Abstract: In order to reduce the reflectivity of an apodized surface acoustic wave transducer, one portion of the dummy area thereof is bare and another portion is 100% metallized, and the boundary between these two regions is shaped to equalize total acoustic transit times across the transducer aperture. This avoids any net refraction, and thus permits any acoustic wavefronts which traverse the two regions to remain flat.

Abstract: An improvement in an anode contact spring for use in a color cathode ray tube is disclosed. The improvement comprises positive locking means for locking an attachment end of the contact spring to a supportive member for suspending the shadow mask adjacent to the panel. The positive locking means comprises bolt means extending from the supportive member and which is located in a preselected lateral position on the member. Clasping means on the attachment end provide for clasping the supportive member. One leg of the clasping means is a hasp for engaging the bolt. An anti-twistoff fold is provided in the contact spring adjacent to the attachment end. Upon engagement by manual pressure of the clasping means with a supportive member, the clasping means expands to provide engagement of the hasp with the bolt, then contracts to provide push-click positive locking of the contact spring to the supportive member.

Abstract: A system is disclosed for utilizing command buffers in a microprocessor controlled electronic code keyer for storing, rather than text to be transmitted, command strings for keyer operation. The command string is defined by a series of keypad closures for selecting a sequence of text buffers to be transmitted. In addition, the command buffers may be used during automatic text transmission to selectively change keyer parameters such as the speed of character transmission, inter-character and inter-word spacing, dot-to-dash-to-space ratio, or the number of times the contents of a text buffer will be automatically repeated. The use of text and command buffers permits the formation of essentially errorless Morse code transmissions, substantially enhances keyer operating and makes more efficient use of available memory.

Abstract: An equalizer and decoder system compensating for multipath distortion in digital format signals sent by teletext, for example. The system loads demodulated data signals and a received reference signal into a charge coupled device clocked in real time by a clock circuit. Later, the reference pulse is clocked to a microprocessor which determines tap coefficients for a transversal filter to correct the multipath distortion in the reference signal. The data signals are then applied to a transversal filter weighted with the calculated tap weights. After filtering, signals are decoded by the microprocessor.In another embodiment a charge coupled device with tapped stages is used at one time for receiving the data signals in real time, and at a later time for part of a transversal filter.In a simplest embodiment, distortions are removed by the microprocessor itself, without any separate transversal filter.

Abstract: A mode decision controller is described for actuating a conventional chrominance bandwith enhancement scheme in a color television receiver. A video signal detected by the receiver typically includes a relatively wide band luminance element and a relatively narrow band chrominance element, each of which are processed by the enhancement scheme to develop their first derivatives for use in enhancing the bandwith of the chrominance element. Either of these derivatives may be used as an input to the mode decision controller. The selected derivative is applied to a filter for removing components therefrom which extend above a given frequency range, thereby developing a frequency-limited output signal whose time domain exceeds the time domain of the selected first derivative. A signal processor receives the frequency-limited output signal and compresses its time domain to develop a control signal whose time domain is substantially equivalent to the time domain of the selected first derivative.

Abstract: Video display distortion in a television receiver introduced by input voltage excursions is compensated for by a voltage regulation circuit which tracks the changing input line voltage while automatically switching to an active filter mode once the line voltage has decreased to a predetermined level. This permits the removal of AC transients from the fluctuating input signal and avoids display degradation resulting therefrom.

Abstract: An electronic switch is provided for use in a battery-powered portable television receiver which eliminates power supply current drain when the television receiver is turned off. Coupled transistors are rendered conductive by means of either a clock or a manually switched input signal to provide a direct voltage battery output to television receiver circuitry. Also disclosed in an electronic switch combination for selectively controlling the audio output for the entire television receiver either manually or automatically.

Abstract: Apparatus and method is disclosed for spot-knocking a cathode ray picture tube by beneficial arcing between selected electrodes of an electron gun sealed in the evacuated envelope of the tube. The invention is particularly useful in spot-knocking certain cathode ray picture tubes having a resistive arc-suppression means and static elimination system. The picture tube has an inherent capacitance that can store energy in an amount capable of inducing destructive arcing during spot-knocking. In one embodiment of the invention, a bipolar potential is applied across the electrodes to be spot-knocked, resulting in the amount of energy in the induced arcing, for a given applied potential, being very much less than would be the case if a unipolar potential were applied. Other embodiments include resistive means and spark gap means for discharging the voltage between lead-in pins before a destructive arc can occur therebetween.

Abstract: Disclosed is a DC-coupled video amplifier with AGC feedback having a stable operating point. Shifting of sync tip DC level resulting in a loss of synchronization of the video signal is compensated for by means of a feedback loop in the video amplifier thus providing a level video output signal.

Abstract: A phasing circuit is described for automatically controlling the phase of an oscillator input to a synchronous detector which demodulates a video signal in a television receiver. A conventional phase locked loop develops an oscillator signal whose phase tracks with variations in the phase of a video intermediate frequency (I.F.) signal applied to the loop. The automatic phasing circuit includes a phase adjustment network for coupling the video I.F. signal to the phase locked loop and for varying the phase of the latter signal input to the loop in response to a phase correction signal. The phase correction signal is preferably developed by a multiplier which senses the video I.F. signal and the input to the phase locked loop and controls the phase adjustment network such that the latter network varies the phase of the video I.F. input to the phase locked loop until the phase of the oscillator signal has a selected phase relationship to the video I.F. signal input to the synchronous detector.

