| 摘要 |
Concurrent two-way data transfer can be conducted with higher reliability and improved accuracy with an IC card and a reader/writer device kept out of physical contact with each other. A first signal wave is produced by the reader/writer device to transmit first bit information. This first signal wave has trigger pulses at a period T (at the start of a period T), and bit pulses behind the associated trigger pulses by a time interval t1+d. The bit information is represented by the presence and absence of bit pulse, and the presence of a bit pulse is "1", the absence of a bit pulse being "0". The IC card produces a second signal wave to transmit second bit information. The second signal wave is entrained on a set carrier which is transmitted to the IC card through coils. The IC card changes an input impedance of the receiving coil, based on the second signal wave. Resultantly a modulated wave is transmitted between the coils.
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