Abstract: A peaking circuit for use in a digital video signal processing system includes a digital peak detector which produces a peak magnitude whenever the slope of the video signal changes polarity. The peak magnitudes, and the absences of peaks are summed in an accumulator over a field period. The accumulated peaks are applied to a gain calculating circuit which develops a peaking control signal having three regimes. For low valued accumulated peaks the gain or peaking control signal is constant and relatively large. For high valued accumulated peaks the gain is constant and negative. In between the gain is in inverse porportion to the value of the accumulated peaks.

Abstract: In a color TV receiver, a first digital signal of "m" bits represents high frequency component of combed luminance signal, and a second digital signal of "m" bits represents combed chrominance component. The "k" most significant bits of the first signal (where "k" is less than "m") are fed to respective inputs of a first "or" gate, while the "j" most significant bits of the second signal (where "j" is less than, or equal to, "m") are fed to respective inputs of a second "or" gate. The "or" gate outputs are fed, without delay difference, to inputs of a first "and" gate, and are fed, with a delay difference of 90.degree. at color subcarrier frequency, to inputs of a second "and" gate. Sequence recognition apparatus, responsive to the outputs of both "and" gates, develops a correlation indication in response to existence of predetermined sequences of outputs from one or both "and" gates.

Abstract: Control signal generator is responsive to the output of a pair of correlation indicators. One correlation indicator provides an indication of the presence or absence of correlation between high frequency components derived without difference in delay from the respective luminance and chrominance outputs of a color TV receiver's comb filter system. The other correlation indicator provides an indication of the presence or absence of correlation between high frequency components derived with a difference in delay from the respective comb filter outputs, the delay difference corresponding to a quarter period at the nominal color subcarrier frequency. Control signal is developed in response to a correlation indication by either or both of the indicators. The luminance output of the comb filter is subjected to high frequency component removal during control signal development.

Abstract: In a color TV receiver, a color AFPC loop, responsive to line rate synchronizing bursts of subcarrier frequency derived from the output of a first of a pair of cascaded chrominance signal amplifiers, controls the frequency and phase of an output of a VCO. The VCO output is passed through a variable phase shifter external to the AFPC loop to develop reference oscillations for use by color demodulators. Control of the variable phase shifter is effected by the output of a phase detector which compares the phases of (a) an output of the variable phase shifter and (b) line rate synchronizing bursts derived from an output of the second chrominance signal amplifier.

Abstract: A TV receiver arranged to process video signals in PCM binary format includes a manual hue control circuit which operates on the PCM color mixture signals to effectively rotate the vector sum of the color mixture signals while maintaining the magnitude of the sum substantially constant. The magnitude of the received vector sum is calculated and the angle between the sum and one of the color mixture signal components is determined. Circuitry under user control increments or decrements the angle to rotate the vector sum. Corrected color mixture signals are then generated by multiplying the magnitude of the calculated vector sum by the sine and cosine of the incremented angle.

Abstract: Trilevel sandcastle pulse decoder includes a trio of voltage comparators for comparing incoming sandcastle pulses with reference potentials of respectively different levels. One of the voltage comparators, which is subject to change in operating state in response to appearance of a given level of the sandcastle pulse, is precluded from operating state change in response to the appearance of the next higher level of the sandcastle pulse by control circuitry responsive to the output of a second of the voltage comparators. One of the decoder outputs is developed by logic circuitry responsive to outputs of two of the comparators.

Abstract: Quadrature-related outputs of synchronized color reference oscillator at +(R-Y) and +(B-Y) phases are applied to a first matrix to develop a first matrixed signal of a third intermediate phase. Additional matrixing operations on the oscillator outputs develop second and third matrixed signals of different phases symmetrically disposed about the third phase. A differential amplifier, of substantially fixed gain, with differential inputs respectively responsive to the second and third matrixed signals, develops a fourth matrixed signal, with a phase in quadrature relation with said third phase, across an output load. The reference signal input for a demodulator is derived from signals appearing across said output load.

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: A protection circuit is coupled between a low voltage signal processing semiconductor device subject to damage by high voltage transients, and a signal output terminal at which high voltage transients can appear. The protection circuit comprises a first transistor arranged as an emitter follower for normally conducting signals from the semiconductor device to the output terminal, and a second transistor of opposite conductivity type. The base and emitter electrodes of the first transistor are directly connected to the base and emitter electrodes of the second transistor, respectively, such that the second transistor is normally non-conductive. Transient currents associated with negative high voltage transients at the output terminal are diverted to a point of operating potential via the first transistor. The second transistor is rendered conductive in response to positive high voltage transients at the output terminal for diverting associated transient currents to a point of operating potential.

