 The bottom-attack mode is active when the selector switch is set to 4, 10, or 24 hours and the passive infrared sensor (PIRS) trigger cover is in place.The SLAM is equipped with a passive infrared sensor (PIRS) that was specifically developed for the side-attack mode.The PIRS detects trucks and light armored vehicles by sensing the change in background temperature when a vehicle crosses in front of the PIRS port.