Patent GB-677985-A (GB)
Title: Improvements in or relating to electric counting circuits
Inventor: REEVES ALEC HARLEY
IPC: H03K29/00
Filed: 1947-07-22
Abstract: 677,985. Discharge apparatus. STANDARD TELEPHONES & CABLES, Ltd. July 16, 1948 [July 22, 1947], No. 19616/47. Class 39 (i). [Also in Group XL (c)] In a pulse counting device, comprising a cold cathode gas-filled sequence electric discharge tube, which is a development of the arrangements described in Specifications 665,817, [Group XIX], and 665,818, to which reference is made, the maintaining battery is omitted so that there is no discharge in the gaps in the intervals between pulses. The tube 1 has a common strip or wire anode 2 and an indented cathode 5 having a shorter starting gap 4. Additional cathodes 7 and 8, the latter consisting of a small plate, are arranged at the same distance from the anode as the indentations of cathode 5 while the spacings between the last point on cathode 5, cathode 7, and the left-hand edge of cathode 8 are the same as the inter-point spacing on cathode 5. Negative input pulses to be counted are applied to terminal 19 and thence pass to cathode 5 via a delay network 22 and blocking condenser 21, to cathode 7 via delay network 22, blocking condenser 21 and resistance-capacity network 9-10, and to cathode 8 via blocking condenser 20, resistance-capacity network 11-13, and the primary winding of output transformer 12. The delay time of network 22, which may take any suitable form, is greater than the build-up time of the leading edge of the input pulses, but less than the pulse duration. The pulse amplitude is such that, in the absence of ionization, only the shorter gap 4 will fire, so a first pulse fires gap 4, the discharge ceasing as soon as the pulse ceases, as there is no maintaining battery. Due to ionization coupling, the next pulse fires the first two points on cathode 5, and so on until all the points on cathode 5 fire together on some later pulse. Battery 18 and rectifier 17 serve to limit the voltage across the tube to a value substantially constant and independent of the number of points on cathode 5 that are fired, the potential of the battery being such that the rectifier becomes non-conducting when all the points on cathode 5 are discharging. The next pulse will fire cathode 7 and all the points of cathode 5. The value of the resistancecapacity network 9-10 is such that the next few pulses are unable to re-fire cathode 7, so the next pulse fires cathode 8, but owing to the direct connection from terminal 19 to cathode 8 via condenser 20, the pulse reaches cathode 8 before it reaches cathodes 5 and 7 by a time equal to the delay of network 22. Cathode 8 has a relatively large surface and the current which flows between cathode 8 and anode 2 as the pulse voltage builds up, in passing through the anode load 3 limits the anode voltage to such a value that none of the points of cathode 5 can fire. The next pulse cannot re-fire cathode 8 owing to the charge on condenser 13 of the resistance-capacity circuit 11-13, and the only gap which can fire is the starting gap 4, so the sequence of events starts again. An output pulse is obtained from terminals 16 every time cathode 8 fires. Specification 639,827 also is referred to.