providing relative radial motion which assures the centering of the beam of focused light on a spiral information track formed in the disc record medium as the disc is rotated.

Abstract: Means are provided for detecting departures of the relative velocity between a signal pickup and the information track of a video disc from a predetermined value. Signals recovered when relative motion is established between the track of the disc and the signal pickup are subjected to a delay in a charge transfer delay line. The line delay is made to vary in response to the output of the detecting means so as to compensate for signal time base errors engendered through departures of said relative velocity from the predetermined value. Non-linearities of the time delay of the delay line with respect to the output of the detecting means, which are due to large changes in the output frequency of a voltage controlled oscillator utilized for controlling the operation of the delay line, are compensated for by means of a linearizing feedback loop for the oscillator.

Abstract: Apparatus provides an incident light beam which illuminates the surface of a resist coated grooved disc, having an exposure pattern of signal elements formed within the groove, with a light spot that spans a plurality of convolutions of the groove. As the resist coating is developed, portions of the resist coating corresponding to the exposure pattern are removed and the emerging structure of the signal elements serves as a diffraction grating which diffracts the incident light beam. Photodetector apparatus positioned to intercept a selected portion of the diffracted beam provides an output corresponding to the light power in the selected portion. Means responsive to the output of the photodetector are provided for directly indicating the achievement of a desired emerging signal element geometry in the region illuminated by the light spot to thereby control the resist development process.

Abstract: Improvement of the signal-to-noise ratio for a wideband video signal is effected by subtraction from the wideband video signal of a signal which follows low-amplitude excursions of the video signal's high frequency component. The latter signal is formed by a circuit arrangement which includes a high pass filter, of a C-R differentiator form, coupled to the input of an amplifier. A negative feedback path, coupled between the amplifier output and the junction of capacitive and resistive elements of the differentiator includes threshold devices which permit activation of the negative feedback path only during input signal excursions which exceed selected close-to-axis limits.

Abstract: In a system for playing back prerecorded signals from a spirally-grooved disc record by a groove-engaging signal pickup secured to a pickup arm when relative speed is established therebetween, a locked groove escape apparatus is provided. A transducer varies the position of the signal pickup in relation to the groove in a manner that opposes deviations of the relative speed from a predetermined speed. A carriage housing the pickup arm is mounted on the player base for movement between a playback mode and a standby mode. The carriage is driven radially inward in synchronization with rotation of the disc record during playback independent of radial motion of the signal pickup due to the spiral groove. A locked groove detector coupled to the transducer generates a locked groove recognition pulse when the signal pickup encounters a locked groove.