Importance

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Abstract

An IC card, as a portable medium, has an oscillator for generating a low-frequency clock signal for time-piece. A display clock for display is provided for counting the clock signal. The time based on a count carried out by the display clock is displayed on the IC card a display section. In this case, the count of the display clock can be changed, as appropriate, by using keys on the keyboard provided on the IC card. The IC card also incorporates a transaction clock for counting the clock signal. The count carried out by this transaction clock is used to indicate the standard time. A count carried out by the transaction clock cannot be altered by use of the keys of the keyboard. The clock for time display may be the transaction clock allowing an access of the keyboard. The time for setting a term of validity and the key for encoding may be provided by the transaction clock rejecting an access by the keyboard and providing the time equal to that of other cards.

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First Claim