Abstract: A television receiver includes a character generator for permitting kinescope display of auxiliary characters in addition to display of normal video signal information, and means for sensing a given characteristic (e.g., bias) of video signal processing circuits of the receiver during prescribed sensing intervals. The character generator is disabled during the sensing intervals to prevent false outputs from the character generator from distorting the characteristic being sensed.

Abstract: A circuit for linearly controlling the gain of a differential amplifier includes a differentially connected current splitter network biased by means of a symmetrical bias circuit coupled to a common operating potential and including first and second current sources with associated first and second impedances. The current splitter includes a diode exhibiting a non-linear voltage in response to linear current conduction, and a transistor. The bias circuit responds to a variable gain control voltage for causing the diode to conduct current which varies linearly with the gain control voltage. First and second mutually differential control voltages derived from the transistor and diode, including a non-linearly varying voltage exhibited by the diode, are applied to the differential amplifier for controlling the conduction of the differential amplifier linearly with respect to the original control voltage.

Abstract: An image brightness control circuit is included in a television receiver which also includes a video signal black level clamp comprising a charge storage capacitor. The clamp operates during video signal blanking intervals, between picture intervals, for establishing a video signal black reference level. A variable brightness control voltage is applied to the clamp-controlled video signal only during picture intervals of the video signal. Brightness control is thereby achieved without introducing a visible gradual change in the brightness of a reproduced image, which would otherwise be produced by the action of the clamp charging or discharging the storage capacitor.

Abstract: A DC coupled system for automatically controlling the high frequency peaking content of a video signal is disclosed. The system includes a DC coupled control path comprising a peak detector for developing a control voltage representative of the high frequency content of the video signal exclusive of video signal DC components, and is preceded by a video signal amplifier. A filter for shaping the frequency response of the control path is connected to the amplifier. A manually adjustable peaking control for controlling the DC bias of the amplifier is also connected to the amplifier. The filter and adjustable peaking control exhibit mutually independent operation, and are both connected to the amplifier via the same single terminal.

Abstract: A DC coupled system for automatically controlling the high frequency peaking content of a video signal is disclosed. A peak detector develops a control voltage representative of the high frequency content of the video signal. The control voltage controls a differential control input peaking signal splitter to provide controlled amounts of complementary phased peaking signals, which are differentially combined with complimentary phased video signals to produce a controllably peaked video signal. The differential control inputs of the peaking signal splitter receive balanced quiescent bias from symmetrical bias coupling networks, one of which includes the peak detector.

Abstract: A DC coupled system for automatically controlling the high frequency peaking content of a video signal is disclosed. The system includes a DC coupled control path comprising a peak detector for developing a control voltage representative of the high frequency content of the video signal exclusive of video signal DC components. The detector is preceded in the control path by a frequency selective network comprising an amplifier and a filter for shaping the frequency response of the control path such that high frequency video signal components exclusive of DC video signal components are passed to the peak detector. The frequency selective network comprises the cascode combination of a video signal amplifier transistor and a current source transistor which provides quiescent operating currents for the amplifier transistor. The filter is coupled to the junction of the amplifier and current source transistors, and includes a DC blocking network coupled between the junction and a point of reference potential.

Abstract: In a video signal processing system, an input capacitor AC couples video signals to a DC coupled video signal path, and to a DC coupled peaking signal path for generating a peaking component which is combined with video signals from the video path to develop a peaked video signal. A feedback control voltage for controlling the DC level of the video signal is stored by the input coupling capacitor, and is DC coupled to both the video path and the peaking path in a manner to reduce the likelihood of a DC offset error when the video signal and peaking component are combined. In an embodiment, the control voltage is coupled to the storage capacitor via a delay line included in the video path and which is coupled across the differential inputs of a differential amplifier with which the delay line coacts to generate the peaking component.

Abstract: A frequency selective signal translating circuit is disclosed for use in a color television receiver including an automatic flesh tone color correction network which provides a reference signal for color demodulators of the receiver. The circuit comprises an input bandpass filter for attenuating unwanted frequency components from the reference signal output of the correction network. The filter is followed by a phase shifter for shifting the phase of the filtered reference signal as required for proper demodulator operation. The filter comprises a fixed alignment, single-tuned, series resonant circuit coupled in series between the correction network output and the demodulator reference signal inputs.