Patent GB-708119-A (GB)
Title: Improvements in or relating to a gaseous electric discharge tube
IPC: H01J17/48
Filed: 1951-03-22
Abstract: 708,119. Electronic counting apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. March 22, 1951 [March 31, 1950], No. 6982/51. Class 106 (1). [Also in Group XL(a)] A counting circuit comprises a multi-gap coldcathode tube 1 (see Group XL(a)), having a hollow cylindrical anode 2 and cathodes 4 to 13 each having a knee or root remote from the anode and a tip member nearer the anode and spaced equidistantly from the anode and the root of an adjacent cathode. Alternate cathodes are connected in common through individual load resistors 35 or 36 to bus-bars 59 and 60 to form two separate groups of cathodes. Input pulses applied at terminals 41 are passed via condensers 42 to the grids of the two triode sections 43 and 44 of a duo-triode flip-flop circuit. Triode sections 45 and 46 of a second duo-triode are connected as cathode followers to couple the flipflop circuit to the counting tube 1. When triode 43 is conducting, the voltage drop in the corresponding coupling resistor 50 causes the grid of triode 45 to become less positive. The resultant decrease of current through the cathode load resistor 52 of triode 45 causes a lowering of the potential of cathodes 4, 6, 8, 10 and 12, since bus-bar 60 is connected directly to the cathode of triode 45. At the same time, triode 44 is non-conducting so that a high positive potential is applied to the grid of triode 46, thus producing a large voltage drop in its cathode load resistor 52 and raising the potential of bus-bar 59 and cathodes 5, 7, 9, 11 and 13. Conversely, conduction in triode 44 will cause lowering of the potential of bus-bar 59 and elevating of the potential of bus-bar 60. The crystal or thermionic rectifying diodes 64 form parts of two auxiliary circuits designed to cause an overlap of the potential changes which take place between adjacent cathodes. The auxiliary circuits will oppose a sudden positive increase of the potential on the grid of either triode 45 or 46 since the diodes 64 conduct for this polarity of change, but for a sudden decrease of potential of either grid the corresponding diode will not conduct, thus allowing as rapid change in the negative direction as the remaining time constants of the system will permit. In some cases, the distributed capacitances of the electrodes together with the physics of the glow discharge growth and decay may introduce enough of this overlapping action to enable the auxiliary circuits to be omitted. To initiate a glow discharge on cathode 4, the normally closed switches 37, 38 and 39 are momentarily opened, causing triode 43 to conduct, thereby lowering the potential of cathode 4. On receipt of a negative input pulse at terminals 41, the conduction is reversed between triodes 43 and 44, but due to the effect of capacitance 62 in the auxiliary circuit, the potential on bus-bar 60 does not immediately rise so that both cathodes 4 and 5 are momentarily maintained at approximately equal potentials, and a double discharge occurs, one on the tip member of cathode 4 and the other on the root of cathode 5. When the delaying action of capacitance 62 ceases, the potential of bus-bar 60 and cathode 4 rises and the discharge on cathode 4 is extinguished due to the action of the common load resistor 48. The glow on the root of cathode 5 then moves along the cathode under the influence of the electrostatic gradient and comes to rest on the tip member of cathode 5. The discharge is thus stepped one cathode along the array for each input pulse. For cascade operation, the pulses appearing across the load resistor 36 of cathode 4 are available at the output terminals 40. A simplified arrangement (see Group XL(a)) comprises a tube having cathodes connected in common through individual resistance-capacity circuits to form a single group, to which negative extinguishing pulses are applied directly to step a discharge around the array. Specification 708,114 is referred to.