The piezoelectric ceramic buzzer has a simple structure in which a ceramic piezo-element is glued to a vibration plate. The piezoceramic element expands or shrinks diametrically when an alternating voltage is applied. This characteristic is used to bend the vibration plate, which generates sound. The acoustic generating method can be subdivided roughly into the self-drive oscillation method and the external drive oscillation method. The former yields the lowest impedance on the acoustic generator and produces sound through the oscillator circuit's positive feedback. This allows the creation of sound pressure using a simple circuit. The external drive oscillation method uses a fixed frequency and produces sound through the oscillator.
Specifications:

1. tone type: external drive
2. operating voltage: 3-28Vac
3. rated voltage: 5Vac
4. current consumption: 1.5mA
5. resonant frequency: 4.0 ± 0.5kHz
6. sound pressure level: 85dB
7. connector type: leads
8. body colour: black
9. weight: 4g