Patent GB-687366-A (GB)
Title: Improvements in or relating to electronic adding devices
IPC: G06F7/50
Filed: 1950-06-09
Abstract: 687,366. Digital electric calculating-apparatus; statistical machines. BRITISH TABULATING MACHINE CO., Ltd., and BOWYER, A. W. Aug. 13, 1951 [June 9, 1950], No. 14458/51. Class 106 (i). An electronic apparatus for addition and subtraction particularly for use in conjunction with punched record cards comprises, a cyclically operable electronic device for algebraically' adding two or more numbers concurrently, each digital value being represented by an impulse timed in relation to the cycle. The apparatuscomprises electronic control means having two stable states, switchable from either state to the other by a value representing impulse and gating means controlled by said control means for each value to be added, means for applying to each gating means a train of pulses so timed that no two pulses of different trains overlap, at least one pulse of each train occurring in the interval between value representing impulses relating to adjacent digital values and electronic counting means operable to count individually the pulses produced by all said gating means, each of said gating means being operative to produce pulses corresponding to said input pulses when the related control means is in one state, and inoperative to produce such pulses when the related control means is in the other state. The apparatus shown in the Figure comprises three sets of trigger valves and associated gate valves, each set comprising a trigger and gate valve for each of four denominations. Thus, T4A represents the trigger stage for the thousands and G4A the associated gate valve, T3A the trigger valve for the hundreds and so on, the pattern being repeated for the set T4B &c. and T4C &c. Each set is similar in operation, a pulse train being connected to the trigger valve via a socket connection 11. Arrival of a pulse train causes the trigger valve to conduct and condition the associated gate valve so that when a positive pulse is applied to the line 2, all the conditional gate valves become conducting and the resultant negative voltage pulse produced is applied to a coded decimal counter 1 via the connections 9, 8, 7, 6, shown in the Figure. Operation.-The interval between sensing successive index points on a record card is divided into ten intervals or sub-digital cycles of pulses, these are further classified as A, B, C, &c. according to their position in time after sensing of an index point, for example, sensing of the " 9 " index point is followed by pulse 9A, pulse 9B, pulse 9C and so on. If the number of pulses of each sub-cycle fed to the counter is controlled by a digit of a number recorded on the card, then by utilizing, say, five sub-cycles and five groups of pulses, each group representing a digit, may be fed to the counter in one main digital cycle. Thus at the end of the digital cycle the sum of the five digits will be registered on the counter. All the trigger circuits are set in the " off " state before adding at " X " time by means of cam-controlled contacts. Nine pulses comprising the " A " subcycle are applied on line 2, nine " B sub-cycle pulses are applied on line 3 and nine " C " subcycle pulses are applied on line 4 during each main digital cycle. No sub-cycle impulses are produced corresponding to " 0 " time, since a pulse is not required for a counter registration of zero. For subtraction, the negative sign is conveniently indicated by an " X " perforation in a particular column, the sign detection being carried out during a pre-sensing cycle at a presensing station before the card is read. With negative numbers, the related entry trigger circuits are arranged to be " on " at the beginning of a digital cycle and accordingly the corresponding gate valves will pass pulses to the counter until the trigger circuits are switched " off," by the impulse resulting from sensing a perforation. In this manner the complement to nine of the number will be read into the counter. Specifications 315,881, [Class 106 (i)], 609,502, 673,759 and 674,952 are referred to.