To provide a detector which detects the dynamic change and static state of an object to be detected by outputting a detection signal upon detecting the dynamic change of the object within a fixed detection range and another detection signal upon detecting the presence of the object within a different detection range in the fixed detecting extent, and then, combining both signals.

When a man enters a lavatory, a pyroelectric infrared sensor 11 catches the dynamic change of the man within the detection range of the sensor 11 and brings the output (b) of a processor circuit 12 to an H level. When the man stands in front of a mirror at the center of the lavatory, a range finding sensor 13 catches the man within a detection range narrower than the detection range of the sensor 11 and brings the output (a) of a processing circuit 14 to an H level. A control circuit 15 makes the sensor 11 detectable the small movement of the man, such as the movement of the hand, etc., by narrowing the detection range of the sensor 11 by zooming the sensor 11 by zooming in a zooming mechanism 16 in accordance with a distance signal from the circuit 14. When the man moves from the detection range of the sensor 13, the output (a) of the circuit 14 goes to an L level and the circuit 15 zooms out the zooming mechanism 16 with an output (c). When the man gets out of the detection range of the sensor 11 going out the lavatory, the output (b) of the circuit 12 goes to an L level. While the man stays in the lavatory, the output (d) of a synthesizing circuit 17 becomes an L level and a detector can be turned on automatically.