In the past used the warning component was mainly the piezo buzzer. Although this kind of sounding body is moderately-priced, but because sends out the sound depending on the electronic contact attack metal, therefore the electronic contact attrition definitely has decided alarm's life, the continuous working life has about generally 50 hours. In addition also has problems and so on corrosion, its use receives the very big limit. Along with the integrated circuit, large scale integrated circuit's development, the electronic device also requests the miniaturization, the high scale, multi-purpose. Therefore has developed the electronic buzzer. The electronic buzzer's characteristic is the volume small, the weight light, the build thin, the power loss is small, does not have the noise, the long life, high reliable moreover the timbre is good, thus obtained the rapid development and the widespread application. The warning component may divide into the autoexcitation and the separate excitation.