Abstract: A control system for an industrial plant comprises a plurality of instrument sets and a plurality of logic sets.The instrument sets have a number of sensors which detect parameters of the industrial plant, and have two serial link controllers which supply the output signals from each sensor in the instrument set sequentilly to the logic sets.The logic sets have a number of auto select logic circuits, each of which selects data from the sensors from one of the instrument sets, and a synchronister ensures that the output signals from the sensors detecting the same parameter are supplied to a voting logic circuit at the same time. The voting logic circuit performs a voting function on the output signals to produce a series of high reliability signals which are converted to parallel high reliability signals by a series to a parallel converter. The high reliability signals are supplied to a fault logic shutdown circuit which controls the operation of shutdown mechanisms for the industrial plant.