A multicontact vacuum responsive switch includes a housing divided into first and second chambers by a diaphragm. The first chamber is connected to a vacuum source while the second chamber communicates with atmospheric pressure, so that the diaphragm is movable within the housing in response to a pressure...http://www.google.ca/patents/US4892985?utm_source=gb-gplus-sharePatent US4892985 - Vacuum responsive multicontact switch
