Abstract: A battery charging system includes an alternator, a main rectifier for charging the battery, and an auxiliary rectifier for supplying current to the alternator field winding under control of its voltage regulator 20. A first transistor switch is sensitive to under voltage to illuminate a first warning light and a second transistor switch is sensitive to over voltage to illuminate a second warning light. The two transistor switches are cross-connected so that failure of either light causes illumination of the other.

Abstract: A liquid level detector circuit includes a capacitive probe, a reference capacitor and two further capacitors connected as a capacitor bridge, with one terminal of each of the probe and the reference capacitor earthed and a common terminal of the further capacitors providing an output to a warning circuit. An oscillator is provided by two transistors connected so as alternately to interconnect the other terminals of each of the probe and the reference capacitor and to connect these to two different fixed potentials. The further capacitors charge slowly but discharge rapidly so that when there is any imbalance there is an excursion of the mean voltage at the common terminal during discharge which, depending on the polarity of the excursion can trigger the warning circuit.

Abstract: A starter motor control circuit for an engine includes an input circuit which is controlled by the ignition contact breaker of the engine, the capacitor charging each time the contact breaker opens and discharging relatively slowly when it is closed. The capacitor is connected by a complementary emitter follower transistor pair to a level detector circuit which produces an output when the voltage on the capacitor is between predetermined limits. At below a predetermined speed this output is a train of constant length pulses which control charging and discharging of a further capacitor. When the voltage on the capacitor is less than a predetermined minimum a regenerative switching circuit is operated to cut out the starter circuit. A feedback transistor maintains the capacitor discharged until the engine stops.

Abstract: A spark ignition system includes a variable reluctance pick-up providing the input signal to a saturating amplifier which includes a feedback path constituted by a capacitor and a resistor in series. This amplifier has a transfer function while it is being driven towards saturation, such that its output is the sum of an integral part and a proportional part and does not saturate as a result of oscillatory high frequency spurious signals since these have a low integral. A resistor in the input of the amplifier is shorted out by a diode connected transistor when the polarity of the signal from the pick-up reverses, to increase the gain of the amplifier while it is being driven towards de-saturation, such change of polarity signalling production of a spark.

Abstract: An i.c. engine fuel system uses a conventional carburettor modified by the addition of an air pressure control to the float chamber thereof. The air pressure control includes a bank of valves connected in parallel to exhaust a chamber connected by an orifice to the engine intake manifold. The chamber is connected to the float chamber and the valves are controlled by the individual bits of a digital output signal produced by a digital read only memory addressed by digital signals corresponding to two engine parameters such as engine speed and throttle angle.

Abstract: A road vehicle electrical system has an alternator which provides power through a rectifier to a battery, and also supplies a third supply line used for feeding an ignition warning lamp. Control means for the starting system of the vehicle is associated with the supply lines in such a way that once the engine has started and the third supply line is energized, a further attempt cannot be made to start the engine until the engine has stopped.

Abstract: A temperature sensitive electronic switching arrangement has a casing with two terminals, one of which may be constituted by the casing. In the casing is a positive temperature coefficient resistor and associated trigger circuit. As the temperature rises, a point is reached at which the circuit between the casing terminals changes from a high resistance to a low resistance. The arrangement has many uses, particularly in road vehicles.

Abstract: A liquid level detection system has a monitoring device which contacts the liquid when the liquid level is above the predetermined level, and a positive temperature co-efficient resistor mounted in the system at the position where the temperature is to be sensed. The components are connected up in such a way that a warning is given if the liquid level falls or the temperature at a given point rises beyond a predetermined value.