The ODS15-ID uses passive infrared (PIR) detection technology to monitor a room for occupancy through a segmented fresnel lens. This specialized lens divides the field-of-view into sensor zones. When a person passes into or out of a sensor zone, the sensor detects motion and switches the lights ON. The lights will remain ON as long as there is an occupant moving through the sensor zones. A delayed-off time adjustment prevents the lights from switching off when the space is occupied. In order to keep the lights-on, a person must pass through a sensor zone at least once during the selected delayed-off time interval. An LED indicator blinks each time the unit detects activity in the sensor zones. When the space being monitored by the sensor is unoccupied for the length of time chosen as the delayed-off interval, the unit will beep 3 times. Ten seconds after the last warning beep, the unit will switch the lights OFF.