Abstract: A push-pull amplifier having like conductivity output transistors is driven by a phase-splitter transistor amplifier. The collector load of the phase-splitter includes a diode bridge for establishing the amplifier idling current. One arm of the bridge incorporates the pull-up output transistor base-emitter junction-the current conducted therein being accurately determined by bridge parameters.

Abstract: Video disc stylus holders are designed to provide vertical decoupling of the pickup stylus from the stylus support arm. The compliance designed into the holder gives rise to mechanical resonant modes which affect the recovered signal in the audio range. A rigid damping element secured to the compliant section of the stylus holder by a lossy adhesive or a lossy mass rigidly secured to the compliant section of the stylus holder reduces the amplitude of the resonant modes.

Abstract: An automatic gain control arrangement is provided for an analog to digital (A/D) converter in a television signal processing system. A gain-controlled source of analog signals applies a video information signal to the input of an A/D converter. The A/D converter produces digitized video signal samples at an output which is coupled to a digital peak detector. The digital peak detector detects the level of the digital samples of the synchronizing signal components. The detected sync signal level is compared with a desired value or range of values. If the detected sync signal level is not at the desired level or is outside the desired range, the count of a counter is incremented or decremented accordingly. The count of the counter is converted to an analog voltage which is applied to the gain-controlled signal source to control the level of the analog signal applied to the A/D converter.

Abstract: A digital filter is provided which selectively employs binary arithmetic and offset two's complement arithmetic in an adder ladder to protect against signal overflows and underflows, as well as to minimize adder size. Signal overflows and underflows are prevented by performing subtraction and certain additions in offset two's complement notation, while adder sizes are minimized by performing certain other additions in binary notation. In an alternate embodiment, positively weighted values are combined by binary addition in a first adder ladder, and negatively weighted values are combined by binary addition in a second, parallel adder ladder. At the outputs of the two ladders, the two sums are converted to offset two's complement notation, and the negatively weighted sum is subtracted from the positively weighted sum.

Abstract: A differential amplifier stage is disclosed which utilizes opposed pairs of complementary transistors. The emitter electrodes of the complementary transistors of each pair are connected via matched resistors. A second matched pair of resistors are connected between the emitter electrodes of the input transistor of each complementary transistor pair. The interconnection of the second match pairs of resistors is connected to the base electrodes of the other transistors of each complementary transistor pair by a diode. A constant bias current is applied to the diode-transistor interconnection to provide current to the second pair of resistors to develop like potentials. These potentials establish floating bias potentials across the matched resistors in the emitter circuits of the complementary transistor pairs and thereby establish bias current in the transistors.

Abstract: A differential current amplifier includes a differential input transistor pair having respective first and second unity gain current mirror amplifiers (CMA) connected in their respective output circuits. The output terminal of the CMA connected in the output circuit of the first transistor of the differential pair is connected to the input terminal of the second transistor of the differential pair. The output terminal of the CMA connected in the output circuit of the second transistor is connected to the input terminal of the first transistor. The current feedback to the input terminals of the differential pair conditions them to be responsive to input signal currents. An amplifier output current can be derived from an additional current output from one of the first and second CMA's, the additional CMA output having a gain of A relative to the unity gain output.

Abstract: A video disc player apparatus having a signal pickup stylus secured to a stylus arm for recovering recorded signal from a disc record, wherein the stylus arm is mechanically biased by a spring force to produce a positive stylus-disc pressure, includes apparatus cooperating with the stylus arm to maintain the stylus-disc pressure generally constant in the presence of stylus-disc displacements normal to the disc surface. A permanent magnet is secured to the stylus arm with its interpolar axis transverse to the stylus arm and substantially parallel to the disc record. First and second coils, coaxially aligned are disposed on either side of the magnet and arranged with their axes parallel to the interpolar axis of the magnet. Energizing currents are applied to the first and second coils creating respective magnetic fields which produce forces repulsive to the pole of the permanent magnet proximate thereto.

Abstract: A power amplifier circuit includes an output complementary emitter-coupled transistor pair driven by a second pair of complementary transistors having a parallel resistor diode combination serially connected between their emitters to establish idling currents. Base drive for the output transistors flows through the resistor of the resistor-diode combination until the potential thereacross exceeds the diode forward breakdown potential after which all increases in drive current pass through the diode. The use of the diode limits the bucking potential in the base current drive circuit thereby enhancing available output power.

Abstract: A digital memory is provided which contains digital data words representative of a desired symmetrical transfer characteristic of a digital signal processor. Digital signals which are to be processed are applied to the address inputs of the memory, producing output signals in conformance with the desired transfer characteristic. Advantage is taken of the symmetrical nature of the response characteristic to minimize the size of the memory. Data words corresponding to only a portion of the full dynamic range of the digital signal processor are stored in the memory, and memory locations are addressed and read out in accordance with the value of a polarity-determining bit of the input digital signal, with the output signals being translated over the required full dynamic range in accordance with the value of the polarity-determining bit.

Abstract: In a system for recording digital information on a video disc and for playback of the digital information therefrom, the digital data is recorded in synchronism with the color subcarrier signal on a horizontal line adjacent to a constant luminance line. This arrangement facilitates a video disc player having a simple, efficient, video-to-digital interface for separating the prerecorded digital information from the video signal. The player apparatus is responsive to the color subcarrier signal and the chrominance-related output signal of a comb filter, both of which are normally available during video signal processing. Prerecorded digital information representing field number and type of program content is used by a microprocessor controller to provide player features such as locked groove detection, program elapsed time display, and end of program indication.

