a plumbing device uses electronic control circuitry with two infrared emitters and one infrared receiver to detect objects in a particular region of space . in one embodiment , detection of an object using both sensors results in the plumbing device turning on . when no object has been detected for a certain amount of time , the plumbing device is turned off . also , when the plumbing device has run for another certain amount of time , the plumbing device is turned off regardless of whether an object is still being detected . in another embodiment , the output of the ir emitters is partially blocked by one or more mask elements to tailor the region that is covered by both ir emitters and , hence , the region that triggers the opening of the plumbing device valve .