Patent US 3,931,503

A combined digital computer/analog control system for operating a boiling water reactor-steam turbine-power plant wherein one of two analog throttle pressure controllers is used for controlling the inlet and bypass valves. One of the pressure controllers is biased to provide a higher signal than the other; and such nonbiased controller is the one selected to control the valves. Each controller includes a pressure transducer, a summing device and amplifier, and a lead/lag circuit together with the appropriate power supply. A failure detection system is used to switch the controllers from automatic to manual when a predetermined combination of controller components becomes defective. Also, such system is so organized that a transducer failure for one controller causes the other controller to assume control regardless of whether such failure results in a higher or lower than proper signal.