Abstract: Color reference oscillator in a color television receiver comprises a non-inverting amplifier, with positive feedback from its output conveyed via a crystal filter to its input. A quadrature phase shift network, coupled to the filter output, develops phase shifted signals which are matrixed with signals derived directly from the non-inverting amplifier to form resultant signals with a phase intermediate the phases of the matrix inputs. Control voltage outputs of a phase comparator, responsive to oscillator signals and to received synchronizing bursts, determine the magnitude and polarity of the output of a controlled amplifier which has at its input the resultant signals produced by said matrixing. The controlled amplifier output, and the output of an inverting amplifier also responsive to said resultant signals, share the load resistor of the non-inverting amplifier.

Abstract: Color reference oscillator comprises a non-inverting amplifier, with positive feedback via a crystal filter linking its output and input. A quadrature phase shift network, coupled to the filter output, delivers phase shifted signals to a pair of independently controlled amplifiers. One of the controlled amplifiers is responsive to control voltage outputs of a burst-responsive phase detector so as to inject phase shifted signals into the oscillator loop, as and when required, to effect synchronization of oscillator with burst component of incoming color television signal. The second of the controlled amplifiers is responsive to a reference DC voltage and to a manually adjustable DC control voltage, and develops a phase shifted signal output, of a magnitude and polarity dependent upon the magnitude and sense of the difference, if any, between the respective DC voltages, for combination with the non-inverting amplifier's output.

Abstract: A pair of differential amplifier stages are connected in cascade to form a multistage amplifier for signal amplification purposes. The base-emitter paths of current source transistors which establish the operating currents for the respective stages are connected in series across a common source of forward bias voltage. The collector-emitter path of an additional transistor is shunted across the base-emitter path of one of the current source transistors. As biasing of the additional transistor is varied, the distribution of gain between the respective cascaded stages is altered substantially without disturbance of the overall gain of the multistage amplifier.

Abstract: Signals to be cored are applied to the inputs of a linear signal amplifier, and of a multistage limiting amplifier having cascaded input and output amplifying stages. A cored version of the signals, corresponding to the difference between a linearly translated version of the signals and a doubly clipped version thereof, is developed by a signal combiner responsive to the outputs of both amplifiers. A variable coring level control voltage controls the distribution of gain between the input and output amplifying stages, substantially without disturbing the overall gain of the limiting amplifier, which is set to match the overall gain of the linear amplifier. In an illustrative embodiment, the signals which are adjustably cored are horizontal peaking signals derived from the received luminance signal in a color television receiver. An automatic peaking control system associated with output of the adjustable coring circuit opposes changes in peaking level that might otherwise accompany coring level adjustment.

Abstract: Adjustable coring circuit includes linear amplifier and multistage limiting amplifier responsive to input signals from a common source. Limiting amplifier includes an input stage receiving operating current from a first current source transistor, in cascade with an output stage receiving operating current from a second current source transistor. Cored signal, corresponding to the difference between a linearly translated version of the input signals and a doubly clipped version thereof, is developed by a signal combiner responsive to outputs of both amplifiers. Base-emitter paths of the two current source transistors are connected in series across a common bias source. The base electrodes of two control transistors, of mutually opposite conductivity types, respond to variations of common coring level control voltage. Collector-emitter path of one control transistor shunts base-emitter path of first current source transistor.

Abstract: Dual-standard (PAL/SECAM) color TV receiver includes circuitry for automatically controlling the receiver's operating mode in accordance with recognition of the SECAM or PAL format of the received signals. A first sample-and-hold circuit monitors the output of an FM detector responsive to the received signals during blanking "backporch" portions of alternate line intervals, while a second sample-and-hold circuit monitors the output of said FM detector during blanking "backporch" portions of the intervening line intervals. Comparison of the outputs of the two sample-and-hold circuits achieves the desired format recognition. To avoid false recognition, sampling interval beginning is delayed relative to beginning of SECAM lead-in oscillations or PAL swinging bursts, while sampling interval termination substantially coincides with end of blanking interval.

