Abstract: An electrical supply system with two power generators and several items of electrical equipment has a processor that controls disconnection of the equipment if demand should exceed supply. The processor has a hardware switch controlled by outputs from the generators. The processor runs two different programs at the same time but the switch supplies only one of these to the output. When equipment needs to be disconnected, the switch changes to supply the results of the other program to the output and this effects the disconnection. When sufficient supply is restored, the switch changes back to its original state to supply the results of the first program to the output of the processor.

Abstract: A hydraulic control system has two fluid supply circuits which control fluid pressure supplied to respective chambers of a fluid-controlled actuator, each chamber having an individual piston mounted on a common actuator rod. In normal operation, a major part of the pressure is supplied to the actuator by the first circuit in accordance with control signals derived from an external source. The second circuit supplies pressure to its respective chamber at a lower level in accordance with control signals derived from the differential pressure across the piston in that chamber, the pressure supplied by the second circuit acting to reduce the differential pressure across the piston. The system also includes a control unit that responds to malfunction of the first circuit or error in the control signals supplied to the first circuit, by disconnecting the first control circuit from control of the actuator, such as by equalizing pressure across the piston in the first chamber.