| 摘要 |
<p>A piezo-electric signalling device has an oscillator circuit which includes a transistor amplifier and a piezo-electric transducer (10). There is a Zener diode (30) in the transistor circuit (20). The Zener voltage of the diode determines the start-up voltage of the device. By choosing diodes with different Zener voltages, the start-up voltage may be preselected. In other embodiments, the diode may be connected in the base circuit of the transistor or in other portions of the oscillator circuit.</p> |