Abstract: In a television receiver, a horizontal peaking signal is formed for addition to a luminance signal to enhance its horizontal detail by relatively boosting high frequency components of the luminance signal. The peaking signal is subject to a coring action with the depth of coring subject to dynamic control in accordance with level variations of low frequency content of the luminance signals. The sense of control is such that a greater coring depth is associated with dark portions of a scene to be reproduced than is associated with bright portions thereof.

Abstract: The composite video signal input to the voltage comparator of a TV receiver AGC system is subjected to the filtering action of a low pass filter for noise suppression purposes. A wideband signal path, bypassing the low pass filter, is enabled during trailing edges of noise impulses exceeding the normal sync peak level, in order to substantially preclude delay of the fall of said trailing edges.

Abstract: First 1-H type comb filter provides an output representative of the sum of current line video signals and preceding line video signals, which is delivered to an adder via a wideband signal path, as a wideband combed luminance signal input occupying a given band of frequencies. Second 1-H type comb filter provides an output representative of the difference between current line video signals and preceding line video signals which is delivered to said adder, via a signal path with a pass band restricted to only a low frequency portion of the given band, as a restricted band vertical detail signal input.

Abstract: In color TV receiver for SECAM-encoded signals, a single FM detector, subject to line-by-line switching of its center frequency tuning, achieves sequential demodulation of respective SECAM subcarriers. For the purpose of using an identification system of the type shown in U.S. Pat. No. 4,240,102, center frequency tuning at the R-Y subcarrier resting frequency is held throughout R-Y line interval and during lead-in burst of B-Y line interval, terminating at beginning of image portion of B-Y line interval. Transient signal component, associated with switching to B-Y subcarrier resting frequency at beginning of that image portion, is stretched into early segment of image portion by de-emphasis circuit following FM detector.

Abstract: Television receiver employs a synchronous video detector system, and includes an AFT detector responsive to carrier waves supplied by reference amplifier of synchronous detector system. A peak detector, independent of the synchronous video detector and the receiver's automatic gain control system, is responsive to the output of the receiver's IF amplifier, and supplies an output to a voltage comparator. When the comparison indicates the IF output swing exceeds a threshold value, the AFT detector is disabled to avoid an AFT "lockout" condition.

Abstract: A gain-controlled amplifier is provided, including first and second common emitter-coupled amplifying transistors for receiving differential input signals. The emitter circuits of the amplifying transistors include first and second controlled resistance devices, having base electrodes coupled to each other and to a source of gain-control potential, collector electrodes coupled to a source of reference potential, and respective emitter electrodes coupled to respective emitter electrodes of the amplifying transistors. Each of the controlled resistance devices includes a region of high resistivity (intrinsic) semiconductor material between the base and emitter electrodes, which gives the base-to-emitter junction of the device a PIN diode-like characteristic. The application of a gain-control potential to the bases of the devices may be used to vary both the small base-to-emitter current and the relatively larger emitter-to-collector current in the devices.

Abstract: A frequency selective chrominance signal translating circuit for use in a color television receiver employing a comb filter is disclosed. The comb filter responds to switching signals for providing separate outputs from which the luminance and chrominance television signal components are derived. The translating circuit includes first and second cascaded, bandpass filters tuned to frequencies above the chrominance subcarrier frequency. The first filter receives comb filter output signals including desired chrominance signals and undesired components at the frequency of the comb filter switching signal.

Abstract: Dual-mode control signal generator, responding to alternative forms of mode selection signal input by generating different arrays of control signal outputs, includes a trio of voltage comparators. In first form, mode selection signal consists of pulse train with DC component of such a magnitude that all signal excursions remain above a reference potential; in second form, DC component magnitude is such that all signal excursions remain below reference potential. In first comparator, comparison of signal with reference potential switches unvarying control current between output current paths in dependence upon form of control signal. In second comparator, comparison of level shifted signal with reference potential results in a pulse train output, but only in presence of first form of selection signal. In third comparator, comparison of oppositely level shifted signal with reference potential results in development of complementary pulse train outputs in presence of second form of selection signal.

