Abstract: A control circuit for an electrically driven vehicle which employs a separately excited motor. The armature is connected in series with a current control between two supply rails. The field winding is likewise connected between the rails, but has associated with it switch means for reversing the connection of the field winding. A diode arrangement is provided for recirculating current when the field circuit is interrupted and for establishing a recirculating path through the vehicle battery when the field connections are reversed, by the switch means.

Abstract: A vehicle transmission having a casing including a lubricant sump, a rotary shaft and a differential unit in the casing, drive means between them and a lubricant pump driven by the shaft to lift lubricant from the sump and discharge it onto the moving parts.

Abstract: In a method of forming a sintered, ceramic product, aluminium nitride is reacted with silica at a temperature of between 1200.degree. and 2000.degree. C to form a single phase silicon aluminium oxynitride ceramic material, the reaction mixture at said temperature containing not more than 60% by weight of the aluminium nitride and also containing first and second metal oxides other than silica. The metal oxides are arranged so that they do not introduce into the mixture a combination of magnesium oxide and alumina alone and further are arranged so that during the reaction they combine with part of said silica to form a silicate glass having a liquidus temperature below that of the silicate glass which would be formed from silica with either of said metal oxides alone. The silicate glass formed then aids densification of the ceramic material during sintering.

Abstract: A d.c. control circuit includes a slew-rate limiting circuit interposed between a current sensing device which detects current in a load and a control circuit, for switching on and off a thyristor controlling current through the load. The circuit limits the slew rate to a level in excess of the maximum normal current slew rate through the load.

Abstract: A full wave rectifier comprises positive and negative supply lines, and a differential input amplifier which is powered by the positive and negative supply lines and which has its inverting input terminal connected through an impedance to an input terminal to which the a.c. signal to be rectified is fed. The non-inverting input terminal of the differential input amplifier is connected to a terminal at a potential intermediate the positive and negative supply lines, and a transistor has its base connected to the output terminal of the differential input amplifier. The emitter and collector of the transistor are connected through resistors to the supply lines, while the emitter of the transistor is also connected through an impedance to the inverting input terminal of the differential input amplifier, the output of the full wave rectifier being taken from the collector of the transistor.