| 摘要 |
PROBLEM TO BE SOLVED: To perform optimum impedance matching with a non-contact IC card connected by radio. SOLUTION: When there is one IC card connected by radio, an input voltage at such a time is set as the reference voltage of a comparator CM in a voltage comparator 15. Then, a matching circuit 12A is selected. When one IC card is connected by radio and the matching circuit 12A is selected, impedance matching is performed between an IC card reader 1 and the IC card connected with this reader by radio and the input voltage of the comparator CM is lower than the reference voltage. When two IC cards 2A and 2B are connected by radio, however, impedance mismatching occurs between the IC card reader 1 and the respective cards and the input voltage of the comparator CM is higher than the reference voltage. In this case, the comparator CM outputs a switching instruction signal to a matching circuit selector 14 and a matching circuit 12B is selected. |
