The 24 VDC ultrasonic sensors utilize advanced, omni-directional, Doppler technology to sense occupancy. When an ultrasonic sensor detectsmovement in a controlled area, it switches lighting on through a Watt Stopper power or auxiliary pack. The sensor controls the power pack through low voltage wiring. Once the area is vacated and theuser-adjustable time delay (15 seconds to 15 minutes) has elapsed, lighting systems automatically switch off.