Abstract: A video sync validity detector comprises a peak detector circuit and an average detector circuit both responsive to output signals from a sync separator network. Sync representative signals are provided from the output of the peak detector. The average detector is coupled to the peak detector for inhibiting sync representative outputs therefrom in the presence of sync separator output signals representative of false sync signals of average value.

Abstract: As a signal seeking tuner tunes through a number of channels to locate the next active (useable) channel, the display screen of a television receiver is blanked when the receiver is tuned between channels or to an inactive (unuseable) channel for which video signal information is substantially absent. Superimposed over the blanked screen background is a moveable tuning indicator bar, the position of which indicates the channel to which the receiver is tuned. The blanking of the screen prevents the tuning indication from being obscured by background noise.

Abstract: A filter network suitable for processing a signal such as the demodulated "I" chrominance component of a composite color television signal is disclosed. The filter network comprises plural cascaded mutually interactive resonant LC sections for providing wideband filtering, amplitude peaking over a prescribed range of signal frequencies, and signal delay. Mismatched resistors terminate the filter network and constitute the primary DC impedance of the filter network, and the LC sections exhibit selected impedances at frequencies within the peaking frequency range.

Abstract: In a television receiver, a horizontal peaking signal is added to a luminance signal to accentuate its horizontal detail. The peaking signal is subject to a coring action with the amount of coring subject to dynamic control as a function of luminance signal content. The sense of coring control is such that a greater amount of coring is associated with dark portions of a scene to be reproduced than is associated with bright portions thereof. The coring control is non-linear and exhibits one control characteristic over a first range of luminance signal levels between a white image limit and a threshold level in the black image direction, and a different control characteristic over a second range of signal levels between the threshold level and the black image limit for restricting the amount of coring produced as the black limit is approached.

Abstract: A filter network suitable for translating a signal such as a demodulated "I" chrominance component of a composite color television signal is disclosed. The filter network comprises first and second cascaded sections with mutually grossly mismatched terminating impedances, and are passively interconnected via a resistance of a value which substantially precludes interaction between the sections over a given range of frequencies within the passband of the signals being translated. Both sections are separately excited with signals to be translated. The first section provides wideband filtering and a large amount of delay relative to that provided by the second section. The second section provides signal amplitude peaking within a given portion of the frequency passband of the first section.

Abstract: An input pulse having an amplitude to be sampled is coupled to a sampling amplifier via an input circuit including a capacitance. A switch couples a reference voltage to the capacitance during reference intervals preceding sampling intervals. The reference voltage is decoupled at the end of the reference interval, at which time an auxiliary reference pulse is self-generated at the amplifier input by passive circuit elements associated with the input circuit. The auxiliary pulse exhibits an amplitude and sense for negating the response of the amplifier to the input pulse when the input and reference pulses exhibit mutually equal amplitudes at the amplifier input.

Abstract: A coring circuit is provided in a system which includes a gain controlled device. The diodes which produce the coring effect are biased by a signal which is related to the gain control signal coupled to the device. In this way, the coring threshold is made to vary relative to changes in the amplitude of the applied signal so that the percentage of coring remains fixed over a range of applied signal amplitude levels.

Abstract: The contrast of an image reproduced by a television receiver is manually adjustable by means of a picture control potentiometer, and automatically adjustable by means of an ambient light responsive circuit. Automatic picture control is accomplished selectively, independent of the manual control setting, in accordance with a predetermined combination of ambient light and image brightness levels such that the contrast of bright images, rather than the contrast of all images, is automatically reduced in low ambient light. In a preferred embodiment such automatic picture control is accomplished by using the light responsive circuit to control the threshold operating level of an automatic kinescope beam current limiter of the receiver.

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 DC coupled signal translating circuit for supplying auxiliary graphics information switching signals to a video signal processor. The switching signal comprises plural switching levels including a quiescent level. The translating circuit includes first and second complementary conductivity input transistors with interconnected emitter signal inputs for receiving switching currents representative of the graphics switching signals via a conductor which undesirably exhibits a parasitic capacitance. The transistors are biased to conduct a nominal quiescent current and develop collector output currents which are proportional to the input switching currents, and which are respectively coupled via current repeating networks to control inputs of the video processor. Switching delays attributable to the parasitic capacitances of the input coupling conductor are significantly reduced due to the emitter voltage clamping action of the input transistors for all conditions of the input switching signals.

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: In a color television receiver including a comb filter for separating luminance and chrominance components of a color television signal, a network is included for selectively restoring, enhancing and paring vertical image detail to preserve and enhance vertical resolution in the luminance content of a displayed image. The comb filter provides a combed luminance signal output from which vertical detail signal information has been unavoidably deleted, and a combed chrominance signal output including signal frequency components representative of the deleted detail signal, which are selectively extracted from the combed chrominance signal. Low level detail signals are restored to the combed luminance signal via a first signal processing network which exhibits a prescribed signal restoration gain.

Abstract: A gain controllable circuit suitable for processing vertical detail signal information in a video signal is disclosed. The circuit exhibits a non-linear signal amplitude transfer function wherein different amounts of signal gain are imparted to signals having amplitudes within prescribed ranges. Small amplitude signals subject to restoration are translated with a prescribed restoration gain. Moderate amplitude signals subject to enhancement (peaking), and large amplitude signals subject to paring (amplitude reduction), are controllably amplified without altering the restoration gain characteristic for small signals.