AST SMT Transducers Mallory Sonalert AST SMT Transducers offer a 73dBA to 90dBA sound pressure range, up to 6000Hz frequency, and 1.5V to 12V voltage range. AST series transducers feature a 73dBA to 90dBA sound pressure level range, 110mA maximum current rating, and a diameter up to 17.5mm. Mallory Sonalert AST SMT Transducers are RoHS compliant.