Abstract: A processing circuit is provided for use in an optical combustion monitor for an internal combustion engine. The circuit includes a variable gain amplifier for amplifying a signal from one or more opto-electric transducers sensitive to combustion light in the engine cylinders. A gain control circuit including a peak detector controls the variable gain amplifier so that the peak amplitude of the amplifier output signal is substantially constant.

Abstract: A line driver is provided for driving a twisted pair of lines with complementary data signals. The driver comprises NPN and PNP transistors arranged as complementary emitter followers with their emitters connected to a biasing resistor network to provide an arrangement capable of being used as a "wired-or" output.

Abstract: The extent to which a throttle can be opened is determined in accordance with a "lowest wins" philosophy. This is achieved by a transmission mechanism disposed between the accelerator pedal and the throttle valve and comprising an interlock collar fast with a rotatable shaft for operating the valve, a spring normally urging the shaft in a direction to open the valve, and first and second input collars rotatably mounted on the shaft and coupled respectively to the pedal and to a motor device operable in response to signals from electronic means in accordance with at least one appropriate parameter. The input collars are arranged to co-operate unit the interlock collar in a manner such that the angular position of the interlock collar is determined by the position of that one input collar what has moved by the smaller distance from a given retracted position.