A pressure control apparatus, which can be used for a braking force magnification apparatus for a vehicle or a door closing and opening apparatus includes a sensor for sensing a pressure within a vacuum booster. The sensor is of a transfer-contact-type including a medial movable contact and two stationary...http://www.google.de/patents/US4596514?utm_source=gb-gplus-sharePatent US4596514 - Pressure responsive pump drive motor control apparatus having spot switch and alarm lamp
