| 摘要 |
<p>The motion detector of the present invention, together with associated AG switching circuitry (17) form a lighting control system which turns on room lights when the room is occupied, and extinguishes the lights when unoccupied. The detector sensitivity or threshold is adjusted (by 18, 18A or 18B) in response to the previously detected conditions, providing reliable indication of both entry and continued presence in the controlled area, and producing few false alarms. Two threshold levels of detection are provided, the higher level being used to detect initial entry into the room. After entry is detected, the motion detector lowers the threshold to detect the weaker signals usually occurring for continued presence in the area of the detector. When the occupant leaves the area, the motion detector threshold or sensitivity returns to the original value after a timeout period.</p> |
