Control system for coupling redundant logic channels

In a nuclear reactor electrical control system wherein redundant logic channels are maintained electrically isolated and physically separated with a serial fiber optic light transmissive link between the logic channels, and a plurality of independent reactor condition sensor means are electrically connected to respective electro-optic channel coupling means which are coupled to respective logic channels, which electro-optic channel coupling means includes an electro-optic channel coupling means includes an electro-optical modulatable medium the light transmission characteristic of which is variable in response to reactor condition electrical signals from the respective sensor means, and wherein fiber optic input and output cables connect the channel coupling means to a light input source and a light output detector means from which a reactor control signal is generated in response to predetermined reactor system conditions as indicated by the sensor means, and wherein when all of the plural sensor means generate equal signals of a value indicative of normal reactor operating condition the light transmission to the detector means is maximized, and wherein when the plural sensor means generate unequal signals which result is reduced light transmission to the detector means this is indicative of a possible out of tolerance reactor condition, and wherein when all of the plural sensor means generate an equal signal of a value which is indicative of an out of tolerance reactor condition the light transmission to the detector means is reduced to a value indicating a confirmed by plural sensor means out of tolerance reactor condition.