Abstract: A device responsive to infrared radiation can control a current line to such items as interior lighting or room air conditioners in order to activate these items in response to the presence or absence of a person within their service area. The device includes an infrared detector comprised of a thermopile formed by thin-film techniques for producing detection signals amplified by a series of amplifier stages having filters passing only signals corresponding to motion of a human body. The amplified signals are led to the reset port of a timing circuit which will open the current line when no human motion is sensed within a predetermined time period. Further, the housing for the device includes a protruding neck portion carrying the infrared detector and adapted to be held by a retaining nut after insertion through a ceiling unit or the like.