Abstract: A highly accurate pressure control system (200) adapted to control fluid pressure in apparatus such as the air pressure in vehicle tires (136) comprises a control module (210) having an air pressure selector (211) for selecting a desired air pressure and a pressure to voltage transducer circuit (230) for generating a signal representative of the actual air pressure. Signals representative of the difference between actual and desired air pressure are applied to comparator circuitry (246, 248) which control output switches (254, 256) for activating an inflate/deflate valve (220) to inflate or deflate the tires (136) so as to achieve and maintain the desired air pressure. Various circuitry of the control module (210) employ reference signals maintained at reference values held constant relative to a common power supply voltage instead of to a ground reference (218), thus minimizing circuit count and power dissipation while providing sufficient current for operating output switches (254, 256).