The SA series safety seismic switch provides triaxial vibration detection and is viable for protecting vulnerable structures from earthquakes and other vibration events. Depending on the application, the switch incorporates a range of safe shutdown options. The SA-3 model features three high-integrity low-noise piezoelectric seismometers positioned at 90º to each other along with the associated alarm circuitry housed within a weatherproof painted steel enclosure. It is seismically qualified to IEEE-344 and when the signal from any axis exceeds the pre-set alarm level, the alarm relay is activated. The sensors consist of a unique system of matched piezoelectric elements arranged in a ‘reciprocal’ configuration providing a functional test capability. Application of a 1Hz signal to the calibration crystal element mechanically excites the measuring elements resulting in a defined signal output that can be used to perform a full loop check of the seismic switch.