| 摘要 |
<p>A beam of light (14) is caused to scan a room, creating light pulses as it strikes retroreflective elements (12) strategically placed in the area to be protected. This spatial pattern of pulses is detected and compared to a standard pattern. The absence of a pulse is used to indicate the presence of an intruder or a missing article. An unexpected pulse is used to indicate an open door, drawer, window, etc. The machine (10) may be easily taught a new standard pattern, allowing the same device to be used in a wide variety of applications.</p> |
