Patent GB-688049-A (GB)
Title: Improvements in or relating to electric data-comparing circuits
IPC: G06F7/02
Filed: 1950-05-17
Abstract: 688,049. Digital electric calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd., and CARTWRIGHT, J. R. May 17, 1950, No. 12312/50. Class 106 (i). [Also in Group XL (c)] A data-comparing circuit comprises two devices for registering two sets of data which have two possible comparison relations, an input circuit and an output circuit connected to a low impedance path including a (germanium or thermionic) diode which is rendered conducting or non-conducting according to the existing comparison relation, a pulse applied to the input circuit being transmitted substantially unattenuated to the output circuit only when the diode is not conducting. As shown in Fig. 1, comparing circuits are used for controlling the transmission of a value from a binary counter comprising serially connected trigger pairs of triodes V1-V4 to a similar counter in which the trigger pairs V5-V8 are separated by pentodes V9-V11. Corresponding trigger pairs such as VI, V5, have their anodes connected through resistances R7-R10 to the anodes of diodes V12, V13, as shown. The diode cathodes are normally held at a fixed potential applied to line 8 such that a diode can conduct only if both the triodes connected to its anode are non- conducting. Thus, when a negative operating pulse is applied via line 7 to all the comparison circuits, if the corresponding trigger pairs are in the same condition the pulse will be shunted through a conducting diode, but if the triggers are in the opposite condition neither diode will be conducting initially and an effective negative pulse will be applied through a condenser such as C20 to the trigger V5, V6, V7 or V8. The triggers V6-V8 will then register the value on triggers V1-V4. Before the operating pulse is applied the triggers V5-V8 are isolated by closing switch 17 which applies a negative cutoff potential to the suppressor grids of valves V9-V11. The binary counters may be converted to decimal by using a locking valve as described in Specification 609,502. In a modification, Fig. 2 (not shown), the diode comparing units are serially connected for comparing the magnitudes of values registered on two counters. The comparing units may also be used for column-shifting upwards or downwards, e.g for multiplication or division, in a multidenominational decimal counter or accumulator, e.g. of the kind described in Specification 609,502, but with isolating pentodes between the trigger pairs. Fig. 5 indicates an arrangement for " column shifting " downwards a value in a non-uniform notation. For shifting, e.g., from units to tenths of minutes, corresponding trigger pairs 50 are connected to diode comparing units 51 which control the transmission of values to the next lower denominations in the manner described in connection with Fig. 1. For shifting down from units of hours, however, connections are made as shown to comparing units 52 to control the entries into the tens of minutes denomination and the value " 8 " trigger pair of the units of minutes. In addition, comparing units 53, 54, 55 are used to set auxiliary trigger units 56, 57, 58, 59 in accordance with the " 1," " 2 " and " 4 " value unit-of-hours trigger pairs. Pulses are subsequently applied successively to lines 60, 61, 62, 63 to reset the auxiliary triggers and transmit pulses over lines 64, 65 to the units of minutes denomination. Thus, e.g., if " 1 " is registered in the units of hours, triggers 58, 59 (representing " 4 " and " 2 " respectively) will be switched over under control of comparing unit 53 and, when subsequently reset by pulses on lines 62 and 63, will transmit pulses to the " 4 " and " 2 " value trigger pairs 50 of the units of minutes denomination, thereby adding " 6 " therein. The comparing circuits may be used with counters registering in other non-uniform notations, e.g. Indian currency, and counters comprising gas - filled valves. Specification 673,759 also is referred to.