An inertia switch for a supplemental inflatable restraint system. The switch comprises a casing that is divided into two chambers by an axially movable diaphragm. In one embodiment, the diaphragm carries an electrical contact on one face and an inertial mass on the other. A pair of terminals are disposed in the path of travel of the electrical contact so that when the switch is subjected to axial deceleration force the contact is urged toward the terminals. Actual contact is made when the deceleration force equals or exceeds a predetermined deceleration characteristic. The deceleration characteristic is a function not only of the diaphragm, the electrical contact, and the mass, but also of a control orifice located in an orifice that communicates the two chambers with each other. The chambers are constructed such that air is forced from one chamber into another through the control orifice when deceleration occurs and this imparts a dampening to the motion of the diaphragm. Another embodiment for sensing deceleration places the inertial mass in the one chamber that contains the contacts. The other chamber has a thin concave-convex shape that gives the switch a low profile. The switch has a molded plastic base containing a test coil for attracting the inertial mass to test the switch. A mechanism for calibrating the switch is also included.
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