Transaction approval system

• US 4,908,521 A
• Filed: 01/10/1989
• Issued: 03/13/1990
• Est. Priority Date: 01/06/1987
• Status: Expired due to Term

• Current Assignee: Visa International Service Association (Visa, Inc.)
• Original Assignee: Visa International Service Association (Visa, Inc.)
• Inventors: Campbell, Carl M., Boggan, Elvis W.
• Primary Examiner(s): Envall, Jr., Roy N.
• Application Number:
  US07/295,662
• Time in Patent Office: 427 Days
• Field of Search: 235/380, 235/382, 235/382.5, 235/379, 380/24
• US Class Current: 235/380
• CPC Class Codes: G06Q 20/403 Solvency checks
• CPC Class Codes: G07F 7/08 by coded identity card or credit card or other personal identification means without personal verification means G07F7/02

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.

Claims

1. A method for compensating for transmission errors in a data file wherein said file includes information relating to a list of transaction cards and wherein each listed card is represented by at least one indicator comprising the step of:

placing an indicator at each location in the data file where a transmission error may have occurred such that information about the listed cards will not be lost.

2. A method of operating a transaction terminal for facilitating the off-line approval of transactions based upon the use of transaction cards each having an account number, comprising the steps of:

receiving information about a list of transaction cards in the form of a master table wherein each listed card is represented by at least one indicator;

detecting transmission errors; and

compensating for any ambiguous errors by placing an indicator in the table in each of the locations where a transmission error may have occurred so that information about listed cards will not be lost.

3. A method as recited in claim 2 wherein said master table is arranged in blocks of data, each block consisting of a plurality of bytes, wherein each byte includes a parity check bit and wherein each block further includes a longitudinal redundancy check byte generated by exclusive-or-ing the other bytes in the block and further including the steps of:

exclusive-or-ing all of the bytes in each block to generate a block error byte and recording the number of errors based on the contents of the block error byte; and

determining how many and which bytes have a parity error based on the parity check bit.

4. A method as recited in claim 3 further including the steps of:

determining if the number of parity errors in a block equals the number of errors in the associated block error byte and if that number is greater than one, and if so, then;

inserting indicators in each byte shown to have a parity error, said indicators being inserted at bit locations shown to have errors based on the contents of said block error byte.

5. A method as recited in claim 4 wherein said step of inserting indicators is performed by or-ing the block error byte with each byte in the block with a parity error.

6. A method as recited in claim 3 further including the steps of:

determining if the number of parity errors in a block is greater than the number of errors indicated by the associated block error byte, and if so, then;

inserting indicators into all of the bits of any bytes that has a parity error.

7. A method as recited in claim 3 further including the steps of:

determining if the number of parity errors in a block is less than the number of errors indicated by the associated block error byte, an if so, then;

inserting indicators in all of the bytes in the block at the bit locations shown to have errors based on the contents of the block error byte.

8. A method as recited in claim 7 wherein said step of inserting indicators is performed by or-ing the block error byte with all of the bytes in the block.

9. A method of operating a transaction terminal for facilitating the off-line approval of transactions based upon the use of transaction cards each having an account number, comprising the steps of:

receiving information about a list of transaction cards in the form of a master table, said master table being defined by a plurality of bit maps and wherein each listed card is represented by one indicator in each bit map;

detecting transmission errors; and

compensating for any ambiguous errors by placing an indicator in the table in each of the locations where a transmission error may have occurred so that information about listed cards will not be lost.

10. In a transaction network including a central processor, a plurality of remote transaction terminals and a plurality of transaction cards, each card having an account number associated therewith, a method for facilitating off-line approval of transactions comprising the steps of:

generating, at said central processor, a master table containing data derived from a list of transaction cards, said data being less than the entire account number of each card and wherein each listed card is represented by at least one indicator;

distributing the master table in a manner to be locally accessed by the remote transaction terminals;

detecting transmission errors and placing an indicator in locations in the master table which are possibly in error; and

comparing the account number of a transaction card being presented for a pending transaction with the data in the master table and generating an output signal based on the outcome of that comparison.

11. In a transaction network including a central processor, a plurality of remote transaction terminals and a plurality of transaction cards, each card having an account number associated therewith, a method for facilitating off-line approval of transactions comprising the steps of:

generating, at said central processor, a master table containing data derived from a list of transaction cards, said master table being defined by a plurality of bit maps wherein each listed card is represented by one indicator in each bit map;

distributing the master table in a manner to be locally accessed by the transaction terminals;

detecting transmission errors and placing an indicator in locations in the master table which are possibly in error; and

comparing the account number of a transaction card being presented for a pending transaction with the data in the master table and generating an output signal based on the outcome of that comparison.

