Abstract: An adaptive threshold circuit for use with a magnetic type of sensor that has a pick-up coil. The pick-up coil has an alternating voltage induced therein when a slot formed in a wheel rotates past the sensor. The circuit produces a square wave pulse voltage during positive half-cycles of the voltage generated in the pick-up coil. The circuit includes a digital to analog converter the input of which is connected to a pulse counter. The output of the converter is a function of the count magnitude in the counter and provides a variable threshold voltage that is compared by a voltage comparator with a voltage that is a function of the magnitude of the voltage generated in the pick-up coil. The circuit has an input circuit connected to the pick-up coil that includes a voltage attenuating circuit and a diode.

Abstract: An apparatus for fuel level display systems comprises a fuel level sender providing a fuel level signal, a short period filter for filtering the fuel level signal through a short time constant filter, a long period filter for filtering the fuel level signal through a long time constant filter, a signal selector for selecting the long period filter output if the fuel level is above a trip point and for selecting the short period filter if the fuel level is below the trip point, and a display device for displaying a level of fuel in the tank in response to the selected signal.

Abstract: An apparatus for processing data, such as liquid level data in a motor vehicle containing a liquid storage tank, comprises a liquid level sensor for developing a signal indicative of instantaneous liquid level in the storage tank, circuitry for processing the instantaneous liquid level signal, including asymmetrical filtration of the instantaneous liquid level signal, to provide a process output signal, and a display apparatus for displaying an indication of the level of liquid in the storage tank in response to the process output signal.

Abstract: A circuit apparatus comprises interface circuitry between analog and digital circuitry. A multiple reference circuit provides a variety of reference voltage signals. The multiple reference circuitry is coupled to a selection circuit that selectively couples one of the reference voltage signals to a first reference input of the interface circuitry and selectively couples another of the reference voltage signals to a second reference input of the interface circuitry, whereby the first and second reference inputs may be selectively coupled to the reference voltages and the circuit maintains a ratiometric relationship between the digital and analog circuitry.

Abstract: A circuit apparatus for providing increased apparent resolution in digital signal processing systems includes a comparison circuit receiving an N bit digital input signal and the N most significant bits of an N+M bit output signal. The comparison circuit compares the two signals and provides a control output in response to the comparison. An N+M bit counter increases or decreases a count value which is the output signal in response to the comparison, whereby the output signal has an apparent resolution 2.sup.M better than the resolution of the input signal.

Abstract: An apparatus for applying a curve transfer function to an input signal comprises a first set of memory for storing values representing boundary points or distance differences along a curve of the transfer function, a second set of memory for storing slope values of lines connecting adjacent boundary points along the curve, a counter unit for maintaining a position count indicating position along the curve of the transfer function with respect to the stored boundary point values, an addressing unit, responsive to the position count, for selecting, from the second set of memory memory, the slope value corresponding to the position count, an accumulator for adding the selected slope value to an accumulator output value; and a comparator and data latch for determining when the accumulator output value corresponds to the input signal, and for selecting the corresponding accumulator output value as an output signal representing the application of the curve transfer function to the input signal.

Abstract: Apparatus for developing digital signals that respectively represent a plurality of different angular positions of the crankshaft of an internal combustion engine. The crankshaft drives two slotted wheels that are each associated with a sensor. Two pulse trains are developed. The first pulse train is a series of equally angularly spaced pulses. The second pulse train is comprised of a plurality of angularly spaced window pulses of different widths. Pulse falling edges of the first pulse train are counted over the duration of the windows of the second pulse train to develop digital signals that represent angular positions of the crankshaft. The system prevents edge counting until a valid edge of window pulse is detected.

Abstract: Apparatus for detecting the direction of rotation of a crankshaft of an internal combustion engine. The crankshaft drives wheels associated with sensors for developing two pulse trains as the crankshaft rotates. One pulse train is a square wave having consecutively occurring high and low periods of equal angular duration. The other pulse train is a square wave having a plurality of spaced window pulses of unequal angular duration. The relative high and low logic states of the pulse trains at certain window locations has one relationship for forward movement of the crankshaft and a different relationship for reverse movement of the crankshaft. These relationships are detected. At one of the window locations, the relative high and low logic states of the pulse trains is the same for either forward or reverse rotation. Engine reversal at this location is detected by detecting the occurrence of two consecutively occurring relative logic states that are the same.

Abstract: A digital system for providing a series of pulses that are related to the angular position of an engine crankshaft. A square wave signal is developed which is applied to the input of a synchronous digital filter. The digital filter provides a noise-immune output signal. The digital filter has two counters or timers which are used to determine whether or not the high and low times of the input signal that is applied to the filter exceed predetermined time periods. Based on this determination the filter ignores or passes pulses of the square wave to the output of the filter.

Abstract: A spark timing control for an electronic internal combustion engine ignition system that provides a constant spark advance regardless of engine speed. A series of crankshaft pulses are developed which occur at each 60 degrees of rotation of the crankshaft. The system has a source of constant frequency clock pulses which are counted up by an up-counter during 60 degree periods. The count attained by the up-counter during a 60 degree period is loaded into a down-counter. The up-counter is now counted up at a constant rate from zero and the down-counter is counted down at a constant rate from the count magnitude that was loaded into the down-counter. When the count magnitudes of the two counters are equal, a digital comparator that is connected to the counters develops an output signal that can be used to cause the firing of a spark plug.

Abstract: A control circuit for developing a digital signal for use in a closed loop dwell control of an electronic internal combustion engine ignition system. The circuit has a ramp counter and a down-counter. The ramp counter counts-up clock pulses for a period of time beginning when the primary winding of an ignition coil is energized and ending when primary winding current increases to a sensed current limit value. When current limit is reached, the most significant bits of the count in the ramp counter are loaded into the down-counter. The ramp counter is now counted-up and the down-counter is counted-down until the down-counter underflows. The final or ultimate count magnitude in the ramp counter is equal to the count attained by the ramp counter between energization of the primary winding and attainment of current limit added to a fixed percentage of the count attained by the ramp counter.