GB686986A - Improvements in or relating to electronic switching circuits - Google Patents

Abstract

686,986. Digital electric calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd. July 8, 1949 [July 9, 1948], No. 18103/49. Class 106 (i). [Also in Group XL(c)] An electronic commutator (i.e. a series of chain-connected circuits, each having two conditions of stability, so arranged that applied pulses cause each circuit in turn to assume a chosen stable condition) comprises two-valve trigger circuits connected by grid-controlled coupling valves to which pulses are applied simultaneously, and means for placing one trigger in a chosen stable condition to render the commutator responsive to the pulses. The commutator may be used to control the selective generation of pulse wave-forms in the calculating apparatus of Specification 673,759. As shown, four trigger circuits A, B, C, D are coupled by circuits H, I, J, K to form a ring- type commutator to which positive pulses are applied from a terminal 76 through a shaping circuit S. Each pulse is applied to the grid of amplifier 26, and a resultant negative pulse at the anode is passed through a differentiating circuit 33, 35 to the control grid of valve 27. The valve current is thus reduced and a positive pulse is sent via lead 74 and capacitors 75 to the grid circuits of coupling valves 37, 45, 52, 59. At the start of operations switch CBS is opened to cancel the bias on the grids of trigger valves A1, B2, C2, D2, which are thus rendered conductive (as shown by dots). The fact that A2 is not conducting, due to connection 38, will cause the grid of valve 37 to be initially at a higher potential than the grids of the other coupling valves. Thus the first pulse received renders only valve 37 conductive so that a negative pulse is sent over lead 44 to switch over trigger B. Valve B1 then conducts and a negative pulse is sent from its anode circuit through lead 66 and capacitor 67 to the grid of valve A1 to switch over trigger A. A capacitative connection 66a is provided also from supply line 13 to the grid of valve A2 so that any disturbance on the line is sent equally to both valves of the trigger. When B1 conducts the higher potential is applied to coupling valve 45 so that the next received pulse simi. larly switches over trigger C and returns trigger B to the condition shown. The next pulse switches over trigger D and returns trigger C, trigger A following trigger D, and so on indefinitely. In a modification, a negative pulse must be applied to trigger A before the commutator is responsive to pulses from the shaping circuit, the commutator then passing through a single cycle of operations only, and the commutator is reset, automatically by a switching circuit associated with the last trigger, or by connecting this trigger to an external pulse source.