Abstract: Excessive peak beam currents conducted by a kinescope in a color television receiver are limited by apparatus which compares the combined instantaneous magnitudes of plural color signals with a fixed threshold and, if exceeding the threshold, the combined signal is detected. The detected signal is used to limit the magnitudes of the color signals, thereby limiting excessive kinescope beam currents otherwise developed in response to the color signals. The apparatus is used in the receiver together with a more conventional automatic kinescope beam current limiter of the type which operates in conjunction with a kinescope resupply current source.

Abstract: A kinescope driver amplifier includes a signal gain determining feedback network coupled from the output to the input of the amplifier. A normally non-conductive switching network coupled to the feedback network is rendered conductive in response to large amplitude video signals for modifying the impedance of the feedback network so as to reduce the signal gain of the amplifier during the occurence of such large video signals.

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 source of variable DC gain control voltage for a gain controllable video display system including an image display kinescope comprises a manually adjustable potentiometer, and a variable conduction ambient light sensing device located in proximity to the kinescope display screen. A gain control voltage provided at an output terminal of the source normally varies both manually as a function of the potentiometer setting, and automatically as a function of varying conduction of the light sensing device in response to varying ambient light levels. Automatic gain control provided by the light sensing device is defeated when the potentiometer is set to an extreme position corresponding to maximum gain, so that maximum signal gain (i.e., maximum image contrast) can be produced in low ambient light conditions.

Abstract: In the luminance channel of a color TV receiver, a horizontal peaking signal representative of the difference between delayed and undelayed luminance signals is subject to coring, with the level of coring subject to variation. Residual peaking signal remaining after core cancellation, is subject to gain controlled signal translation, and then combined with luminance signal to form peaked luminance signal. Frequency selective amplifier, responsive to peaked luminance signal, supplies its output to peak detector. Control voltage developed by peak detector adjusts gain of peaking signal translator in sense opposing amplitude variations of detector input, providing compensatory gain variations when coring level changes affect residual peaking signal amplitude.

Abstract: In a system for enhancing horizontal detail of a luminance signal, a horizontal peaking signal to be added to the luminance signal is cored with the depth of coring varied in accordance with a coring control potential. To develop the coring control potential, the input luminance signal is capacitively coupled to the input of a signal translator comprising an inverting amplifier with a frequency selective negative feedback path providing the translator with a low pass characteristic and a signal delay substantially equal to the delay of a delay line employed in peaking signal formation. An additional feedback path is provided by the emitter-collector path of a clamping transistor that conducts in response to sync pulse appearances to readjust the charge on the input capacitor, clamping the sync pulse peaks to a potential selected to establish a desired coring depth for black scene regions. Amplifier gain is set to provide translator output swing establishing a desired minimum coring depth (e.g.

Abstract: A color television receiver circuit arrangement is disclosed for facilitating the on-screen kinescope display of alphanumeric information. The receiver includes plural video output kinescope driver stages, a source of black-level reference bias voltage to which video signals amplified by the kinescope driver stages are normally referenced, and a source of control signals representative of the alphanumeric information. During picture intervals when alphanumeric information is to be displayed on a given area of the kinescope screen, the normal video signal and video driver outputs are blanked, and the control signal is employed to modify the kinescope driver black level reference bias voltage in a white level direction. The modified reference bias is sufficient to unblank the video driver outputs so that the kinescope is caused to conduct a white level signal corresponding to the alphanumeric information, which is then displayed by the kinescope.

Abstract: A circuit for automatically controlling the high frequency peaking content of an image representative video signal processed in the luminance signal path of a television receiver is disclosed. The luminance path also includes a linear phase network for generating a peaking signal which is added to the video signal for accentuating high frequency video signal components. The control circuit forms a closed feedback loop with the peaking network. The control circuit develops a control voltage in response to the high frequency content of the video signal, including peaking components already present in the video signal and as imparted from the peaking network. The control voltage controls the level of the locally generated peaking component to maintain the overall peaking content of the video signal within desired limits.

Abstract: A circuit for peaking video signals is disclosed. The circuit includes a differential amplifier which produces a peaking component at an output, and a signal delay line for determining the frequency at which maximum peaking occurs. The delay line input is coupled to a source of video signals to be peaked and to one input of the differential amplifier, and the delay line output is coupled to another input of the differential amplifier and to a signal combining point. A peaked video signal is produced by combining the peaking component from the differential amplifier with the delayed signal from the delay line. The operating parameters of the peaking circuit are established with respect to a normally expected range of video signal amplitude transitions so that the differential amplifier exhibits a linear response for transient or aperiodic transitions throughout the amplitude transition range.

Abstract: A circuit for generating a composite timing signal in a television receiver comprises a gate pulse generating circuit, and a voltage divider coupled across a fixed voltage source. The composite signal comprises a first pulse developed at an output of the voltage divider during television signal horizontal and vertical blanking intervals, and a second pulse developed by the gate pulse circuit during a portion of the horizontal and vertical blanking intervals and superimposed on the first pulse. A switching device coupled to the voltage divider responds to horizontal and vertical timing control signals applied via signal coupling circuits for enabling the voltage divider to develop the first pulse. The level of the first pulse is predictably determined by the voltage divider substantially independent of the amplitudes of the horizontal and vertical timing signals, and the values of circuit components included in the timing control signal coupling circuits.

Abstract: In a color television receiver luminance channel, transistor amplifier stage develops respective versions of input video signals across load resistors in collector and emitter circuits. Capacitor links collector to stage's output terminal, and parallel combination of inductor and resistor links emitter to output terminal. Parameter values are chosen to cause stage to provide delay-versus-frequency characteristic compensatory for delay distortion introduced by receiver's IF amplifier. Use of variable resistor as collector load resistor provides facility for adjustable peaking of luminance channel's amplitude-versus-frequency characteristic while maintaining delay distortion compensation effect.