Abstract: An apparatus for measuring an absolute temperature or a temperature differential. The apparatus uses two temperature sensitive switching devices exhibiting regenerative switching action at a power level which is dependent on the temperature sensed by such switching devices. Means are provided for simultaneously applying an increasing voltage to such switching devices to make them switch, and a detector is connected to both switching devices for measuring the time interval between switching of the first and second switching devices and for providing an output which is proportional to the absolute temperature sensed by the switching devices or to the temperature differential sensed by the switching devices. A display device is connected to the detector for providing a visual indication of the absolute temperature sensed or of the temperature differential sensed.