| 摘要 |
A system that provides notice of a lost signal. A wireless device and a control device employ radio frequency identification (RFID) technology, which uses radio frequency signals to communicate with one another via communication link having a reception range. The control device transmits a signal to the wireless device via the communication link. The wireless device responds by transmitting a return signal via the communication link. The control device processes the return signal to determine if the wireless device is within the reception range, if not, the control device provides an audible, written or visual alarm. |
