How does Eco sensor of BL2201PT work?

ECO sensor detects users' presence in front of the monitor within the set range. If the sensor detects no presence, the monitor is turned off in 40 seconds to save power. If the monitor is turned off by the ECO sensor, the power button flashes in green. If the ECO sensor detect no presence for over 2 hours, the monitor will be powered off. Press the power button to turn on the monitor.