Abstract: A threshold comparator for use with a dual slope A/D converter has its input potential established at its threshold potential during auto-zeroing. Potential offset means is included in the auto-zero feedback loop around the integrating and output amplifiers of the A/D circuit. Bias current applied to the potential offset means substantially tracks current passed in the comparator so that the potential developed by the potential offset means substantially tracks the threshold potential of the comparator.

Abstract: An adaptive video disc record stylus kicker system for inducing limited stylus translation radially across the disc record. Control circuitry responsive to track identification signals recorded on the disc and to player commands evaluates the error between actual kicker induced stylus translations and the programmed kicker induced stylus translations to calibrate the stylus kicker drive signals.

Abstract: A servo system for a VideoDisc player stylus carrying carriage assembly is described which precludes the servo system entering a hunt mode due to the signal pickup stylus tracking an eccentric signal track. The player comprises a carriage for housing a track following signal pickup stylus compliantly mounted therein. A position detector generates an analog signal proportional to the stylus position relative to a relaxed or centered position. The position signal is converted to a bilevel signal (i.e. relatively positive and relatively negative levels), the two levels corresponding to the stylus being to the right or left of the centered position respectively. The bilevel signal is sampled at regular intervals, e.g. eight, per disc revolution. Counter circuitry counts the number of samples per disc revolution which are at the relatively positive level.

Abstract: A retainer for holding the stylus arm of a video disc signal pickup cartridge is described which is low cost and occupies little space in the cartridge. The retainer is formed from flat spring stock and shaped to have a three-sided body with fingers extending from the parallel sides to encompass and hold the stylus arm. The retainer is inserted through a top wall of the cartridge and spring tabs which are formed in the sides of the retainer body engage opposite surfaces of the top wall to secure the retainer thereto.

Abstract: Assembly of a video disc signal recovery stylus apparatus is facilitated by utilizing a stylus holder having a vertical cylindrical end. A conductive leaf spring is inserted in the cylinder followed by a conductive torroidal elastomer. The stylus is then inserted in a hole in the elastomer, all of the parts being held in place by the compressive forces exerted by the elastomer. The second end of the leaf spring is secured to a terminal element which is releasably secured to the stylus arm to provide mobility of the foregoing subassembly during manufacturing. When the subassembly is inserted into a cartridge the terminal element is detached from the stylus arm and inserted into a conformal cavity in the cartridge affording accurate positioning and orientation of the leaf spring.

Abstract: A video disc signal pickup cartridge is described wherein the stylus arm is coupled to the cartridge body by a highly compliant relatively long, flat member suspended vertically from the top wall of the cartridge. The stylus arm is coupled to the member by passing one end of the arm through a tight fitting hole in the distal end of the member. The member is necked down near the hole to increase torsional compliance with respect to axial rotation of the stylus arm. The proximate end of the member has an expanded compliant region which is compressed for passage through a mounting hole in the cartridge body and allowed to re-expand to compressively retain the member in the hole.

Abstract: Impulse noise detection circuitry for determining the occurrence of short noise pulses in TV video signal includes two 1H delay lines to align successive image lines for signal comparison. The amplitude of signal from one image line is compared with the signal amplitude of a succeeding and a preceding image line along a vertical line. If the amplitude of the one signal concurrently exceeds the signal of both the preceding and the succeeding image lines, then a control signal, indicative of the presence of impulse noise, is produced.

Abstract: A digital output tapped filter is provided in which the filtered output signals are latched into a first latch circuit by the clock signal which clocks the serial shift register. Output signals are thereby held in the register during the time that new data values from the shift register are propagating through the adder tree and weighting function circuits. By the time that the clock signal again clocks the shift register, the filter output signal has settled, and can again be latched into the latch circuit. The signals at the output of the latch circuit are thus immunized from signal ripple. A second latch circuit is coupled to the output of the first latch circuit, and is clocked by the same clock signal as the first latch circuit. Consecutively produced filtered data words are thereby held in the latches, and the latched signals of N bits are applied to inputs of an N bit adder. The N bit adder produces an output signal of N+1 bits.

Abstract: A differential amplifier is arranged to exhibit substantially no D.C. offset or drift. Input signal is alternately connected to the non-inverting and inverting input terminals of an input differential stage. Synchronously therewith the differential output signals of the differential stage are interchanged to maintain the sense of the output signal constant. The synchronous interchanging of differential input and differential output signals tends to average out parameter offset in the input circuit elements. The differential input stage is provided with a substantially balanced active current mirror load. The current mirror load devices are commutated with respect to the input devices to further reduce amplifier offset arising inherently in the differential stage load elements. The commutation of the current mirror load elements is performed at a rate which is a multiple of the rate at which the input and output signals are interchanged.

Abstract: A video disc player designed to play video disc records having either non compressed monophonic wide band audio signals or video disc records having compressed stereophonic limited band audio signals recorded thereon. The player includes expander circuitry which may be selectively operated as a time invariant amplifier in the absence of stereo audio signals and as an amplifier with a time varying transfer function for expanding the stereo signals. The expander circuit operating mode is controlled by a circuit which detects the presence of a second or stereo sound carrier in the signal recovered from the record being played. Concurrently with the amplifier being rendered time invariant during the playback of monophonic records, electronic filter circuitry is switched into the amplifier circuitry to reduce the monophonic audio bandwidth and effectively increase the resultant audio signal-to-noise ratio.