MSR205 Piezoelectric Indicators Mallory Sonalert MSR Series is a Piezoelectric Indicator, with DC voltage, housed in a ø23mm x 11mm blue round housing with PC Pins. Features include loud continuous or pulse sound levels ranging from 75dBa to 96dBa and a 3.4kHz to 3.9kHz frequency range with gullwing lead or solder pin terminations. Options include board mount or flush mount and sealed (wash label included) versions are also available.