PURPOSE: To miniaturize the bell signal generating circuit by providing a photocoupler for the DC insulation of pulse signals and a power supply part for insulatively forming power supplied to a differential amplifier or the like with high frequency power.

CONSTITUTION: When a pulse signal Po is supplied from a bell signal generating circuit 20 to a photocoupler 24, the DC insulated pulse signal is generated at a gap to a resistor 26, sent to a voltage follower amplifier 28, amplified and outputted as a pulse signal P2. The signal P2 is supplied to a low-pass filter 29, the higher harmonic wave component is removed, and the signal is turned to a sine wave signal P3. The DC component of signal P3 is removed by a capacitor 30, and the AC component is supplied to an inverter amplifier 31. When the resistance is set on specified conditions at the amplifier 31, the gain is decided, and the signal is turned to an output signal P4, inversely converted by an inverter amplifier 32 and turned to an output signal P5. When the signals P4 and P5 are respectively set at 113Vp-p in this case, an output signal is turned to 226Vp-p(=80Vrms.). When a DC voltage at -48V is superimposed to this output signal, a bell output is provided.