Abstract: A ferrite shield component for suppressing high frequency signals in electrical circuits, such as tuners for television receivers, is formed by surrounding an electrical conductor with ferrite material. The shield component is formed in the shape of a leadless chip to permit placement on a circuit board by chip insertion machines. The conductor pattern and ferrite material may be selected to determine particular impedance-frequency characteristics.

Abstract: A superheterodyne receiver having a plurality of selectable bands includes a tuning voltage source and a band selection signal source. To improve tracking, the receiver includes a selectively enabled voltage modifying arrangement responsive to the band selection signal for providing a modified tuning voltage to one of the radio frequency and local oscillator tuning circuits when the tuning voltage is within a predetermined portion of its range.

Abstract: In a superheterodyne receiver, such as a typical television receiver, a radio frequency coupling arrangement includes a first resonant circuit coupled to receive the input signal and further coupled to a second resonant circuit by a first coupling. Both resonant circuits are tuned to the desired signal frequency. The capacitive branch of the first resonant circuit includes a circuit impedance for providing a neutralizing voltage, at least a portion of which is coupled by a second coupling to the inductive branch of the second resonant circuit. The circuit impedance is selected to cause cancellation in the inductive branch between image frequency components coupled by the first coupling and image frequency components coupled by the second coupling, without substantially affecting the desired signals.

Abstract: A multiband local oscillator of a television tuner comprises a common collector transistor amplifier, a feedback circuit for conditioning the amplifier to oscillate in the wide range of frequencies for VHF broadcast and cable channels and a tuning circuit coupled to the base electrode of the transistor. Bandswitching signals are applied to switching diodes in the multiband tuning circuit to produce tuned circuit configurations for the various frequency bands. When one band is selected, the corresponding bandswitching signal is coupled to the switching diode associated with a lower band to turn it on as well as the switching diode for the selected band to inhibit out-of-band oscillators due to parasitic elements of the tuning circuit.

Abstract: An interstage coupling network is provided comprising a series connection of an even number of reactive elements coupled between the input and output terminals of the interstage network, a junction point of said series connection of inductors being coupled to a signal reference potential via a first reactive shunt element. A series connection of oppositely-poled switching diodes is coupled in parallel with a portion of said series connection of reactive elements, the junction between the series-coupled diodes being coupled to the signal reference potential via a second reactive shunt element. A third reactive element is coupled between the network output terminal and a point on the series connection of reactive elements which is remote from the input terminal of the network.

Abstract: In a color TV receiver incorporating automatic kinescope bias (AKB) control circuits, a first train of monolevel pulses with timing suitable for retrace blanking purposes and a second train of monolevel pulses with "backporch" timing appropriate for burst gating purposes are applied to a circuit serving to generate at a first terminal a train of bilevel pulses exhibiting a first voltage level during periods of overlapping of the pulses of the first and second trains, and exhibiting a second, lesser voltage level during the remaining, non-overlapping portions of the pulses of the first train. A resistor interconnects the first terminal with a second terminal. A keyed voltage source, responsive to a third train of monolevel pulses timed to indicate recurring kinescope bias control intervals, develops a voltage of a third level, intermediate the first and second voltage levels, at the second terminal during the recurring control intervals.

Abstract: A color TV receiver is provided with an encoding/decoding system for a trilevel sandcastle pulse train, exhibiting a middle pulse level during recurring kinescope bias control intervals, and comprising excursions between a base level, a low pulse level, and a high pulse level during periods outside said kinescope bias control intervals. The system's decoder includes a trio of voltage comparators for comparing incoming sandcastle pulses with respective reference voltages derived from three different intermediate points on a common voltage divider connected across the terminals of a DC supply. The system's encoder includes keyed means for determining the middle pulse level of the trilevel sandcastle pulse train in accordance with the output of a second voltage divider connected across the same DC supply as the first voltage divider. An output of a third, selectively enabled, voltage divider, connected across the same DC supply as the first and second voltage dividers, is determinative of said low pulse level.

