Simple distinguishing method between active buzzer and passive buzzer？ The fundamental difference between External Drive buzzer and Internal Drive buzzer is that products have different requirements for input signals; The ideal signal of active buzzer is DC, which is usually marked as VDC, VDD, etc. Because there is a simple oscillation circuit inside the Piezzo Buzzer, which can convert the constant DC into a pulse signal of a certain frequency, so as to realize the alternating magnetic field and drive the vibration and pronunciation of aluminum sheet. However, some piezo sounder can also work under specific AC signals, but they have high requirements for the voltage and frequency of AC signals, which is generally not used. piezo transducer has no internal drive circuit. Some companies and factories call it Transducer Indicator Sounder, which is called sounder in the international standard. The ideal signal square wave of passive buzzer. If a DC signal is given, the Audio Devices will not respond, because the magnetic circuit is constant and the molybdenum sheet cannot vibrate and sound. if you have more questions,please contact FBelec's engineer!!