| 摘要 |
PROBLEM TO BE SOLVED: To read/write data outputting an optimal modulated signal to each of IC cards, which can be accessed with respectively different amplitude transit modulated signals. SOLUTION: A modulation circuit 12 for a card reader/writer is provided with drivers DRV1 and DRV2, an F/F circuit 41, an AND circuit AND inverters INV1 and INV2, to which different power supply voltages are impressed. When a switching signal (b) is L, the driver DRV2 is controlled into high impedance and the driver DRV1 is controlled into carrier output state and high impedance corresponding to H/L of a transmitting code (a) so that the modulated signal of modulation factor 100% can be outputted. When the switching signal (b) is H, on the other hand, the driver DRV1 is controlled into carrier output state and high impedance corresponding to H/L of the transmitting code (a) and the driver DRV2 is controlled into high impedance and carrier output state so that the modulated signal of modulation factor 100% can be outputted. |
