Patent GB-726526-A (GB)
Title: Improvements in or relating to electrical information storage circuits
IPC: H04L25/04
Filed: 1953-12-11
Abstract: 726,526. Pulse circuits. STANDARD TELEPHONES & CABLES, Ltd. Dec. 11, 1953 [Dec. 15, 1952], No. 34513/53. Class 40 (6). [Also in Group XL (b)] In an electrical circuit in which a coded combination of impulses is stored as a pattern of operated tubes on a chain of cold-cathode gaseous discharge tubes interconnected in sequential consecutive pairs so that a stepping pulse applied to all the tubes causes the pattern to progress as a whole one stage along the chain in response to each stepping pulse, as described in Specification 663,574, a first connection includes a resistor from the anode of each tube to a positive supply and a second connection includes a rectifier from the anode of each tube to a further supply whose voltage is less than that of the first supply and is compatible with reliable operation of said tube, the rectifiers being poled as to be in the direction of easy conductivity for current flowing away from the anodes of their associated tubes and the effect of said rectifier being to increase the maximum operating speed attainable with said circuit by reducing the risk of the tubes being fired incorrectly. As shown, the rectifier MR3 is connected between sources of 280 v. and 260 v. through a resistor R1, for example of 50K ohms, connected in the anode circuit of the tube T1. The step pulse which succeeds that which extinguished T1 and fired T2 could cause T2 to fire when not desired, i.e. when the tube preceding T1 was quiescent when the firstmentioned step pulse was applied, because the capacitor C1 retained enough charge to cause T2 to fire at the end of that step pulse, and the incorporation of the rectifier MR3 is effective to limit the actual value of the positive potential on the anode of the tube when it is quiescent. In the case in which a stepping pulse requires the firing of successive tubes, such as T1 and T2, the firing of the trigger-cathode gap of T2 causes a decrease in the anode potential of T1 while the firing of the main anode-cathode gap of T1 reduces the potential at the trigger electrode of T2, and whichever tube of T1 and T2 fired first could have a detrimental effect on the operation of the other tube. When a tube is extinguished, since a current of 0.4 mA. flows through R1 and MR3 in series, the anode of a tube is effectively decoupled from the trigger electrode of the next tube and vice versa until a current greater than 0.4 mA. is drawn either by the main anode-cathode gap of such tube or by the trigger-cathode gap of the next tube. The grid limiting resistors included in the circuit shown in Specification 663,574 have been omitted and this reduces the charge retained by C1 in its charging circuit comprising R1, C3, MR1, but not including any grid resistor. The circuit shown in Fig. 2 is arranged to produce very square pulses for the stepping pulses. When the pentode V1 is drawing current the cathodes of the register tubes are held at earth potential via metal rectifiers MR4 ... MR7. When V1 is cut off by a negative pulse, the anode voltage of VI, which is applied to the cathodes of the register tube, rises rapidly and to ensure that the time rise is independent of the number of tubes discharging, the positive-going impulse from the screen of V1 is applied to the grids of the double-triode V2 connected as a cathode-follower and the change in its cathode voltage sharpens the step pulse. When the input pulse to V1 ends, the valve again conducts, and as it can absorb a large peak overhead, the voltage applied to the cathodes of the tubes T1, T2 ... falls very sharply.