Patent GB-685441-A (GB)
Title: Improvements in or relating to calculating machines
IPC: G06F7/42
Filed: 1947-03-31
Abstract: 685,441. Digital electric calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd., (Valtat, R. L. A.). March 25, 1948 [March 31, 1947; March 31, 1947], Nos. 8642/47 and 8643/47. Class 106 (i). Calculating-apparatus for summing positive and /or negative numbers expressed in either pure or a mixed binary notation comprises switches for setting contacts to represent the numbers to be summed and chain circuits in which these contacts are connected in groups, each group representing a binary denomination, the entrypoint into each group except the first, in a chain circuit being connected only to exit points from groups in that chain circuit representing denominations lower than that of said group and the number and arrangement of such connections being determined by the significance in the notation concerned of the transfers between the successive binary denominations, so that the appropriate entry point into each group of a chain is energized via contacts in all the groups of that chain circuit representing denominations lower than that of said group whereby setting of the switches to represent the numbers to be summed sets up fully the necessary summing circuits so that no separate carry time is required. As shown in Fig. 5, the apparatus for translating a decimal number into the corresponding binary number comprises "units," "tens" and " hundreds " contacts 31 which are connected to relays 32 corresponding to powers of " 2." If, therefore, a decimal number is entered by closure of the appropriate contacts 31 the corresponding relays 32 are energized. The relays 32, Fig. 7, are arranged in groups corresponding to binary denominations and control contact arms 15 movable between two positions and forming links in a chain circuit. The number of contact arms 15 in. each link corresponds to the number of relays 32 in the corresponding binary denomination. A path through the chain is therefore set up in accordance with the energization or non-energization of the relays 32À Energization or non-energization of the relays 18 which are at the end of each link serve to indicate whether there is a " 1 " or a " 0 " in the corresponding binary denomination. Transfer from one denomination to another is automatically taken into account by arranging that each link of the chain, except the first, has as many starting-points as there are carries possible from the preceding denomination, the starting-point being determined by the path taken through the preceding link. It can be seen, therefore, that for every possible binary number within the range of the apparatus (in this case 2‹+2<SP>1</SP>+ ... 2<SP>9</SP>) there is a definite path through the chain and in the denominations in which a " 1 " occurs the corresponding relays 18 are energized. If desired the chain could be split into two parallel chains, one for determining and indicating, again by the energization of non-energization of relays, the number in the denomination, viz. " 1 " or " 0 " and the other for determining the " carry " to each denomination. In this case each link of the indicating chain is connected in parallel with the corresponding link of the carry chain. A similar arrangement of contacts, relays and contact arms, Figs. 6 and 8 (not shown), may be used to translate from the sterling notation into the binary notation. Fig. 3 shows the application of the invention to apparatus for adding or subtracting two binary numbers a and b, a being greater than b. A relay bx controls a contact arm to determine whether the subtract or add chain is required. As before, each link of the chain has contact arms controlled by associated relays a0 ... a9 and b0 . . . b9 which are energized when a " 1 " is present in the corresponding binary denomination of the binary numbers a and b, the said numbers being sensed from a punched card in known manner. The paths through the chains [a-6] and [a+b] therefore corresponds to the difference or sum of the binary numbers a and b and the result is indicated by the energization or non-energization of the relays +L0 ... +L5 to register a " 1 " or a " 0 " in each binary denomination. Transfer is again automatically taken into account by having as many entry points to each link as there are possible carries from the preceding link. Each chain is divided into two between the fifth and sixth binary denomination. Similar circuits, Figs. 9, 10 and 11 (not shown), are employed in accordance with the invention for the addition of numbers represented in a coded decimal notation. According to the first Provisional Specification a trigger pair of valves may replace the contact arms and there may be a mechanical form of the chain in which pins replace the contact arms and the rods in which the pins are carried replace the relays.