Abstract: A rotational speed transducer comprises a member which is mounted to rotate at a speed related to a rotational speed input. A lamp and a photocell are mounted in relation to the rotatable member such that light from the lamp is only reflected by the rotatable member toward the photocell each time a reflector portion or portions of the rotatable member comes into a particular position or positions with respect to the lamp so as to provide an electrical output, from the photocell, which is a measure of the rotational speed input. The reflector portions may be portions of a disc which constitutes the rotatable member.

Abstract: In a three electrode arc plasma flame ignition device, the first electrode surrounds the second electrode and the first and second electrodes define between them an annular gap across which the potential from a first source can be discharged, and the third electrode is surrounded by the second electrode and is so arranged that a higher potential applied to it discharges in series across a gap between the third electrode and the second electrode and radially across the annular gap between the second electrode and the first electrode.

Abstract: Bonded metallic structures comprising at least two pieces each of a metallic aluminous substance selected from the group consisting of aluminium and aluminium alloys are formed by bonding the pieces together by eutectic diffusion bonding using a metallic interlayer material which is applied between the surfaces to be joined, which forms a less stable oxide than that formed by the aluminous substance and which is preferably selected from the group consisting of copper and copper-rich alloys including at least about 95% copper.

Abstract: An actuator device includes a chamber partly bounded by a movable wall and connected to atmosphere through a permanently open orifice and an electromagnetic valve which is maintained in a closed position when de-energized and which controls the connection to said chamber of a volume of gas at other than atmospheric pressure when said valve is open.

Abstract: An air-conditioning system particularly, but not exclusively, for vehicles employs a single liquid/air heat exchanger and means selectively to supply either hot liquid or cooled liquid to said heat exchanger whereby selectively to heat or cool the air passing through said heat exchanger. As applied to a motor vehicle, the system only requires a single heat exchanger on the interior side of the vehicle bulkhead.

Abstract: An ignition device for igniting a gaseous medium, such as a fuel/air mixture, comprises a chamber having a wall provided with an aperture through which the chamber can be placed in communication with the medium to be ignited, a first electrode extending across said chamber to said aperture to define an annular gap between the tip of said first electrode and the wall of said aperture, which wall forms at least part of a second electrode, and a third electrode surrounding and insulated from said first electrode and defining a second gap within said chamber between said third electrode and one of said first and second electrodes.

Abstract: A speed responsive system, particularly for motor vehicles, whereby the vehicle may be maintained at a predetermined speed. Voltages dependent on vehicle speed and rate of change of speed are compared with a reference voltage representing a desired speed and the resultant output is compared with a periodic signal to produce output pulses of constant frequency and of a width varying with the relative magnitudes of the input voltages. These pulses are applied to an electromagnetic valve which controls the admission of pulses of reduced gas pressure from the vehicle engine inlet manifold to a chamber of variable volume and the resultant movement of a wall of said chamber is employed to control the engine throttle.

Abstract: This invention relates to a speed control system which is operable to maintain a vehicle at a selected speed, or to prevent the vehicle speed dropping below the selected speed. The system includes an electrically-operable pressure control valve which is arranged to be fed with fluid from a source of fluid pressure, for example from the transmission oil pump of an automatic transmission system, an electronic control circuit having a memory in which a selected vehicle speed can be set by the driver, and which supplies a control signal in the form of a variable mark/space ratio pulse train representative of the difference between the actual and selected speeds, to the electrically operable control valve. Fluid pressure from the pump is applied to the smaller working area side of a displaceable differential piston of a differential area piston arrangement, and the larger working area side of the differential piston is connected to the output side of the control valve.