Murata's PKM family of self-drive piezoelectric sounders feature a three-element internal piezo diaphragm for generation of a single (fixed-tone) audio signal. An external drive circuit which utilizes the 3-element diaphragm as the frequency-determining component is required. A type 2N3904 NPN transistor or equivalent can serve as a suitable active device for the drive circuit. Supply voltages from 3.0 to 20.0Vdc are acceptable, and SPL (Sound Pressure Level) of 75-90 dB @ 10cm using a 12Vdc supply is typical. All products are RoHS compliant.