| 摘要 |
<p>A modulated electromagnetic field is established in a designated area to exclude animals from that area. A receiver (18) carried by the animals compares the received modulated electromagnetic field signal level with a pair of predetermined levels (68, 70). A warning (100) is provided if the signal level surpasses the first predetermined level (68) and a control indication (114, 116) is given if it surpasses the second predetermined level (70) to discourage entry into the designated area.</p> |
