THERMOSWITCHR temperature controllers are tubular devices featuring an outer shell made of a high-expanding metal and internal struts made of low-expanding metal, with a pair of electrical contacts between them. When the temperature of the media being measured changes, a corresponding change in the spacing of the contacts provide instant on/off control with a small differential, resulting in I1F precision, depending upon the application. They provide >100,000 cycles of operation at 10 A and 120 VAC.