12. An apparatus for compensating for transmission errors in a data file wherein said file includes information relating to a list of transaction cards and wherein each listed card is represented by at least one indicator comprising:

storage means for holding said data file;

means for detecting transmission errors; and

means for placing an indicator at each location in the data file where a transmission error may have occurred such that information about the listed cards will not be lost.

13. A transaction terminal for facilitating the off-line approval of transactions based upon the use of transaction cards each having an account number, comprising:

storage means for holding a transmitted data file containing information about a list of transaction cards in the form of a master table wherein each listed card is represented by at least one indicator; and

processor means, said processor means for detecting transmission errors, said processor means also for compensating for any ambiguous errors by placing an indicator in the table in each of the locations where a transmission error may have occurred so that information about listed cards will not be lost.

14. An apparatus as recited in claim 13 wherein said master table is arranged in blocks of data, each block consisting of a plurality of bytes, and wherein each byte includes a parity check bit and wherein each block further includes a longitudinal redundancy check byte generated by exclusive-or-ing the other bytes in the block and wherein said processor further functions to exclusive-or all of the bytes in each block to generate a block error byte and thereafter recording the number of errors based on the contents of the block error byte, said processor means further functioning to determine how many and which bytes have a parity error based on the parity check bit.

15. A terminal as recited in claim 14 wherein said processor means further functions to determine if the number of parity errors in a block equals the number of errors in the associated block error byte and if that number is greater than one, and if so, then inserting indicators in each byte shown to have a parity error, said indicators being inserted at bit locations shown to have errors based on the contents of said block error byte.

16. A terminal as recited in claim 15 wherein the indicators are inserted by the processor means by or-ing the block error byte with each byte in the block with a parity error.

17. A terminal as recited in claim 14 wherein said processor means further functions to determine if the number of parity errors in a block is greater than the number of errors indicated by the associated block error byte, and if so, then inserting indicators into all of the bits of any bytes that has a parity error.

18. A terminal as recited in claim 14 wherein said processor means further functions to determine if the number of parity errors in a block is less than the number of errors indicated by the associated block error byte, an if so, then inserting indicators in all of the bytes in the block at the bit locations shown to have errors based on the contents of the block error byte.

19. A terminal as recited in claim 18 wherein the indicators are inserted by the processor means by or-ing the block error byte with all of the bytes in the block.

20. A transaction terminal for facilitating the off-line approval of transactions based upon the use of transaction cards each having an account number, comprising:

storage means for holding a transmitted data file containing information about a list of transaction cards in the form of a master table, wherein said master table is defined by a plurality of bit maps and wherein each listed card is represented by one indicator in each bit map; and

processor means, said processor means for detecting transmission errors, said processor means also for compensating for any ambiguous errors by placing an indicator in the table in each of the locations where a transmission error may have occurred so that information about listed cards will not be lost.

21. In a transaction network including a central processor, a plurality of remote transaction terminals and a plurality of transaction cards, each card having an account number associated therewith, said system for facilitating off-line approval of transactions comprising:

means at said central processor for creating a master table containing data derived from a list of transaction cards, said data being less than the entire account number of each card and wherein each listed card is represented by at least one indicator;

means for distributing the master table in a manner to be locally accessed by the remote transaction terminals;

means at each terminal for receiving data representative of the account number of a transaction card presented for a transaction; and

processor means operatively associated with the remote terminals for detecting transmission errors and placing an indicator in locations in the master table which are possibly in error, said processor means also for comparing the account number of a transaction card being presented for a pending transaction with the data in the master table and generating an output signal based on the outcome of that comparison.

22. In a transaction network including a central processor, a plurality of remote transaction terminals and a plurality of transaction cards, each card having an account number associated therewith, said system for facilitating off-line approval of transactions comprising:

means at said central processor for creating a master table containing data derived from a list of transaction cards, said master table being defined by a plurality of bit maps and wherein each listed card is represented by one indicator in each bit map;

means for distributing the master table in a manner to be locally accessed by the remote transaction terminals;

means at each terminal for receiving data representative of the account number of a transaction card presented for a transaction; and

processor means operatively associated with the remote terminals for detecting transmission errors and placing an indicator in locations in the master table which are possibly in error, said processor means also for comparing the account number of a transaction card being presented for a pending transaction with the data in the master table and generating an output signal based on the outcome of that comparison.