To carry on the calling service with no insertion of a new card even when the remaining frequency of a using card expires during the calling service by providing a means which can add new value information to a card in response to an information addition request that is given to the card during the supply of service and also can liquidate the added value information.
The decision of a recharge request shows 'Y' when the remaining frequency of an IC card 3 expires during a call with a public telephone set 1 at which the call has been started and then the recharge request is given from the telephone set 1 after a user ID is operated via the telephone set 1. Under such conditions, a control part decides whether the recharge is OK according to the user ID that is given in response to the recharge request. When the recharge is OK, the prescribed recharge frequency is stored in an area of a storage corresponding to the received user ID. At the same time, the control part transmits the recharge frequency to the telephone set 1 to record it on the card 3.
SAITO RYUICHI
SAGARA KAZUHIKO
NIPPON TELEGRAPH & TELEPHONE
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