| 摘要 |
A reader/writer (R/W) transmits a query command ALL (A), which causes RFID tags (A) with a communication method (A) to respond at a time, to N RFID tags (A) with the communication method (A) and X RFID tags (C) with a communication method (C). In this case, since R/W receives responses from N RFID tags (A), it can recognize presence of the RFID tags with a communication method (A) from its reception level or the like. Next, R/W transmits a query command ALL (B) which causes RFID tags (B) with a communication method (B) to respond at a time. In this case, since R/W receives no response, it can recognize that no RFID tag with the communication method (B) is present rapidly. In an RFID system, therefore, a communication time between RFID tags and an RFID reader/writer can be reduced.
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