Abstract: A tint control circuit is described for use in a color television receiver. The circuit generates four currents having substantially equal D.C. components, and having respective 3.58 MH.sub.z subcarrier components of four different quadrature phases. The phase of each such current is preferably variable over a range of .+-.45 degrees. In a preferred embodiment, the four currents are coupled to a matrixing network for developing a pair of subcarrier output voltages whose phases differ by more than 90 degrees and whose D.C. components are substantially equal. As the phases of the four currents are varied, the phases of the subcarrier output voltages vary accordingly, but maintain their phase relationship to each other.

Abstract: A ramp generator is described for developing a ramp voltage for use in vertically deflecting the electron beam or beams of a television receiver. The ramp generator receives a vertical rate pulse developed by the receiver for developing a charging current during the occurrence of the vertical rate pulse. A discharging current is also generated, and both currents are applied to a capacitor for developing a ramp voltage which increases and then decreases in amplitude. A clamp circuit in the generator is enabled when the vertical pulse is received for clamping the ramp voltage on the capacitor to a predetermined peak voltage via low impedance path such that unwanted voltage components are substantially eliminated from the ramp voltage during the clamping action.

Abstract: Disclosed is a power supply having transformer isolation which is capable of providing a plurality of precisely regulated output voltage levels. This regulated power supply is particularly adapted for use in a video display terminal because the output voltages may be scan-derived for improved video presentation with a plurality of precise voltage levels for driving various terminal logic levels provided by a single DC signal source.

Abstract: An improved metal detecting device of the beat frequency oscillator type is provided which incorporates a method for determining the side of the zero beat frequency at which a search oscillator is operating. The device includes a search coil conveniently mounted which is part of a search oscillator. A reference oscillator is also provided, the output of which is digitally compared to that of the search oscillator by a digital phase comparator. The digital phase comparator output is applied through a low pass filter to a slope detector circuit. The slope detector output signal is supplied to both an audio output circuit and a filter/comparator. The audio output is sufficient to facilitate location of permeable and conductive substances. The output of the slope detector also contains information which is extracted by the filter/comparator and translated to an audible signal by an oscillator and the audio output circuit.

Abstract: A sample and hold detector is described which preferably includes a differential amplifier, a current mirror and a storage capacitor which is charged and discharged to the voltage level of an electrical input signal during appropriate sampling intervals. The differential amplifier receives the electrical input signal as one input and the capacitor voltage as a second input for generating, at first and second differential amplifier output ports, currents which are a function of the voltage difference between its inputs. To charge and discharge the capacitor, the latter is coupled to the differential amplifier's second output port via a current path, and the current mirror is coupled between the output ports of the differential amplifier for sourcing to the second output port a predetermined percentage of differential amplifier current generated at the first output port.

Abstract: An easily installed thermal coupler inserted in the extruded section of a heat sink on which a transistor amplifier is mounted and positioned on a circuit board in thermal contact with diode biasing means coupled to the transistor amplifier. By thus thermally coupling the biasing means with the amplifier in a self-correcting, negative feedback loop, stable transistor operation is achieved and thermal runaway prevented. Employing a unitized metallic heat conducting member having a base plate including connecting studs for circuit board mounting and an upright member extending therefrom, the heat coupler may be used as either a heat sink or heat transfer device in carrying heat either out of or into the circuit board.

Abstract: Disclosed is a microcomputer-controlled system and method for detecting a vertical synchronization pulse extracted from a composite synchronization signal provided to a television receiver. Sync pulse voltage level, period and duty cycle are analyzed in terms of predetermined vertical sync criteria in detecting valid vertical synchronization.

Abstract: A pulse width modulator is described for width-modulating horizontal rate pulses developed in a television receiver and for applying the width-modulated pulses to the receiver's horizontal drive system. In the illustrated embodiment, the modulator includes a differential amplifier which senses the receiver's high voltage and beam current to develop a control signal which varies in accordance with variations in the beam current and the high voltage. A second differential amplifier receives the control signal and horizontal rate pulses for developing pulses whose width is varied in response to variations in the control signal. The width-modulated pulses cause the horizontal drive system to generate a substantially constant horizontal picture size despite variations in line voltage and brightness.

Abstract: A voltage regulator is described for use in a television receiver having a horizontal oscillator for exciting a horizontal sweep system and a power source for energizing the receiver. In a receiver which also includes a voltage source derived from the excited sweep system, the regulator preferably includes an input port for receiving current from the power source and a circuit responsive to that current for initially energizing the horizontal oscillator so that the sweep system becomes excited. The regulator also includes an input/output port for receiving current from the sweep-derived voltage source and an on/off switch which is turned on responsive to the input/output port being driven above a minimum voltage level. The "on" condition of the switch enables a series pass regulator for coupling current from the input port to the input/output port such that the latter port is held at a regulated voltage level.

Abstract: An all-electronic, integrated television channel tuning indirect frequency synthesis system capable of operating over the VHF, UHF and CATV spectra in which digital bandswitching is accomplished automatically. Keyboard selected control inputs are provided to a microcomputer for the generation of digital bandswitching signals and, in combination with a phase locked loop, tuning voltages. The bandswitch signals and tuning voltages are provided to a tuner having several resonant frequency circuits, each including a varactor diode and a plurality of coupled inductors and switching diodes.