| 摘要 |
<p>The alarm signal is delivered when the object or person has moved beyond a permissible distance from its destination. A signal is sent and received between the destination and the movable object or person. Its range corresponds to the permissible distance, and a warning, alarm or safety device is released when the signal is no longer received. The receiver may be fitted to a collar worn by a guard dog. A high pitched whistle is sounded recalling the dog when it wanders too far away. The whistle may be sounded when a valuable object is removed.</p> |
