Simple buzzer circuit 4b

It can produce unusual-pitched sounds and can be used in various sound simulators and sound
alarms. The transistors
    VTi and VT2 form a multivibrator, and VT3 forms a power amplifier.     The tone emitted by the sounder can be adjusted through the potentiometer RP and the capacity of the selection capacitor Ct. For example, when Cl is 500VF, the sound signal can change at a speed of about 500 Hz/s in the range of 300-3000Hz. The frequency changes smoothly.