| 摘要 |
A system for keeping account of predetermined homogeneous units by means of an article such as a card, carrying information which may be the amount of a credit balance, and an external device for operating on the information. In general, the balance on the card is initially validated. Thereafter, the balance is irrevocably drawn upon as desired until a zero balance is reached. In order to avoid a single large expenditure to validate the card, and at the same time to minimize the possibility of fraud, a memory in the card has a plurality of zones which are individually validatable. A separate validating field in the memory has validating bits corresponding to individual memory zones. The validity field is accessible by the external device only, and is protected by a coded key embodied in the card. To make the system usable for recording other than whole numbers of units, one of the zones may have a plurality of sub-zones. One of the sub-zones may be allocated to multiples or sub-multiples of individual units. |
