The sensor detects changes in the infrared energy given off by occupants as they move within the field-of-view. When occupancy is detected, a relay located within the power pack is signaled to switch the line voltage lighting load on. The sensor is powered with 15 VDC provided from the power pack. An internal timer, factory set at 30 seconds, keeps the lights on during brief periods of no activity. This timer is push-button programmable, and is reset every time occupancy is re-detected. This state-of-the-art design requires no manual field adjustments. To assist with scheduling relamping, the sensor has a built-in lamp runtime counter and switch counter, both of which can be read out via the units LED.