An open loop feedback control apparatus for a vacuum controlled system for providing vacuum stability within a predetermined range of vacuum levels is shown. The open loop feedback control apparatus includes a vacuum regulator having a diaphragm including a valve member having a valve opening or input port which changes position as a function of the vacuum level within the vacuum system for controllably admitting or bleeding air into the vacuum system to adjust the vacuum level within the vacuum system. A transducer is operatively coupled to the diaphragm for producing an output signal which represents an instantaneous position of any one of the diaphragm valve member, valve opening or input port. A control device having a pair of inputs and an output has applied to one of the pair of inputs a set point signal representing a programmed vacuum level for the vacuum system and has applied to the other of the pair of inputs the output signal from the transducer representing an instantaneous position of any one of the diaphragm valve member, valve opening or input port. The control device produces on its output a control signal for controlling speed of a variable speed motor which drives a vacuum pump at various speed as required to enable the vacuum pump to maintain the vacuum level of the vacuum system within a predetermined range of vacuum levels.