Abstract: A dynamic focus amplifier, comprising: a first circuit responsive to a vertical rate sawtooth waveform for generating at the vertical rate a modulating waveform having a desired component of a given shape during trace intervals and an undesired time compressed version of the given shape during retrace intervals; a second circuit responsive to the sawtooth waveform for generating a pulse waveform at the vertical rate, substantially corresponding in width and phase to a vertical retrace blanking waveform; and, a differential amplifier stage, formed by Darlington pairs, for combining the modulating waveform and the pulse waveform to remove the undesired time compressed version of the given shape from the modulating waveform. The second circuit may comprise a capacitor which is charged in a first direction by the sawtooth waveform during vertical trace and charged in an opposite direction during vertical retrace.

Abstract: A screen grid voltage or a focus voltage for a cathode ray tube is controlled via a digital-to-analog converter. The voltage variation range of the screen grid or focus voltage that can be obtained for the entire variation range of an output signal of the digital-to-analog converter is not significantly larger than that required for the type of cathode ray tube that is utilized.

Abstract: A video display having raster correction comprises a cathode ray tube with a deflection coil mounted thereon for raster generation. A deflection amplifier is coupled to the deflection coil for generating a deflection current therein. A corrective waveform modulator is coupled to the deflection amplifier for generating a first corrective current in the deflection coil. An auxiliary coil is mounted on the cathode ray tube for raster correction. An auxiliary coil drive amplifier is coupled to the auxiliary coil for generating a second corrective current in the auxiliary coil. A first corrective signal is coupled to the waveform modulator for generating raster correction at a first raster edge and a second corrective signal is coupled to said auxiliary coil drive amplifier for generating raster correction at an edge opposite the first raster edge.

Abstract: A current transformer has a primary side winding coupled to a source of horizontal rate sawtooth yoke current and a secondary side in which a horizontal rate AC signal is developed. A rectifier has at least one capacitor, the rectifier receiving the horizontal rate AC signal and energizing a DC voltage across the at least one capacitor. A modulator for the DC voltage generates a first deflection rate waveform. A capacitor coupled to the modulator and to the secondary side of the transformer generates a second deflection rate waveform. The first and second deflection rate waveforms are combined to define a vertical dynamic focus voltage signal.

Abstract: In a horizontal deflection circuit output stage, a retrace pulse voltage is developed in a primary winding of a flyback transformer and transformer-coupled to a secondary winding and rectified for developing a high voltage. A portion of the transformer-coupled rectified voltage is combined in a voltage divider with a second rectified voltage. The second rectified voltage is produced in a peak rectifier from the retrace pulse voltage in the primary winding in a manner that bypasses the secondary winding. A screen grid voltage is developed at a terminal of the voltage divider. A change in beam current loading produces variations in opposite sense in the combined rectified voltages in a manner to regulate the screen grid voltage.

Abstract: An analog multiplier generates an output signal that is coupled to a convergence winding of a projection television. The analog multiplier multiplies a horizontal rate sawtooth signal with a vertical rate parabola signal. The multiplier DC operating point is adjusted, by developing a DC voltage in a hold capacitor of a sample and hold arrangement during each vertical blanking interval. To prevent a change in the capacitor voltage during vertical trace, a vertical rate sawtooth signal is coupled to the hold capacitor via a second capacitor.

Abstract: An analog multiplier is used for generating an output signal that is coupled to a convergence winding of a projection television. The analog multiplier multiplies a horizontal rate sawtooth signal with a vertical rate parabola signal. To prevent temperature related drift, tolerances and component aging from affecting the output signal, the multiplier is calibrated during each vertical blanking interval.

Abstract: A temperature compensated vertical rate trapezoidal waveform is produced using piecewise linearization technique. The waveform is applied to a focus electrode of a cathode ray tube to provide a dynamic focus voltage.

Abstract: Disclosed is an optical communication system which uses the self-pulsating frequency of a self-pulsating laser diode as a microwave subcarrier to transmit digital information. The system has a transmitter comprising a self-pulsating laser diode and a modulating mechanism for encoding the laser's self-pulsating microwave sub-carrier. In one embodiment, the modulating mechanism employs frequency-shift keying for digitally encoding the sub-carrier. Furthermore, the optical communication system has a receiver including a photodetector and a signal decoder.

Abstract: A source of switched supply voltage is applied to a potential divider and coupled to an output terminal via a capacitor. An output tap of the potential divider is coupled to the output terminal via the conduction path of a grounded base transistor. In operation the transistor (1) operates in an inverted mode for initially charging the capacitor, (2) operates in either a normal or an inverted mode for regulating a grid bias voltage at said output terminal for grid current flow of either direction relative to the output terminal and (3) operates in an isolation mode upon removal of the switched supply voltage whereby the capacitor applies a negative grid cut-off bias to the output terminal, said transistor in said isolation mode preventing discharge of the capacitor thereby providing a grid cut-off bias at said output terminal having an extended cut-off time constant due to the lack of any discharge path for the capacitor other than leakage.

