Patent GB-698748-A (GB)
Title: Improvements in or relating to checking devices for calculating apparatus
IPC: G06Q40/00
Filed: 1951-02-28
Abstract: 698,748. Digital electric calculating-apparatus. REUMERMAN, T., and HELMIG, W. H. T. Feb. 28, 1951 [Feb. 28, 1950], No. 4821/51. Class 106 (i). Calculating-apparatus having a register comprising figure wheels is characterized in that the figure wheels are included in an electric computing device computing from the positions of the figure wheels a check symbol, i.e. the remainder obtained on division of the member displayed by a certain key number, and registering the check symbol. The totalizer wheels 14 of a calculating-machine, Fig. 1, each carry, on each side, radially and circumferentially spaced contact surfaces 64, Fig. 5, the surfaces on one side being electrically connected to respective surfaces on the other side. Between each pair of totalizer wheels, is a stationary disc 50, Fig. 4, having several contact brushes spaced on each side so as to engage the contact surfaces on the adjacent totalizer wheels, the brushes on the two sides being inter-connected. Adjacent the highest and lowest order wheels respectively are further stationary discs having contact brushes for engaging the contact surfaces on the adjacent totalizer wheels, one of the brushes on each disc being connected to a source of potential. The other brushes on one disc are connected to earth through lamps 20 and those on the other disc are similarly connected to earth through lamps 21. The arrangement is such that two circuits are always completed through the succession of discs and totalizer wheels, the circuits passing respectively through one of the lamps 20 and one of the lamps 21. The lamps represent checking numbers which are equal to the remainders obtained by dividing the number registered on the totalizer by nine and eleven respectively. These checking numbers have the property that the checking number for an amount corresponding with the result of a calculation is equal to the number obtained by performing the same calculation on the checking numbers for the original amounts. The " 9 " checking number is equal to the sum of the digits of the amount less the appropriate multiple of 9 which leaves a number less than 9. The " 11 " checking number is equal to the sum of the digits in the first, third and so on denominations less the sum of those in the second, fourth and so on denominations, increased or reduced by a multiple of 11 to produce a positive number less than 11. The electrical circuits described compute the checking numbers in this way. In the arrangement shown, the calculating machine has two extra columns of keys 18, 19 on which may be set the " 9 " and " 11 " checking numbers for an amount set on the main keyboard 15. Each column 18, 19 is associated with a number wheel 16, 17 so that when a calculating operation is performed, a similar operation is applied independently to the checking numbers. Thus, at the end of a calculation, the checking numbers for the result should equal the numbers displayed by the wheels 16, 17. These wheels also carry contact surfaces and are so arranged in the circuits of the lamps 20, 21 respectively that the number registered by each is subtracted from the corresponding checking number for the result, so that the lamps indicate the differences between these numbers which should, in the absence of errors, equal zero.