Patent GB-632212-A (GB)
Title: Improvements in or relating to thermionic valve commutators or the like
IPC: G06F9/32
Filed: 1947-02-28
Abstract: 632,212. Pulse counting circuits. BRITISH TABULATING MACHINE CO., Ltd. Feb. 28, 1947, No. 5895. Convention date, March 1, 1946. [Class 40 (vi)] A hard valve trigger circuit used in a reversible electronic commutator comprises a pair of valves having two electron paths, the first path in each being cross-coupled to the corresponding path in the other valve to form a trigger pair while the second path functions as a pulse gate under control of the trigger action. Each of the circuits C1, C2, C3 has two stable states and comprises a pair of pentode valves 95a, 95b, coupled by a common cathode resistance 96 and by cross-connection of the screens over a pair of potentiometers comprising resistances 60a, 61a, 62a and 60b, &c., and condensers 63a, 63b respectively. Only one valve is conductive in either stable state, and the application of a negative pulse to its grid via condenser 59a or 59b causes conduction to be transferred to the other valve of the pair, the circuit being reversed to the opposite state. Conduction normally occurs to the screens, the standing cathode bias preventing anode current flow when the lines 97, 56 and the suppressor grids are at the same potential; anode current flows, however, in all conductive valves if a positive pulse occurs on the line 97. In trigger pairs in on condition the valve 95b is conductive and a negative-going impulse is produced at the anode, whereas in off pairs 95a is conductive and responds instead. Reversible commutator. The trigger circuits are interconnected over inter-relating circuits which produce sequential reversal when impulses appear on the line 97, either in a forward sequence C3, C2, C1, being switched on in turn followed by switching off in the same order, or in the reverse order as determined by a sequence-controlling trigger circuit FR. Either cycle may be interrupted or resumed by means of a switch 103. Switching impulses are obtained by differentiation in the network 75, 76 of a square waveform generated by a multivibrator M, positive-going components being suppressed by a valve 86 with grid current bias while negative components are inverted and produce positive-going impulses on the line 97. Corresponding negative-going pulses appear at the anodes of all conductive trigger valves and are transferred to the associated inter-relating circuits, which comprise inverting triodes 3a and 3b and pentode pairs 3aF, 3aR and 3bF, 3bR. For forward commutation the pentodes 3a, 3bF are held conductive by raising the potential of the grid line FF, while for reverse operation the potential of RR is raised and the pentodes 3a, 3bR conduct. Conduction normally occurs to the screens, anode current only flowing in a conductive valve when the suppressor grid is positively pulsed by the associated triode. The negative impulse then produced at the pentode anode is transferred to the grid circuit of an element in the trigger chain C1, C2, C3, the interconnections being such as to result in. sequential commutation. Sequence-controlling trigger circuit. The circuit FR comprises a pair of triode valves with cathode coupling and with the anodes crosscoupled in a manner similar to the circuits C1 &c. described above. In forward status the valve 64b is non-conductive and holds the line FF at its maximum potential, while for reverse operation 64a is non-conductive and the potential of the line RR is held raised ; reversal is obtained by applying a positive pulse to the grid of the non-conductive valve via a condenser 59a or 59b. Specification 638,066 is referred to.