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# Check Digit Calculator

IP.com Disclosure Number: IPCOM000091255D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 35K

IBM

## Related People

Rossel, A: AUTHOR

## Abstract

Check digit calculator 10 is a manually operated device for computing check digits for self-checking numbers. Base member 12, drawing A, is provided with indicia arranged as shown. Stop 13 is fixed to base 12. Dial 14, drawing B, overlies base 12 and is rotatable relative to it. Hole 15 in dial 14 is a reference hole. Calculator 10 is reset by dialing hole 15 in one of the directions indicated against stop 13. The number of characters in the base number is odd or even. This determines the direction of dialing for resetting calculator 10.

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Check Digit Calculator

Check digit calculator 10 is a manually operated device for computing check digits for self-checking numbers. Base member 12, drawing A, is provided with indicia arranged as shown. Stop 13 is fixed to base 12. Dial 14, drawing B, overlies base 12 and is rotatable relative to it. Hole 15 in dial 14 is a reference hole. Calculator 10 is reset by dialing hole 15 in one of the directions indicated against stop 13. The number of characters in the base number is odd or even. This determines the direction of dialing for resetting calculator 10.

With calculator 10 reset, the characters of the base number are located in the dial holes and dialed in the directions indicated. The direction of dialing reverses on each successive operation. After all characters of the base number are dialed, the check digit appears in window 20.

Generation of a check digit, modulus-10, is accomplished by multiplying the units position and every alternate digit position of the base number by 2. The digits in the product and the digits of the base number not multiplied by 2 are crossfooted. The crossfooted total is then subtracted from the next higher number ending in zero. The difference is the check digit. By resetting the dial, the alternating sequence is taken into account. Base member 12, in addition to the circularly arranged check digits 17, contains two tables 18 also arranged circularly. One table represents digits to be added and the other represents digits to b...