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Transaction approval system

  • US 4,822,985 A
  • Filed: 01/06/1987
  • Issued: 04/18/1989
  • Est. Priority Date: 01/06/1987
  • Status: Expired due to Term
First Claim
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1. In a transaction network including a central processor, a plurality of transaction terminals and a plurality of transaction cards, each card having an account number associated therewith, a method for identifying invalid cards comprising the steps of:

  • (a) generating a master table at said central processor, said table including at least a first bit map B bits in length;

    (b) selecting a set of digits from the account number of a first invalid transaction card;

    (c) calculating a first index value which is an algorithmic function of said set of digits, said first index value being between zero and B-1;

    (d) placing an indicator within said first bit map corresponding to said first index value;

    (e) repeating steps b though d for each invalid card; and

    (f) supplying the master table to each transaction terminal whereby during a transaction, the transaction terminal determines if an indicator exists in the master table corresponding to the account number of the card presented for the transaction.

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