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: An arch form comprises a tooth portion including a plurality of integral teeth injection moulded in pastics material and arranged in a curved row, and a gum portion in situ injection moulded onto the tooth portion so as to overlie an upper surface thereof. An undulating ridge extends along the upper surface of the tooth portion and is surrounded by the gum portion. Front teeth of the tooth portion have a substantially natural inclination with respect to the general plane of the tooth portion, whereas rear teeth thereof are inclined towards the front teeth such that their direction of extent is angled at 10.degree. to 20.degree. with respect to their counterparts in a natural set of teeth.A method of moulding the arch form requires the provision of a two-part mould defining the shape of the tooth portion, and a further mould part defining the shape of the gum portion.

Abstract: A fluid pressure transducer includes a hollow body divided into first and second compartments which are sealed from one another, the first compartment being connected, in use, to a first source of fluid at a pressure to be monitored, while the second compartment is connected to a reference source. The compartments include a common wall which is deformable in response to variations in the pressure of the first fluid source as compared to that of the reference source, and received within the body are a carrier and a first abutment member which are capable of relative movement towards and away from one another in resonse to deformation of the common wall. A plurality of further abutment members are resiliently supported by the carrier and arranged so as to become engaged with or disengaged from respective portions of the first abutment member at different positions of the first abutment member relative to the carrier.

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 spark ignition system for a vehicle produces pulses representing the engine crankshaft angle. These pulses are counted, and compared with a datum signal which varies in accordance with engine conditions. When the two signals compared are equalled, then a spark is produced.

Abstract: A headlamp wiper assembly for a motor vehicle having twin headlamp units. The assembly comprises a backing plate having a pair of apertures therein to accommodate the twin headlamp and a further offset aperture which accommodates a wheel box unit. A shaft of the wheel box unit carries a single wiper blade and is oscillatable through substantially 180.degree. so that the wiper blade can clean both headlamps. The wiper blade is parked, when not in use, so as not to obscure the headlamps.