| 摘要 |
PURPOSE:To easily decide whether a voltage is higher than a set value or not by placing a Schmitt circuit in inverting operation by utilizing the steep part of breakdown characteristics of a lamda diode, and turning on a light emitting diode. CONSTITUTION:A variable resistance 4 for adjusting a voltage from a DC power source 6 and the lamda diode 5 which has breakdown characteristics are provided between an output terminal of the DC power source 6 and the signal input terminal of the Schmitt circuit and the output signal of the Schmitt circuit is displayed by using light emitting diodes (LED) 9 and 10. Then, when the source voltage is higher than a voltage set by the variable resistance, the lamda diode 5 is cut off, so the transistor (TR) 7 of the Schmitt circuit is off and the LED 9 is off. When the TR 7 is off, a TR 8 is on and the LED 10 illuminates. Further, when the source voltage drops below the set voltage, the lamda diode 5 turns on and the TR 7, therefore, turns on, so the LED 9 emits light. Consequently, the TR 8 turns off and the LED 10 does not illuminate.
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