| 摘要 |
An ultraloud ambient condition detector incorporates a sensor in combination with a control circuit. An alarm indicating signal from the control circuit energizes a multi-frequency drive circuit which produces a band of output frequencies usable to drive a piezoelectric output element. The output element has one or more resonant frequencies which fall within the band of the drive frequencies. A feedback circuit is provided to maintain the unit in an alarm state, after it has switched into that state, even if the input ambient condition indicator signals a decline in the value of the sensed ambient condition or in the presence of noise perhaps generated by the audio output device. A high current, low duty cycle battery test current repetitively loads the battery consistent with current load when the detector is in an alarm state.
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