PURPOSE: To prevent a relay from not recovering from an off state owing to noise, electricity failure for a moment, mechanical shock, etc., by setting a switching device in the way that it is turned off for a certain period after it is kept in on-state for a certain period.

CONSTITUTION: In the case that a capacitor 5 is fully charged and an input signal VIN becomes low level L3 for a second at A point of the timer 13 in the period t1 owing to some cause when the surface temperature of a carpet main body does not reach the set temperature, a switching transistor 4 is turned off and a relay 2 is thus turned off. At that time, since the off time of the input signal VIN is short, the capacitor 5 is not discharged and voltage between both ends of the relay 2 continues off-state. Soon the count time t1 of the timer 13 passes and becomes t2 and further when the period t2 comes to end and it becomes t1, the capacitor 5 is sufficiently discharged to the leading edge level and the relay 2 is turned on again. Consequently, operation of the relay continues.