| 摘要 |
PURPOSE:To improve the effect of saving of electricity, by detecting whether a person is using a foot warmer or not by an ultrasonic signal, etc., and controlling to throw a current to a heater by the detected signal. CONSTITUTION:The signals dispatched from a high-frequency oscillator 16 and a low-frequency oscillator 17 drive a ultrasonic transmitter 4 through a transmitter driving circuit 24 to dispatch ultrasonic waves. If a person 3 is positioned in a predetermined distance from a window comparator 10, the ultrasonic waves are reflected as ultrasonic waves having a particular waveform which are inputted into an ultrasonic receiver 5, and then are inputted through an amplifier 7 to a comparator 8 to compare them with a reference signal. In this case, depending on the presence or absence of the person 3, as the waveforms differ, a prescribed signal is issued from the comparator 8 if there is the person 3, so that a relay 13b is closed, and an alternative current is passed to the heater 2 of the foot warmer. Thus, depending on the presence or absence of the user, the heater is automatically switched on or off to improve the effect of saving of electricity. |
