| 摘要 |
A low voltage warning apparatus is adapted to energize a low voltage indicator in response to a test voltage signal falling below the magnitude of a reference voltage signal. The test voltage signal and reference voltage signal are connected to be received by a comparator circuit so that the comparator circuit output is connected to ground when the test voltage falls below the value of the reference voltage. The low voltage indicator is connected between an indicator power supply and the comparator output so that when the comparator output is connected to ground, a low voltage indicator energizing current flows through the low voltage indicator to provide the desired low voltage indication. In the preferred form of the invention, the low voltage warning apparatus is adapted to receive an AC voltage signal through an ordinary household electrical outlet and includes a rectifier for converting the AC voltage signal into the voltage to be sensed, the voltage to be sensed being a DC voltage signal having a magnitude substantially equal to the amplitude of the received AC signal. The test voltage is held proportional to the magnitude of the DC signal to be sensed, and the reference voltage is derived from a limited and substantially constant voltage signal produced from the voltage to be sensed. The low voltage indicator is preferably energized through the reduced constant voltage signal.
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