| 摘要 |
PROBLEM TO BE SOLVED: To prevent the mutual interference even among plural pieces of reader/ writer which are placed close to each other by adding an interference level detection means and a mode switch means to every reader-writer. SOLUTION: A reader-writer 1 consists of a read-write control part 2, a modulation part 3, an amplifier part 4, a transmitting antenna coil 5, a receiving antenna coil 6, an amplifier part 7, a detection part 8 and an A/D converter 9. The part 2 has an interference level detection means 2a and a mode switch means 2b. The means 2a can detect an interference level after the lapse of a fixed time in an interference detection mode. The means 2b performs the switching between the interference detection mode where the interference level is detected by the means 2a and a communication mode where the data communication is carried out between the transmitting and receiving parts. Then the means 2b sets a communication mode when no interference level is detected by the means 2a and then sets an interference detection mode after the communication mode is over. |
