Abstract: A thermally responsive switch includes an elliptic dome-shaped metal receptacle, a header metal plate hermetically secured to the receptacle and having a through-aperture at one of two longitudinal ends, an electrical conductor inserted through the aperture of the header plate and secured with an electrically insulating material such as glass, a support having at one of two longitudinal ends a fixed portion secured to the end of the conductor in the receptacle and a supporting portion positioned away from its other end in the direction of the fixed portion, a bimetal secured at one of its two ends to the supporting portion of the support and carrying a movable contact at the other end, the bimetal having a central shallow dish-shaped portion reversing its curvature with a snap action in response to the temperature, a fixed contact secured to the header plate in the vicinity of its other longitudinal end, and a calibrator interposed between the inner wall of the receptacle and the other end of the support oppo