1,053,891. Thermal switches. TEXAS INSTRUMENTS Inc. Jan. 14, 1964 [Feb. 11, 1963], No. 1705/64. Heading H2B. A bimetal element 70 with a heater winding 120 and specially constructed to be undeflected by change in ambient temperature is cantilever mounted on one side of an insulating base 12 to actuate a snap-action change-over contact mounted in a cavity on the other side of the base 12, the motion being transmitted by a pin 112 slidably passing through a bore in the base 12. The element 70 comprises two bimetal strips 72 and 74, the former in the form of an open rectangle (Fig. 5, not shown) and the other a single blade carrying the heater winding 120 thereon and lying across the central aperture of the rectangle 72. The " free " end of the blade 74 is trifurcated and embraces the short side of the " free " end of rectangle 72 to interconnect these ends whilst allowing relative sliding movement therebetween. The bimetals are opposed such that no resultant movement occurs with change in ambient temperature but heating due to winding 120 affects the bimetals unequally such that 74 overcomes 72 and the contacts are actuated.