| 摘要 |
<p>Whenever power fails, an audio signal is produced by an oscilla?or, which includes a pair of transistors of opposite conductivity having the collector of each connected to the base of the other and is maintained in an off condition as long as the power is on. When the oscillator is turned on, a rapidly changing surge of current is supplied from a battery, which has a capacitor in parallel therewith, to an audio producing device in the discharge path of the oscillator. This surge of current is produced through utilizing a Zener diode between the battery and one of the two transistors of the oscillator. The parallel combination of a resistor and a capacitor is disposed between the Zener diode and the transistors of the oscillator. A resistor also is disposed between the emitter of the transistor initially turned on and a capacitor, which is charged to a potential to turn on the transistor. This resistor is of substantially lower impedance than a resistor between the capacitor and the battery. This arrangement increases the power at least two orders of magnitude.</p> |
