Abstract: The number of persons or objects entering and leaving a space such as a room are accurately counted in response to a bidirectional detector unit through which a person or object must completely pass to register a count, and means are provided to disregard any change in the detector unit unless the person or object goes completely past the bidirectional detector, said counting means being connected to a structure whereby when the space is indicated to be completely unoccupied the illumination of the space and/or the temperature modification of the space will be automatically extinguished or modified to more economical levels.