mini electronic buzzer 1.over 30min continuous working 2.low power consumption 3.very good tone quality 4.long life mini electronic buzzer ModelVoltageFrequency(Hz)installation modesDb(A)/mSTBNAC110V50Hzsurface85~95AC220V50Hzsurface85~95AC380V50Hzsurface85~95DC12V50Hzsurface85~95DC24V50Hzsurface85~95 mini electronic buzzer