| 摘要 |
<p>The device (21) comprises a piezoelectric transducer (22), a battery (23) and a circuit which applies a control voltage to this transducer (22) or which short circuits it depending on the state of a control signal (Sc). This control voltage is produced by a voltage raiser comprising a coil (25), a diode (26) and a capacitor consisting of the transducer (22), which are connected up in series in this order between the terminals of the battery (23), and an oscillator (28) responding to the control signal (Sc) in order to control a transistor (27) so that it alternately establishes and removes a short circuit across the terminals of the circuit formed by the diode (26) and the transducer (22) or so that it is permanently off. A second transistor (22) likewise responds to the control signal (Sc) in order to short circuit the transducer (22) when the first transistor (27) is off. This device (21) is simpler, cheaper and consumes less electrical power than the known devices. <IMAGE></p> |
