Abstract: A processor controlled fluorescent lamp dimmer circuit is shown for use in an aircraft display system utilizing a fluorescent lamp in the backlight system of individual LCD display devices. By use of a processor control dimming circuit in control over each LCD display, greater flexibility, e.g., as by adjustment in software parameters, is made possible in the operation of a dimmer control circuit. The dimmer control circuit reacts to such conditions as ambient light within the aircraft cockpit, fluorescent lamp light energy output, and fluorescent lamp temperature to provide substantially consistent actual and perceived luminance on the LCD display as a function of such detected conditions. Furthermore, the processor control achieves the desired luminance without over-driving, and therefore deteriorating, the lamps. As a result, the pilot of the aircraft enjoys a more reliable and consistent LCD display and need not be distracted by variation in luminance of the LCD display in operation of the aircraft.

Abstract: A circuit operable in two modes alternatively to provide a digital-to-analog converter capability and an analog-to-digital converter capability is disclosed utilizing a single digital multiplexer at a digital input and two analog multiplexers to control signal path routing. A track-and-hold circuit is utilized in the analog-to-digital configuration as a sample-and-hold, and alternatively in the digital-to-analog configuration as an operational amplifier.

Abstract: Switching apparatus for connecting a device requiring a backup power source to a battery bus upon disconnect or failure of the primary power source, without interruption of power, and without loading the backup power source when the device is off. Therefore, the apparatus provides nearly total or complete isolation of the backup source from the load when the device (load) is off.

Abstract: A magnetic field sensor is illustrated which in one useful application comprised two orthogonally positioned coils each having its own electronics and each wound on separate small strips of core material and positioned in a gimballed fixture for use as an electronic compass. The sensing coils in each sensor sense only the components of magnetic field in that plane with one output being representative of the field along the axis of one of the coils and the other being representative of the field along the axis of the other coil. A secondary winding cooperating with each of these coils provides an output signal which is operated upon to remove any DC components and provide a signal indicative in waveshape of the flux in the core. Opposite polarity peak detectors are then used to determine the relative peak voltages with respect to ground for the purpose of determining the DC component which had been removed. The DC component is indicative of any external fields affecting the flux levels in the core material.