| 摘要 |
PURPOSE:To enable closing of a power source for a fan and a power source for an alarming device, by a method wherein the terminal voltage of a temperature sensor, formed by a thermistor situated in the vicinity of a mantle piece, produces a comparison voltage, and a plurality of comparators are set according to a necessary heating temperature and a maximum safe temperature. CONSTITUTION:A temperature sensor 4 is connected in parallel to a resistor 5 while acts as a resistor for a partial voltage together with a resistor 6. The partial voltage produces a comparison voltage. When the temperature in a mantle piece is not increased to a necessary heating temperature, an output from a comparator 9 is H, but when exceeding the necessary heating tempera ture, an output is decreased to L. With a transistor 11 turned ON, a fan 14 starts rotation by means of an AC source 1 serving as a power source. when the temperature in the mantel piece is not increased to a maximum safe tempera ture, an output from a comparator 16 is H, but when exceeding the maximum safe temperature, an output is decreased to L. Thus, a transistor 19 at a next stage is turned ON. With the transistor turned ON, an alarming display device, for example, an alarm 20, is actuated by means of an AC source 1 serving as a power source.
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