Buzzer is divided into two kinds of active and passive, active refers to its internal multi-vibrator and other structures, the external only need to provide voltage, you can send a fixed frequency sound. Passive means that there is no internal oscillator source, the need for external circuits to provide a certain frequency of the drive signal.

Precautions:

① For passive buzzer, take a diode in parallel to protect it to absorb the electromagnetic coil, resulting in anti exciting spikes, which may lead to high frequency interference of system power and signal lines.

② in the microcontroller applications, there are many buzzer reuse. Usually in the drive circuit plus capacitor isolated DC signal, you can reuse. But pay attention to the software design, to avoid interference.