| 摘要 |
A loading dock door (8a,fig.1) system, features sensors, such as two horizontally spaced laser 30a, 30b beams and detectors, 32a, 32b, which count the number of people passing in (A) and out (B) through the open door (8a,fig.1). When the number of people in, and the number of people out are equal, a control unit 14 responds by closing the door (8a,fig.1). The sequential breaking of the two laser beams 30a,30b, provides a person in, and person out, comparable, numerical reading. The system may be aimed at keeping a door closed when it is not in use, thus saving some heat energy leakage from the building. |
