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Error Correction and Substitution Detection

IP.com Disclosure Number: IPCOM000042491D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 18K

IBM

Related People

Barnes, WA: AUTHOR [+3]

Abstract

A multi-digit number is provided with an error correction digit and a substitution detection digit which enhance the ability of an automatic reading system to reliably read the number. The error correction digit permits computation of any single digit in the number which is found unreadable by the automatic reading system. The substitution test digit verifies that the digits read by the automatic reading system have been correctly identified. The error correction digit (ECD) is computed by a decimal addition of all digits, retaining only the units digit. Example: Record 004624397742148693701796 Result of decimal add = 109 ECD = 9 The substitution detection digit (STD) is computed by a decimal addition, with 1,2,1 weighting, retaining only the units digit.

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Error Correction and Substitution Detection

A multi-digit number is provided with an error correction digit and a substitution detection digit which enhance the ability of an automatic reading system to reliably read the number. The error correction digit permits computation of any single digit in the number which is found unreadable by the automatic reading system. The substitution test digit verifies that the digits read by the automatic reading system have been correctly identified. The error correction digit (ECD) is computed by a decimal addition of all digits, retaining only the units digit. Example: Record 004624397742148693701796 Result of decimal add = 109 ECD = 9 The substitution detection digit (STD) is computed by a decimal addition, with 1,2,1 weighting, retaining only the units digit. Example: Record 004624397742148693701796 11111 1 Weight 12121 etc. ----------2
Result of decimal add = 156 STD = 6 Example: Record as printed (with check digits)

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Error Correction During the read operation the digits of a record with a single reject are again added excluding the check digits and the rejected character (indicated by 'F'), to compute a test digit. The rejected character (repair digit) is computed by subtracting the test digit from ECD. Example: Record prior to correction 96462F397742148693701796 Rejected character Result of decimal add = 105 Test digit = 5 Result of ECD - TD 9-5=4 (repair digit) Repaired record 964624397742148693701796 Corr...