PURPOSE: To enable a panel heat sensitive heating element to be controlled with a single type of control circuit, even when the temperature and voltage characteristics of the body are not single type.

CONSTITUTION: A heating wire 2 and detection wire 4 of a heat sensitive heating wire H are connected to each other via a resistor Rx. Current flowing from the wire 2 to the wire 4 through a heat sensitive material 3 runs through the wire 4 and the resistor Rx. As a result, characteristic voltage Vc(t) for correction temperature can be obtained at both ends of the wire 4 and resistor Rx, depending upon the temperature of the wire H. The characteristic voltage Vc(t) is given as a sum of the integral value of voltage generated due to leak current from the material 3 to each fine section of the wire 4, and voltage generated due to the flow of current through the resistor Rx after the wire 4. According to this construction, the characteristic voltage Vc(t) can be uniformly corrected at arbitrary temperature by selecting the value of the resistor Rx, even when the characteristic voltage VTC(t) for the correction temperature of the wire H becomes different due to heat generating capacity.