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The difference between the self drive and external drive buzzers
Depend on the driving signal, the buzzer divide into self drive and external drive. However inner circuit/ no circuit, DC/ AC, and active/ passive are all mean the same.

The design of the self drive buzzer is to set the circuit inside the buzzer and just offer the direct current to work. The inner circuit has the designed frequency and voltage for the buzzer to generate sound, therefore the frequency of the self drive buzzer is fixed. However the frequency is still different from each buzzer, normally is 2300Hz, the acceptable range is +/-300Hz.

However, the external drive buzzer needs to be drove by the signal of 1/2 square wave V 0-p (magnetic type), or square wave V p-p (piezo buzzer)

It is convenient to use a self drive buzzer, but the disadvantages are the higher cost, the higher defective rate and the unchangeable frequency.

The comparison between self and external drive buzzer:

依照驅動信號的不同,蜂鳴器分為自激式及他激式二類,有很多不同說法,但指的都是這二種分類,

如:內含(不含)線路,直流DC/交流AC Type, 有源(無源),

自激式的蜂鳴器是將驅動線路直接設計到蜂鳴器中,故只需給予直流電壓,

內含的驅動線路,就會產生設計好的頻率及電壓給蜂鳴器發聲,所以自激式的頻率是固定的.

但每顆蜂鳴器間的頻率仍會有些差異,一般常見的是2300Hz, 頻率上下300Hz都算可接受的範圍,

而他激的蜂鳴器,需由外部線路給予1/2方波V 0-p(電磁式),或方波Vp-p(壓電式)的信號,才會發聲,

在使用上用自激式的蜂鳴器有其方便的地方,但因為成本及不良率較高,且頻率不可調整,