Importance

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Abstract

An improved system is disclosed for detecting invalid transaction cards at remote transaction terminals. The system includes providing each terminal with a master table having data corresponding to invalid cards. The data in the master table is less than the actual account numbers of the invalid cards. By using a compressed version of the data, the file can be shortened to facilitate storage and transmission. The compressed data file is arranged such that when an invalid card is presented, it will be identified and routed on for further processing. In the preferred embodiment, the probability that a valid card will be identified as potentially invalid is on the order of one to three percent. During each transaction, the master table is supplemented with information about the account number of the transaction card presented for the purchase. In this manner, any subsequent use of the card will be routed for additional processing. A scheme for compensating for data transmission errors is used to reduce the possibility that information about invalid cards is not lost when the master file is distributed.

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First Claim