SILENCER ALA90 Mini Electromagnetic Dual Zone Shock Sensor An impact sensor is very important to all security systems. You need to have the alarm triggered if a thief makes an impact trying to shatter your car window. The ALA90 is the perfect sensor for this application. It is small and compact so it fits under your dash nicely. Using a fluctuating magnetic field technology it is able to discern the difference between the neighbors ball bumping your car or a would be thief breaking the window. The AlA90 has this pre-warning feature to avoid false alarms. The Silencer ALA90 has a 4 pin connector that plugs into the main module of Silencer, Carbine, Marksman and PL Series alarms. See the attached