Abstract: An X-radiation protection circuit in a television receiver which permits safe operation at higher voltages and beam currents with corresponding increased video presentation brightness without the production of hazardous X-radiation by means of a control loop in which current in the high voltage sweep transformer generates a feedback signal to a conventional shutdown circuit. Excessive transformer current evidencing high electron beam current automatically lowers the turn-on voltage of the shutdown circuit providing for CRT operation at maximum safe high voltage levels and electron beam currents in accordance with "Isodose" safety curves for CRT operation.

Abstract: An electronic, microcomputer-controlled television tuning system capable of acquiring channels offset by as much as 3.25 MHz from the designated frequency while also being able to accurately tune in channels operating at the designated frequency. After synthesizing the correct channel frequency, the microcomputer looks at AFC discriminator information from which local oscillator tuning voltage direction is determined. To achieve automatic fine tuning the tuning voltage is then stepped by the microcomputer in small frequency increments which vary from 28 KHz for channel 2 to 90 KHz for channel W in the direction of the desired frequency until the center video carrier frequency is passed. The tuning voltage is then returned to the preceding step to which frequency the receiver is then locked. With essentially all broadcasting stations operating at, or very close to, the FCC-designated frequency, highly accurate tuning to the selected channel is thus permitted.

Abstract: A keyboard-operated, microcomputer-controlled method and apparatus for selecting a channel in a television receiver. Following selection of the desired channel, appropriate tuning data is stored in memory with the channel number display updated to present the selected channel until a second entry is made whereupon the selected channel tuning data is read from memory and transmitted to tuning circuitry. If a second entry is not made within a predetermined time interval from channel number entry, the system remains tuned to the previously selected channel with the channel number display reverting to the previously selected channel number. If an illegal channel number is selected, the system remains tuned to the previously selected valid channel number which is once again displayed when the second entry is made or after a predetermined time interval from channel number entry if no second entry is made.

Abstract: A video amplifier circuit for a cathode ray tube in a video display includes an anti-spot burn protection system for preventing damage to the fluorescent screen when deflection voltages are removed as in tube turn-off. A diode network in the video amplifier circuit controls the rate of voltage decay on the CRT's cathode and brightness control grid following the removal of power, maintaining a pre-determined brightness control grid-cathode voltage differential thereby precluding tube turn-on.

Abstract: A cathode ray tube (CRT) in a video display utilizes an anti-ringing system for minimizing beam scanning distortion at the start of trace. This distortion is due to velocity modulation of the scanning beam caused by high frequency, resonant energy in the inductances of the linearity and width coils and the electromagnetic deflection yoke, all of which are in series. The first half of beam scan cycle is accomplished by the conduction of the damper diode while operation of the horizontal output transistor provides beam deflection current for the second half of horizontal sweep. A low impedance is introduced in the circuit for a short period during the start of damper diode current conduction by means of a voltage biasing diode network. This low impedance dampens out high frequency resonant ringing without degrading video display performance by excessive resistive loading.

Abstract: A conventional varactor tuned VHF/UHF television tuner with additional inductors placed in parallel in each VHF tuned circuit by means of diode switching provides an additional tuning capability over the CATV Superband. Selective tuning to any broadcast channel within the VHF, UHF and CATV bands is achieved by voltage-controlled tunable circuitry such as the type employing varactor diodes responsive to an adjustable DC tuning voltage having unique levels assigned to the various desired channels. By providing an additional bandswitching input voltage to a conventional tuner, Superband coils are diode-switched in parallel with VHF tuned circuits permitting an expanded tuning frequency range. This parallel coil approach in achieving Superband coverage permits the utilization of spring-wound VHF-band and Superband coils to facilitate tuning circuit alignment and to eliminate the need for a discrete Superband tuner or a CATV converter.

Abstract: Disclosed is a UHF-VHF combination channel selector for use with varactor diode tuners in which varactor control voltage is provided by a plurality of tapered potentiometers covering the various tuning segments. Non-detent, continuous channel selection is provided by rotation of a single control shaft to which is coupled a potentiometer wiper assembly. A substantially linear tuner control angular displacement versus channel number displacement over both frequency bands is achieved by compensating for varactor tuner nonlinearity over the VHF-band with complementary VHF selector potentiometers while hyper abrupt junction varactor diode manufacturing tolerances are compensated for by normalization of the UHF selector by means of upper and lower band tapered potentiometers.

Abstract: Disclosed is a horizontal drive system and method for operating a video display capable of precisely controlling over a wide timing range the interval between the arrival of the leading edge of the input drive pulse and the initiation of the flyback pulse thus permitting the horizontal output to the video display to be synchronized to a great variety of horizontal drive input signals. The leading edge of the horizontal drive pulse triggers a variable time delay monostable multivibrator, the locked output signal of which is coupled to a precision astable multivibrator. Potentiometer adjustment of the monostable multivibrator provides for adjusting video information position with respect to raster scan while the astable multivibrator acts as the oscillator in synchronizing horizontal sweep circuitry to the horizontal input drive signal.

Abstract: A system for increasing synchronization signal injection to a free-running multivibrator in the horizontal drive circuit of a video display which enhances synchronization signal frequency capture range is disclosed. A reduction in synchronization input signal amplitude due to an input signal voltage cutoff threshold which reduces spurious multivibrator inputs is compensated for by coupling the multivibrator synchronization input signal to the emitter and collector of both of the multivibrator's coupled transistors.

Abstract: An all-channel television receiver includes a memory address counter for scanning a limited location memory for channel numbers and additional receiver adjustment information in response to a channel number input. Further television function control memories and counters for adjustment thereof are provided and accessed by the address counter. Channel numbers and additional receiver adjustment information may be programmed into and deleted from the limited location memory. Unprogrammed channels are tunable by the system at nominal levels.

Abstract: Disclosed is an SCR-analogue, dual coupled transistor vertical oscillator for synching the vertical sweep in a video display with vertical synchronization input signals. Capable of stable, free-running oscillation at two, variable DC levels, the coupled transistor configuration in combination with a capacitor generates a precisely defined sawtooth voltage waveform for controlling vertical sweep and flyback. This combination provides an inexpensive, flexible means for synchronizing sweep drive circuitry operating at various DC coupled levels with a wide range of synchronization input signals.

Abstract: A Teletext equipped NTSC television receiver system includes means for compressing the raster in the vertical direction in response to 625-line formatted Teletext signals to display normally overscanned horizontal lines on the television viewing screen. Thus 625-line formatted Teletext material may be used directly with NTSC receivers.

Abstract: A trigger pulse generation system capable of delivering a multiplicity of isolated 100 kV trigger pulses with picosecond simultaneity.