Abstract: A dual slide switch voltage encoder is provided in which a plurality of analog voltages are produced as output signals of the encoder at a single output terminal. Two three position slide switches having manual actuators are utilized to provide a series of nine different analog output voltages having substantially equal increments in magnitude therebetween. A reference voltage from a microprocessor is utilized to develop these analog output voltages which are subsequently fed into an analog to digital converter in the microprocessor. Thus the present invention utilizes two three position slide switches to create a series of analog voltages having equal increments in magnitude therebetween wherein each of these analog voltages represents a different logic state corresponding to a specific combination of the various possible mechanical positions of the manual actuators of the two three position slide switches.

Abstract: An electronic ignition timing system for an internal combustion engine which rotates a crankshaft is disclosed. The ignition system comprises a plurality of variable engine condition sensors which produce corresponding analog output signals and a crankshaft position sensor. A timing control logic circuit periodically multiplexes each of the variable engine condition sensors such that they are sequentially connected as inputs to an analog to digital (A/D) converter which produces an output signal comprising a pulse train for each of the multiplexed engine conditions. The total number of pulses in each pulse train is related to the magnitude of the variable engine condition currently being connected to the A/D converter. In addition, high resolution crankshaft position pulses are produced, preferably by an electronic angle divider which receives coarse crankshaft position pulses and produces high resolution crankshaft position pulses.

Abstract: A digital signal processing circuit for controlling the spark timing and exhaust gas recirculation (EGR) of an internal combustion engine is disclosed herein. The circuit first samples the magnitude of the vacuum manifold pressure and produces a complex function analog output signal in response thereto. The output signal is produced by first converting the vacuum pressure to a digital signal, then using a read only memory to produce a complex function digital output signal and then reconverting the digital output signal to an analog output signal. The pressure analog output signal is then stored in a first holding device. Subsequently, an analog signal proportional to the period of engine revolution is sampled by the same circuit.