Patent GB-779526-A (GB)
Title: Improvements in or relating to cold cathode glow discharge counting and scaling tubes and circuit arrangements therefor
Inventor: TOSSWILL CHRISTOPHER HALY
IPC: H01J17/48
Filed: 1954-04-06
Abstract: 779,526. Electronic counting apparatus. MULLARD RADIO VALVE CO., Ltd. March 7, 1955 [April 6, 1954], No. 10054/54. Class 106 (1). [Also in Group XL (a)] A cold cathode scaling tube comprises an anode and a plurality of cathode electrodes adapted to provide, when in operation, a plurality of rest positions for the glow discharge, the arrangement being such that the energy of an output pulse obtainable from one of the cathode electrodes is greater than that of an input pulse required to cause the glow discharge to move from one rest position to the next. This enables one tube to be connected to a next one in cascade without the necessity of an intermediate amplifier. A binary counting tube comprises an insulating disc 1, Fig. 1, supporting ten electrodes, five of which are associated with each rest position. Each set of five electrodes is divided into a rest group and a transfer group. Thus one set comprises a rest group formed by a main cathode 5 and an auxiliary cathode 6 and a transfer group formed by an input electrode 7, an extinguishing electrode 8 and a final transfer electrode 9. The other set comprises a rest group formed by a main cathode 10 and an auxiliary cathode 11 and a transfer group formed by an input electrode 12, an extinguishing electrode 13 and a final transfer electrode 15. The electrodes, with the exception of the main cathodes 5 and 10 are each provided with a cranked or L-shaped end. A disc anode 2 is supported by a stiff wire 3. The input electrodes 7 and 12 are connected together, the extinguishing electrodes 8 and 13 are connected together, and the auxiliary cathodes 6 and 11 and the final transfer electrodes 9 and 15 are all connected together. These connections may be effected internally or externally of the tube. In the first rest position the glow discharge envelops cathodes 5 and 6 so that they are at the same potential as are also electrodes 9, 11 and 15 by virtue of the interconnection with auxiliary cathode 6. On the receipt of a negative input pulse on the input electrodes 7 and 12 which are held at the voltage of the auxiliary electrodes 6 and 11 and due to ionization in the proximity of the main discharge, a small discharge occurs between anode 2 and the input electrode 7 serving to extinguish electrodes 5 and 6 and to trigger extinguishing electrode 8, which is normally maintained at a potential lower than the input electrodes. The current through extinguishing electrode 8 prevents the anode voltage rising sufficiently to restrike the discharge to cathodes 5 and 6. The voltage of the auxiliary cathode 6 and all electrodes connected to it falls as that of the extinguishing electrode 8 rises, whereupon the discharge spreads over the final transfer electrode 9, which causes this electrode to rise in voltage. When the voltage reaches a certain value the discharge transfers to main cathode 10 which is considerably negative with respect to final transfer electrode 9. Main cathode 10 rises in voltage and the glow then envelops main cathode 10 and auxiliary cathode 11. The discharge remains at this rest group until the next input pulse is applied to the input electrode 12. The number of rest positions may be increased to ten to provide a decade counter tube. Fig. 5 shows two such tubes connected in cascade. Parts of the circuit have been omitted in the interests of clarity. In each tube the oddnumbered main cathodes 1-7 are inter-connected and the even-numbered main cathodes 2-8 are interconnected, while the output cathode 9 and the zero cathode 0 have individual output leads. Similarly, the input electrodes I, the extinguishing electrodes E, and the final transfer electrodes F and auxiliary cathodes G are interconnected, while the anode A has an individual output lead. The output cathode 9 of the first tube is connected to earth through a capacitor C5 and to - 50 volts through a resistor R5. The input electrodes I of the second tube are connected to the output cathode 9 through a capacitor C11. Both capacitors C5 and C11 charge up when the discharge arrives at cathode 9 and discharge through the resistor R5 when the discharge leaves cathode 9, the drop in voltage firing the second tube. In order that the second tube shall be certain of firing, the input electrode I is arranged to strike before C5 and C11 have completely discharged. During the brief period that current is passing to the input electrode I, capacitors C5 and C11 charge up again and then discharge again after the current ceases. To prevent this second fall in voltage causing the second tube to step a second time, the extinguishing electrodes E of this tube are connected through a resistor R8 to the zero main cathode 0 of the first tube. The extinguishing electrodes E are also connected to earth through a capacitor C8 in parallel with a rectifier D4 which prevents the electrodes being driven negative with respect to earth. The time constant of R8, C8 is arranged to be about five times that of R5, C5, so when the discharge arrives at zero main cathode 0 the voltage on the second tube extinguishing electrodes E is raised and remains so for a while after the discharge has left the zero main cathode, but returns to normal by the time the next legitimate pulse arrives. The sensitivity of a tube to an input pulse may be increased, but with consequent reduction of speed of operation, by removing the diode connection to the input electrodes I and connecting these electrodes through a large resistance to a voltage such that a priming discharge of a few microamps. exists between the anode and the input electrode associated with the rest position containing the glow discharge.