| 摘要 |
<p>In combination with article theft detection apparatus which employs a signal generator coupled to an antenna at a checkpoint and means for detecting and indicating the change in signal energy caused by the presence of a resonant circuit tuned to the signal frequency adjacent the antenna, a second antenna adjacent the checkpoint, a second detecting system connected thereto and means controlled by the second detecting system for disabling the indicating means when the energy change is due to spurious radiation, line voltage changes, etc., or due to the presence of such a resonant circuit at a different checkpoint to prevent false or ambiguous indications.</p> |
