Patent GB-698466-A (GB)
Title: Improved device for facilitating the detection of errors in symbol groups
IPC: G06Q20/00
Filed: 1951-05-29
Abstract: 698,466. Digital electric calculating-apparatus. REUMERMAN, T., and HELMIG, W. H. T. May 29, 1951, No. 12591/51. Class 106 (i). A device for determining for a symbol group composed from a given series of n symbols numbered in a predetermined order, a corresponding check symbol which indicates the remainder RN(G) obtained by dividing by a given number N a number G =#ai.ki as defined in Specification 693,250, comprises at least one electrical switching unit having N input and N output terminal and adapted to be actuated by associated symbol-inserting means in such a manner that upon insertion of a symbol having the number ai in position i of the symbol group, any input terminal Ap of the actuated switching unit is connected with an output terminal Dq such that q=RN[(ki+1p+bN)/ki+ai], where b is an integer, a voltage on an output terminal Dq corresponding to the insertion of a symbol being transferred to a corresponding input terminal Aq of the same or another switching unit, for insertion of the next symbol and so on, so that finally an indicator-actuating voltage appears on an output terminal Dr (or at corresponding input terminal Ar) where r=RN [(G+bN)/k 1 ]. In the devices described, the series of symbols are the digits 0-9 numbered accordingly, N=13, and ki=RN (10<SP>ii-1</SP>) so that K 1 =1, K 2 =10 and so on (six distinct values). Thus (Ki+1+bN)/Ki=10 whatever i may be, and q = RN (10p+ai) which means that identical switching units may be used for all digit position (Figs. 1, 2 and 4) or the same switching unit U (Fig. 7). Figs. 1 and 2 show opposite sides of a switching unit having input terminals A0-A12 connected to output terminals DO-D12 normally through zero-representing contact bridges P0-P12. If, however, one of the keys T1-T9 is depressed, these connections are interrupted by the displacement of a locking strip LS, and different connections are made through contact bridges embedded in the insulating key material and comprising contacts C1, C2 which connect input and output stripes IS, OS. The complete device shown in Fig. 4 comprises t-1 such units U1 - Ut-1 connected in series, and a simplified first switching unit having a normally closed zero contact C7 and single-contact-operating keys T1<SP>1</SP> - T91 which connect a positive voltage terminal to terminals A0 - A9 respectively of unit U1. The terminals DO - D12 of the last unit Ut-1 are connected to corresponding indicating lamps LO - L12. In the arrangement of Fig. 7, a single-bank keyboard is used and the unit U, while generally similar to that of Figs. 1 and 2, includes a zero key (TO) and an additional input terminal E, to which a positive voltage is supplied, which is connected to output terminal G or F according to whether a key is depressed or not. The output terminals DO - D12 are connected through decoupling resistors R with different ones or combinations of output relays RA-RD, so that when a key is depressed the relays corresponding to that terminal on which an operative voltage appears are energized, and held through terminals E, G and contacts ra1-rd1. When the key is released, corresponding input relays RP-RV are energized through terminals E, F and contacts ra2-rd2 and close contacts rp-rv to connect the positive voltage terminal to one of the input terminals A0-A12. All the relays are quick to energize and slow to de-energize. In operation, assuming a switch SW has been closed to energize relays RP, RQ and supply the voltage initially to terminal A0, the digits are set up from left to right, and the finally selected input line as determined by the relays RP-RV, which are held until the next key is depressed through contacts rp1-rv1, supplies an operative voltage also to the lamp LO-L12 indicating the correct check symbol. Additional keys may be provided for adding two or three noughts (Figs. 7A and 7B, not shown). In a modification, the output strips OS of a switching unit are straight, instead of as shown in Fig. 2, and special connections are embedded in the keys so that contacts C1 are connected to different-level contacts C2. A device of the invention may be incorporated in a mechanical calculating machine and may use the normal keyboard or have its keys actuated by electromagnets controlled by the machine keys. The indicated check symbol may be printed.