| 摘要 |
A detection system includes one or more base stations and one or more sensors. The base station defines a detection area and is configured to transmit a detection signal at a first frequency. The base station is further configured to facilitate selective variation of the detection area. The sensor is configured to detect the detection signal and transmit a communication signal at a second frequency in response to the detection signal. Movement of the sensor between the detection area and an area outside of the detection area affects detection of the detection signal. The first frequency is less than the second frequency.
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