| 摘要 |
Calling circuit, in particular for telephony, containing an isolating capacitor, a limiting resistor and a piezoelectric self-exciting electro-acoustic converter, characterized in that it has, between the serial connection of the isolating capacitor (C) and limiting resistor (R1), and the electro-acoustic converter (SPPE), a Zener diode (D1) connected in parallel with a discharging resistor (R3), as well as, connected in series, a barrier Zener diode (D2) and a regulating resistor (R2).<IMAGE>
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