| 摘要 |
A perimeter monitoring system is arranged to detect passage across a perimeter of an area. The system primarily includes an emitter (120), a retroreflector (116), a detector (122) and an alarm (146). The emitter (120) provides a modulated visible laser beam (115). The retroreflector is arranged to direct the beam along a segment of the perimeter and return the beam along the segment. The detector (122) includes a device (208) that blocks reception of light outside an angle of less than 5 degrees. One or more local or remote alarms (162) are activated in response to the signal. For example, a remote alarm is located on the inside of a residence window where it is activated by another visible laser beam. Alignment of the peripheral monitoring system is less costly and false alarms are less likely than with known system.
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