Abstract: Sync-positive and sync-negative video signals appearing across load resistors of synchronous video detector employing array of NPN transistors are coupled via respective voltage dividers to complementary inputs of differential amplifier employing NPN transistors. Signals appearing across load resistor of amplifier are coupled via an active filter to video signal output terminal. Detector load circuits, amplifier load circuit, and active filter each provide high frequency roll off with break point lying between desired video passband and second subharmonic of picture carrier intermediate frequency. Active filter provides response boost within high end of video passband, and response null in vicinity of picture carrier intermediate frequency. Level shift circuit utilizes series resistance of active filter. Differential amplifier has current source responsive to amplifier output to avoid cut off of amplifier transistor receiving sync-negative drive.

Abstract: A power output circuit is provided which is protected against latching due to voltage pulses developed by an inductive load. The circuit comprises a transistor constructed on a monolithic integrated circuit chip including a grounded semiconductor substrate of one type conductivity, and including collector and emitter regions of opposite type conductivity located on the substrate and containing opposite type conductivity modifiers. The collector and emitter regions are separated by a base region of one type conductivity, and the collector region is coupled to the inductive load. A fourth region of one type conductivity, containing one type conductivity modifiers is located on the substrate in galvanic contact with the collector region. A resistive impedance is coupled between the fourth region and a source of reference potential, and a capacitor is coupled between the fourth region and the source of reference potential.

Abstract: Dual standard TV receiver includes means for identifying field frequency of received TV signals. A switching system responsive to output of field frequency identifying means alters circuitry of receiver's vertical deflection system in a manner maintaining same picture height for received signals of differing field frequencies. Circuitry alteration additionally effects appropriate alteration of free-running frequency of oscillator.

Abstract: A correction apparatus for a deflection yoke for use with a color television kinescope comprises a plurality of magnetically permeable rods disposed at the rear of the yoke. Each of the rods comprises a short portion disposed parallel to the neck of the kinescope and an elongated portion disposed perpendicular to the neck of the kinescope. The elongated portions of the rods are positioned within the external field of the vertical deflection coils. Flux from the external field is channeled into the rods to form a magnetic field between the short portions of corresponding members on opposite sides of the tube neck to provide vertical coma correction. The vertical dimension of the rods is a small fraction of the diameter of the kinescope neck in order that the high permeable path presented to the external horizontal field by the rods does not appreciably distort the external horizontal field.

Abstract: A self-converging deflection yoke having toroidally-wound vertical deflection coils incorporates a pair of magnetically permeable field formers mounted on either side of the yoke. The field formers shunt a portion of the external field flux to the vicinity of the electron gun assembly where they form a pincushion-shaped field which aids in vertical coma correction. In one embodiment, a yoke comprising planar-wound vertical coils incorporates both coma-correcting rear field formers and a pair of front crossarm assemblies for providing side-pincushion correction. The resultant yoke provides covergence of electron beams free of coma and side-pincushion distortion with reduced sensitivity to transverse motion. In another embodiment, similar results are obtained without the front crossarms by vertical deflection coil having a nonradial winding configuration.

Abstract: Color TV receiver subject to reception of SECAM signals incorporates dual-mode identification system for identifying and correcting an incorrect mode of line-by-line switching in SECAM demodulation apparatus. In one (horizontal) mode of operation, identification information is derived from lead-in bursts preceding image signals during active line intervals; in other (vertical) mode of operation, identification information is derived from identification oscillations present during selected line periods within vertical blanking interval. Single FM detector and pair of sample-and-hold circuits responsive to detector output are used in both modes of operation, with mode selection sensitive control signal generators developing detector center frequency tuning control, detector gain control, and sampling control waves of forms dependent on mode selected.