| 摘要 |
An intrusion or movement detector including an oscillator for generating a radio signal, an antenna for transmitting said radio signal into an area to be surveyed by said detector, said antenna exhibiting a variable radiation resistance relative to the position and movement of objects in the area to be surveyed resulting in a variable loading on said generator when in use, a monitor for monitoring said variable loading and activating a signal or alarm when said variations in loading reach a predetermined threshold level to indicate an intrusion or movement in the area surveyed.
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