GB1125293A - Improvements in or relating to calculating devices - Google Patents

Abstract

1,125,293. Calculating apparatus. A. H. F. RICHARDSON. 2 Sept., 1966 [20 Oct., 1965], No. 44512/65. Heading G4B. A device for calculating the check digit associated with an account number comprises a sheet having thereon a circular spaced sequence of numerical markings divided into a plurality of segments, an arcuate slot in each segment with the markings therealong, a second sheet rotatable about the centre of markings and having a plurality of spaced holes or indentations arranged to show in the slots and having marked thereon a succession of sequences of check numerals, one of which numerals at a time shows in an aperture or recess in the first sheet. As illustrated, the second sheet is a disc 2 having 99 apertures 2a and the sheet is a plastics member 1, having nine segments, each including an arcuate slot 1b and having an aperture 1a through which repeated symbols 0-9 and A (A = 10) can be viewed. The check digit is calculated by multiplying the digit in each denominational order of an account number by a different constant, adding the results together, dividing by a modulus and taking the difference between the remainder and the modulus. In the illustrated embodiment the constant for the first denominational order is 3, the modulus 11 and the symbols 0-9 are positioned according to the following:- position = 1- remainder of 3n/11 where n = 0, 1,...9; e.g. for digit 6 (i.e. n = 6), position = 11-7 = 4. The positions for the digits in the other denominational orders are calculated similarly. Thus to calculate a check digit it is sufficient to locate 0 in aperture 1a and to dial the digit of each denomination in the corresponding slot and thus to move the disc clockwise. Alternatively the calculation may commence with a specified number positioned in aperture 1a.