Acoustic call signal generator for telephone - has moving coil or piezoelectric transducer and oscillating circuit consisting of triggering diode and capacitor

摘要

Calling signal is generated by an oscillating circuit and converted into an audible signal by an electroacoustical transducer. The transducer consists of a moving coil transducer (WD), and the oscillating circuit of a triggering diode (D) in series with the transducer (WD), and of a capacitor (C) between the telephone line wires (a, b) in parallel with the series circuit of the diode and transducer (D/DW). In parallel with the transducer (WD) there are series connected fixed (RZ) and variable (R3) resistances. The transducer (WD) may alternatively be a piezoelectric device.