Patent GB-738294-A (GB)
Title: Improvements in or relating to data comparing devices
Inventor: TOWNSEND RALPH
IPC: G06F7/02
Filed: 1952-10-20
Abstract: 738,294. Digital electric calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd. Aug. 6, 1953 [Oct. 20, 1952], No. 26252/52. Class 106 (1). In apparatus for comparing two serial binary pulse trains having a two - state electronic storage device 6, Fig. 1, this device is set in a starting condition and its setting is compared by electronic means sequentially with the pulse positions of one pulse train, commencing with the least significant position, the comparing means and other pulse train controlling the setting of the device whereby its final setting indicates whether the number represented by one pulse train is greater or less than that represented by the other. In a modification, two two-state storage devices 16, 17, Fig. 2, indicate by their final settings whether one number is greater than, equal to, or less than the other. As shown in Fig. 1, two 32-digit binary numbers to be compared are stored in shifting registers 1, 2 comprising trigger stages A1-32, B1-32 and recirculation lines 4, 5. The storage device 6 also comprises a trigger stage whose two states, " 1 " and " 0," are used to indicate that the number (B) in 2 is less than or equal to, and is greater than, respectively, the number (A) in 1, the trigger being initially set to the " 1 " (equality) state by a pulse on line 11, e.g. from an associated computer. In operation, the two binary numbers are stepped along simultaneously by shift pulses on line 3, and whenever coincidence is detected between the states of triggers 6 and B32 a circuit 7 opens a gate 9 to allow clock pulses on line 10 (interspersed with the shift pulses) to pass to shift circuit 8, each clock pulse setting the trigger 6 to the same state as A32. Various modifications are described, e.g. the numbers may be in binary-coded decimal form, as described in Specification 678,427, the numbers may be stored on a magnetic drum instead of in shifting registers, and the coincidence circuit 7 may be replaced by an anti-coincidence circuit. In the modification shown in Fig. 2, the two trigger stages 16, 17 are initially set to " 0 " and " 1 " respectively by a pulse on line 18, and are controlled by circuits 12, 14, 15 and 13, 14, 15 corresponding respectively to 7, 9, 8, Fig. 1, so that the final settings are:- The outputs of triggers 16 and 17 are connected to the grids of triodes 19, 21 and a pentode 20 in such a manner that only one of the valves 21, 20, 19 conducts to produce a low output potential on the corresponding line 24, 23, 22, these lines corresponding respectively to comparison conditions (1), (2) and (3) above. Circuit details. The coincidence circuit 7, Fig. 1, comprises a double triode V1, Fig. 3, having each grid connected to two equal resistors the other ends of which are connected by lines 29, 31 and 30, 32 to the anodes of triggers 6 and B32. If the triggers are in like states the lines of one pair will both be at a high potential, thus producing a high potential on the corresponding grid and on the cathode output line 33 which is connected to the grid of the normally non-conducting right-hand side of a double triode V2, Fig. 4, forming the gate 9, Fig. 1. When a negative pulse on line 10 is applied to the other left-hand grid of V2, the high potential on line 33, if present, will cause conduction in the right-hand side, and the resultant negative anode pulse is applied to the cathodes of double diode V4 (circuit 8, Fig. 1). The diode V4 is so connected between the anodes of double triode trigger circuit V3 (A 32, Fig. 1) and the grids of similar trigger circuit V5 (6, Fig. 1) that if these triggers are in unlike states the negative shift pulse from V2 will be gated through one half of V4 so as to switch over V5 to the state of V3. Similar shifting circuits are provided between the stages of registers 1 and 2. Specification 738,269 also is referred to.