Abstract: A dynamic noise filter especially adapted for use in audio reproduction systems within a television display device is provided to eliminate perceived noise. An audio signal having a relatively wide frequency range is passed through a variable bandwidth lowpass filter, the upper frequency cutoff point being variable in response to a control signal. A control path includes a filter and detector circuit for generating the control signal in response to the amplitude of the audio signal within an upper frequency portion of the audio signal frequency range. The control signal controls the bandwidth of the lowpass filter inversely with respect to the level of the audio signal within the upper frequency portion of the frequency range. A further filter is included in the control path for providing substantial attenuation at the fundamental frequency and lower order harmonic frequencies of the television horizontal line scanning signal in order to prevent the control path from erroneously responding to this signal.

Abstract: In an automatic kinescope bias (AKB) control system, a signal with a magnitude representative of the black current level conducted by the kinescope of a television receiver is derived from a sense point. The derived signal is coupled via a signal path to a processing network including input clamping and sampling networks for developing a bias correction voltage. A source of auxiliary control signal, coupled to the signal path prior to the clamping network, is subject to being undesirably influenced by impedance variations manifested by the sense point. An impedance included in the signal path between the sense point and the auxiliary signal source compensates for the sense point impedance variations, and also increases the immunity of the clamping network to spurious signals including noise and locally generated interference.

Abstract: A television receiver includes a DC coupled video output amplifier for supplying video signals to the cathode of an image reproducing kinescope, and an automatic kinescope bias (AKB) control system for maintaining a desired cathode black image current level. A video processor supplies video signals to the output amplifier via an input network including a manually adjustable resistor for pre-setting the amplifier gain. During AKB operating intervals, a substantially zero voltage drop is maintained across the adjustable gain control resistor so that the setting of the adjustable gain control resistor desirably has no influence on the kinescope cathode bias voltage monitored by the AKB system.

Abstract: A pulse generator for a television receiver produces keying pulses during the video signal back porch interval in order to energize burst gate and brightness control circuitry. The pulse generator is triggered by horizontal sync pulses under strong, noise-free video signal conditions. As the quality of the video signal and the horizontal sync pulses deteriorate due to noise or a weakening signal, the pulse generator is triggered by horizontal retrace pulse in order to provide keying pulses under all video signal conditions.

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: A television receiver including a video signal sync separator and keyed signal processing circuits responsive to keying signals supplied by a keying signal generator is disclosed. The output of the sync separator is filtered to develop a bias voltage with a magnitude in accordance with the average output level of the sync separator. The keying signal generator provides periodically timed output keying signals in response to locally generated periodic horizontal flyback signals. The operation of the keying signal generator is enabled or disabled in response to the magnitude of the bias voltage derived from the sync separator output.

Abstract: An automatic kinescope beam current limiter for a television receiver includes a source of derived beam current representative voltage, a keyed sampling circuit for developing an output beam current control voltage on a charge storage capacitor in response to the derived voltage, and an auxiliary current path including an impedance coupled between the output capacitor and the source of derived voltage. In a normal beam limiting control mode, the control voltage from the sampling circuit serves to modify the television signal in response to the derived voltage in a direction to limit excessive beam current. In an abnormal control mode such as when the sampling circuit is inoperative due to disrupted keying, current is conducted via the auxiliary current path in response to the derived voltage to modify the control voltage on the capacitor with a sense and at a rate for limiting excessive beam current, to thereby preserve beam limiting capability.

Abstract: A video signal channel in a television receiver includes a keyed filter, followed by a keyed automatic brightness control circuit for establishing a desired black or blanking level for the video signal. The brightness control circuit operates during blanking intervals of the video signal to sense the blanking level of the video signal for deriving a control signal which is utilized to maintain a desired blanking level. The filter comprises a high-pass filter circuit which is decoupled for filtering purposes during image intervals, but is coupled to the video channel during the blanking intervals for suppressing high frequency signals including noise, when present, in the video channel during the blanking intervals. The sensed blanking level and the control voltage are therefore unaffected by noise components which would otherwise impair the control signal and thereby the operation of the brightness control circuit.