| 摘要 |
PROBLEM TO BE SOLVED: To efficiently execute individual recognition of plural IC cards by permitting a reader/writer to change the number of time slots, so that the number of collisions is reduced according to the number of collision on return signals from the respective IC cards in the respective time slots. SOLUTION: A single reader/writer RW executes communication with six IC cards A-F in a communication enable area Area by using plural time slots. The time slot number change means of the reader/writer RW recognizes the number of the collisions of return signals from the IC cards A-F in the time slots. When the recognized number of collisions is large, the number of time slots is increased. When the recognized number of collisions is small, the number of time slots is reduced. The time slot number change means changes the number of time slots according to the number of collisions on the communication with the IC card, and therefore the plural IC cards A-F can be recognized efficiently and individually. |
