Abstract: A thermally responsive electrical control device is operable for producing a control signal having first and second voltage levels for controlling the operation of a system actuating device for first and second modes of operation. One embodiment of the device includes a multiple bridge circuit for sensing two temperatures and for making multiple control decisions in response to the two temperatures. Another embodiment of the device includes a thermistor and a nonlinear variable resistance element which is matched in a substantially linear relation with the thermistor for compensating for the inherent substantially nonlinear character of the thermistor. Still another embodiment of the device includes a monitoring circuit which is interconnected to a bridge circuit of the device for providing visual indications of sensed temperatures without significantly interrupting the control function of the device.