A pressure-sensitive switch, comprising: a base member made of electrically-insulating material having first and second surfaces and having an opening formed through a central portion thereof; a first electrode and a second electrode mounted on said second surface of said base member; a flexible diaphragm formed with plural corrugations having a peripheral portion fixedly secured in a substantially fluid tight manner to said first surface of said base member and a central portion overlying said opening formed through said base member; a post having a first end attached to said central portion of said flexible diaphragm and a second end extending through said opening in said base member, wherein said post travels freely through said opening in said base member in response to movement of said flexible diaphragm; an electrically conductive washer fixedly mounted to the second end of said post, wherein when said flexible diaphragm is exposed to atmospheric pressure, said central portion of said diaphragm moves away from said first surface of said base member and said conductive washer contacts said second surface such that said conductive washer electrically couples said first and second electrodes (100, 110) and wherein when said flexible diaphragm is exposed to a pressure substantially in excess of atmospheric pressure, said central portion of said diaphragm moves towards said first surface of said base member and said conductive washer is moved away from said second surface thereby disconnecting said first and second electrodes (100, 110) from each other; and a cap fixedly secured in a substantially fluid-tight manner to said second surface of said base member, said cap enclosing an area over said opening through said central portion of said base member, said cap providing sufficient clearance to allow movement of said post and washer beneath said cap. a base member made of electrically-insulating material having first and second surfaces and having an opening formed through a central portion thereof; a first electrode and a second electrode mounted on said second surface of said base member; a flexible diaphragm formed with plural corrugations having a peripheral portion fixedly secured in a substantially fluid tight manner to said first surface of said base member and a central portion overlying said opening formed through said base member; a post having a first end attached to said central portion of said flexible diaphragm and a second end extending through said opening in said base member, wherein said post travels freely through said opening in said base member in response to movement of said flexible diaphragm; an electrically conductive washer fixedly mounted to the second end of said post, wherein when said flexible diaphragm is exposed to atmospheric pressure, said central portion of said diaphragm moves away from said first surface of said base member and said conductive washer contacts said second surface such that said conductive washer electrically couples said first and second electrodes (100, 110) and wherein when said flexible diaphragm is exposed to a pressure substantially in excess of atmospheric pressure, said central portion of said diaphragm moves towards said first surface of said base member and said conductive washer is moved away from said second surface thereby disconnecting said first and second electrodes (100, 110) from each other; and a cap fixedly secured in a substantially fluid-tight manner to said second surface of said base member, said cap enclosing an area over said opening through said central portion of said base member, said cap providing sufficient clearance to allow movement of said post and washer beneath said cap.