IOS-DDR-WH Commercial Grade Dual Load In-Wall PIR Occupancy/Vacancy SensorThe passive infrared sensors work by detecting the difference between heat emitted from the human body in motion and the background space. The sensor switch can turn a load ON and hold it as long as the sensor detects occupancy. After no motion is detected for the set time delay, the load turns OFF automatically. The IOS DDR has two relays (equal to Dual Load Switch). Since this device responds to temperature changes, care should be taken when