Abstract: A backlight display system having a display screen illuminated directly by high intensity daylight lamps and illuminated indirectly by lower intensity nightlight lamps positioned to reflect their light off the daylight lamps and onto the display screen. The backlight display system includes intensity gradient filters and/or distribution lenses to enhance the uniformity of reflected nightlight, a brightness enhancement filter/diffuser disposed before the display screen, and optical filtering positioned between the illumination sources and the display screen. Photosensor controlled intensity feedback is used to provide smooth continuous dimming transition from a wide range of maximum to minimum intensity. The system also provides a third monochromatic nightlight lamp array for "class A" Night Vision Imaging System (NVIS) compatibility and an override switch to assure that lighting restrictions needed for night-vision are maintained.

Abstract: A structure employing the Hall effect for indicating the direction of a magnetic field and comprising a two-ended tubular device of a semi-conductive material and a current generating means for creating, in the absence of a magnetic field, a circumferentially uniformly distributed current flowing between the two ends of the tubular device. A plurality of conductive, wire-like elements extend radially through the tubular device toward the axis thereof and in a common plane normal to such axis and with adjacent ones of the wire-like elements being spaced apart equal angular distances. Calculating logic responds to the relative voltages induced in the wire-like elements when the tubular device is placed in a magnetic field to determine the direction of the magnetic field.

Abstract: A system for controlling the speed of a brushless DC motor includes a microprocessor for generating stator control drive signals responsive to Hall sensors detecting relative rotor-pole-stator positions. Hall sensor signal transitions are compared against a reference frequency to provide an error signal which is processed by the microprocessor. Stator commutation control signals are provided dependent upon the Hall sensor signal transitions. A control signal along with the commutation control signals are thereafter applied to integrating current drivers which provide substantially rectangular current pulses to the stator coils.

Abstract: A system for controlling the speed of a brushless DC motor includes a microprocessor for generating stator control drive signals responsive to Hall sensors detecting relative rotor-pole-stator positions. Hall sensor signal transistions are compared against a reference frequency to provide an error signal which is processed by the microprocessor in accordance with a transfer function to emulate a type II servo loop. Stator commutation control signals are reduced in duration proportional to the resulting processed error signal. The control signals are thereafter applied to integrating current drives energizing the stator coils with triangular current signals.

Abstract: The in-arm stylus cleaner includes a cleaner arm mounted for to-and-fro motion in the stylus arm carriage. To clean the stylus, the cleaner arm is retracted, the reproducing stylus is raised back up into the carriage arm, the cleaner arm is freed to allow a wiping element mounted thereon to sweep the stylus tip, and the stylus is then gently lowered onto a turntable-disposed record to resume playback operations.

Abstract: The stylus lifter driving circuit gradually lowers the stylus arm until the stylus contacts a turntable-disposed record. Once the stylus/record engagement is detected, the lifter support bracket rapidly moves away from the stylus arm to prevent stylus bouncing.

Abstract: A simplified drive circuit for applying bipolar drive current to a stepper motor includes a switch for alternately connecting a first end of the stator winding between supply potential and ground. The second end of the winding is coupled to supply potential by a resistor and coupled to ground by the parallel combination of a second resistor and a capacitor. The capacitor alternately operates as a short circuit when supply potential is applied to the first end of the winding and as a battery when the first end of the winding is grounded.

Abstract: Under certain conditions a video disc player can be responsive to externally applied interference signals to provide a defect in the display of the information recovered from the disc. Apparatus is provided which reduces the influence of the extraneous signal in the playback display. The apparatus includes a detection threshold level setting circuit which relies on the amplitude of the recovered signal during the recurring sync signals to establish the threshold at which corrective action will be taken in the player.

Abstract: A turntable drive system for use with a video disc player employs a low cost magnetic sensor, such as a Hall effect device, for turntable speed control. An integral motor mounting bracket and flux concentrator is positioned with respect to a ring magnet having a plurality of permanently magnetized poles of alternate polarity along its periphery such that the magnetic field of the magnetized ring passes through an active surface of the magnetic sensor. The Hall effect device provides an output representative of the rotary motion of the ring magnet which is fixed to the turntable. The output of the Hall effect device is compared to a reference oscillator and an error signal indicative of drift in the rotary speed of turntable from the predetermined speed is fed to a DC motor for driving the turntable at the desired rotational speed.

Abstract: A bidirectional pulse generator suitable for driving a video disc stylus deflector transducer. A differential amplifier is arranged with both its inverting and non-inverting input terminals connected for receiving a prescribed pulse waveform. First and second diodes are respectively connected between the inverting and non-inverting input terminals and a point of bilevel potential for selectively conditioning one or the other of the diodes to conduct, thereby establishing the quiescent output potential of the amplifier and concurrently shunting the pulsed waveform from one or the other of the amplifier input terminals.

Abstract: Under certain conditions a video disc player can be responsive to externally applied interference signals to provide a defect in the display of the information recovered from the disc. Apparatus is provided to reduce the influence of the extraneous signal to the playback display. The apparatus includes an automatic gain controlled amplifier and a level detector which provides two output signals. One of the output signals is used to control the amplifier gain. When the other output signal reaches a certain level it is used to develop a signal which initiates corrective action in the player.

Abstract: The burst component of a video signal recovered from a video disc record is applied to a timebase correction servo for controlling the tangential position of the player pick-up transducer in a sense to minimize timebase errors. The record is rotated at a constant angular velocity whereby, for a given displacement of the pick-up transducer, the servo loop gain tends to vary with the radial position of the transducer which, in turn, undesirably influences the servo sensitivity and dynamic stability. A loop gain compensator, responsive to a second component of the recovered video signal proportional to the playing time of the disc, regulates the servo gain at a substantially constant value thereby improving the loop stability and sensitivity.

Abstract: Video disc player apparatus for aiding the signal recovery stylus to overcome locked grooves insurmountable by normal stylus deflection transducers. The player comprises a signal pickup stylus secured to a first end of a stylus arm, the second end thereof being secured to a carriage mechanism. The carriage mechanism is driven by a servomechanism responsive to the relative stylus-carriage position so as to translate the second end of the stylus arm in consonance with the radial travel of the pickup stylus engaging the disc. Secured within the carriage is a stylus deflection transducer which cooperates with the stylus arm to selectively translate the pickup stylus past a preselected number of grooves when the stylus is prevented from normal progression by a defect occurring on the disc surface. Occasionally defects occur which cannot be bypassed by deflector induced stylus translations due to limitations in the deflector transducer.

Abstract: A video disc player is described wherein the signal pickup stylus is mounted in a carriage assembly that is advanced across the record in discreet steps, each step traversing a fixed number of information tracks. A digital processing unit, responsive to track identification numbers provides stimulus to a stepping motor to step the carriage each time the stylus has traced the fixed number of tracks.