摘要 |
An alarm system includes a number of radio frequency identification (RFID) tags, an RFID reader, a warning unit, and a control module. The RFID reader receives radio-frequency signals from some of the number of the RFID tags via an antenna when the some of the number of the RFID tags are in a determined area around the RFID reader. The control module activates the warning unit when a radio-frequency signal from at least one of the number of RFID tags is not received by the RFID reader.
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