| 摘要 |
A differential-type fire warning apparatus is provided to cut down the production cost by forming a circuit by using cheap transistors instead of expensive PUTs(Programmable Unijunction Transistor) or SCRs(Silicon Controlled Rectifier). In a differential-type fire warning apparatus, a temperature sensing unit(10) sensing the external temperature change is composed of a first temperature sensor(TH1) protruded from a PCB(Printed Circuit Board) to sense the temperature change of the external air, a second temperature sensor(TH2) closely attached to the PCB to detect the heat of the air ascending from the lower side, slower than the first temperature sensor, two transistors(TR5,TR6), and five resistors(R8-R12). A trigger unit(20) is triggered when the first temperature sensor absorbs the heat. The trigger unit comprises two transistors(TR3,TR4), four resistors(R4-R7), and one capacitor(C3). An LED(Light Emitting Diode) display unit(30) comprises two transistors(TR1,TR2), two resistors(R1,R2), two capacitors(C1,C2), and an LED. The LED display unit displays the warning state in response to the trigger unit.
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