Abstract: Improvements in a control system which maintains both the speed and the extraction pressure of an extraction type steam turbine at respective set point values by adjusting both the high pressure admission valve and the low pressure stage admission valve. Such systems are characterized by the fact that opening of the high pressure valve tends to increase both speed (for a given load) and extraction pressure (for a given extraction load); whereas opening of the low pressure valve tends to increase speed but decrease extraction pressure. The high pressure valve is positioned according to an additive function of speed and pressure errors; and the low pressure valve is positioned according to a subtractive function f(E.sub.s - E.sub.p) of such errors. The improvement resides in bounding one error signal component which influences one of the valves to a value which, for any magnitude of the other error signal, corresponds to the saturation point or physical limit of the other valve.