Abstract: A circuit for protecting a cathode ray tube screen from damage by an electron beam includes a semiconductor switch device having an input coupled to a signal related to a deflection signal for the electron beam. The switch device is coupled to a voltage supply and the circuit further includes a charge storage device coupled to the switch device and further coupled to a control grid of the cathode ray tube. The charge storage device is charged through the switch device by the voltage supply when the deflection signal is present at a control input of the switch device. The switch device decouples the supply voltage from the charge storage device when the deflection signal is not present and places a negative blanking voltage developed on the charge storage device across the control grid when the deflection signal is not present to cut-off beam current in the cathode ray tube.

Abstract: A source of kine supply voltage is coupled to a video amplifier that drives a cathode of a cathode ray tube of a projection television receiver via a self biasing diode. When, due to, for example, a fault condition, the kine supply voltage is lost, the self biasing diode decouples the cathode of the cathode ray tube from a supply return terminal of an ultor supply voltage to form a high impedance, low capacitance at the cathode of the cathode ray tube. A beam current develops a self biasing voltage at the cathode of the cathode ray tube that substantially reduces the beam current to provide protection against a damage to a screen of the cathode ray tube.

Abstract: A television receiver includes a kinescope and a current sensing transistor for conveying amplified video signals to the kinescope, and for providing at a sensing output terminal an output signal related to the magnitude of kinescope current conducted during given sensing intervals. A clamping circuit clamps the sensing output terminal during normal image intervals, and unclamps the sensing output terminal during the sensing intervals. The clamping circuit facilitates interfacing the sensing transistor with utilization circuits which process the sensed output signal, and assists to maintain a proper operating condition for the sensing transistor.

Abstract: In a television receiver including a kinescope, a kinescope driver stage includes a video amplifier with an associated feedback path. A first emitter follower transistor couples amplified video signals from the amplifier output to the kinescope. A second emitter follower transistor, included in the feedback path for maintaining the continuity thereof, couples amplified video signals to the kinescope when a normally nonconductive diode coupled between the outputs of the emitter follower transistors is rendered conductive in the presence of large video signal amplitude transitions sufficient to render the first follower transistor nonconductive.

Abstract: In a wired remote control for use with a television receiver, audio signals are coupled to a loudspeaker by a transformer providing electrical isolation. The remote control device comprises an oscillator applying a signal at a frequency above the audio range to the transformer and a rectifier at the transformer secondary converting the oscillator signal to a DC signal. That DC signal is selectively applied by a switch to an optocoupler which couples to a control device for controlling the audio source. A filter blocks the oscillator signal from the speaker. Additionally, the control device controls TV channel selection.

Abstract: In a phase locked loop PLL tuning control system for a voltage controlled oscillator of the type wherein an automatic fine tuning (AFT) voltage is selectively applied to the local oscillator after a PLL configuration has obtained lock at the nominal frequency value for the selected channel so as to accommodate frequency translated RF carriers, an AFT control circuit selectively activated by the average level of composite synchronization pulses indicative of an improper tuning condition caused by certain translated carriers clamps the AFT voltage at a predetermined level. The predetermined level is selected to force the local oscillator frequency to be driven to an offset value at which an offset detector causes reinitiation of PLL control at discrete frequency step from the nominal value for the selected channel so as to properly tune the translated carrier.

Abstract: A television tuning system includes a memory for storing tuning information with first and second groups of memory locations for storing different tuning information for the same group of predetermined channels. A mode switch, in a first mode, allows memory locations in the first group to be addressed when channels in the predetermined group are selected and in a second mode allows memory locations in the second group to be addressed when channels in the predetermined group are selected. Such an arrangement is useful in a motel, hotel or hospital to allow certain channels in a list of channels to be selected when a rental fee has been paid and to exclude those certain channels when the rental fee has not been paid.

Abstract: A tuning system of a television receiver includes a non-volatile memory for storing tuning information. Control apparatus allows memory locations of the memory to be selectively programmed during a set-up procedure for tuning respective channels and thereafter to be selectively interrogated during channel selection. A power supply for providing a supply voltage for the memory includes apparatus for maintaining the magnitude of the supply voltage at a relatively low level when the receiver is on but the tuning system is dormant, and for increasing the magnitude of the supply voltage to a change-enabling level for a predetermined time after the operation of switches for enabling the memory to be programmed during set-up and interrogated during channel selection.

Abstract: In an infrared (IR) remote control transmitter, a main amplitude regulator is provided to regulate the amplitude of pulses applied to the transmitter's driver so as to maintain infrared radiation at a level consistent with proper operation but well below a safe limit for IR radiation under normal operating conditions. An auxiliary amplitude regulator is also provided to regulate the amplitude of pulses applied to the driver so as to maintain infrared radiation below the safe limit if the amplitude exceeds a predetermined threshold level due to a component failure of the main amplitude regulator. An average detector is also coupled to the auxiliary amplitude regulator so that the amplitude of the pulses applied to the driver is reduced should their width exceed beyond a desired value due to a component failure or misoperation of the transmitter.

Abstract: A thin metal RFI (radio frequency interference) shield for an IR (infra-red) input circuit including an IR transducer for a remote control receiver has slot-like apertures with louver-like members formed by twisting the metal between the slot-like apertures substantially 90.degree. with respect to the surface of the housing. The louvers compensate for the absence of shielding material in the apertures and thereby improve the RFI shielding effectiveness of the shield. The louver-like members also have been found to expand the field of reception or field of the remote control receiver by reflecting IR radiation coming from sideward positions into the IR transducer.