| 摘要 |
An electronic timer having an oscillator, a counter which counts outputs of the oscillator up to a predetermined count value and thereupon generates an output, and an output circuit for generating an output signal in response to the output from the counter, the oscillator comprising a first terminal for connection with a time constant circuit consisting of a resistor and a capacitor, a second terminal supplied with a reference voltage, a dividing resistance circuit for developing a first upper limit voltage and a lower limit voltage, a first upper limit comparator for comparing a potential at the first terminal with the first upper limit voltage, a second upper limit comparator for comparing the potential at first terminal with the reference voltage, an OR-circuit for receiving outputs from the first and second upper limit comparators, a lower limit comparator for comparing the potential at the first terminal with the lower limit voltage, a flip-flop which is set by an output from the OR-circuit and reset by an output from the lower limit comparator, and a transistor for discharging the capacitor in response to an output generated from the flip-flop.
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