Patent GB-770182-A (GB)
Title: Improvements in or relating to gas-discharge tube counting circuits
Inventor: THREADGOLD RONALD
IPC: H03K23/82
Filed: 1955-02-02
Abstract: 770,182. Electronic counting apparatus. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Feb. 2, 1955 [March 11, 1954], No. 7063/54. Class 106 (1). A counting chain of discharge tubes fires successively in response to applied pulses the firing of one tube extinguishing all the others and the pulses are applied in parallel to gating circuits, one being positioned between each tube of the chain so that only that gate passes a pulse to the next tube if the preceding tube in the chain is conducting. Fig. 1 shows a counting chain comprising gas-discharge tubes VK2, VK4, &c. and intermediate gating tubes VK1, VK3, VK5, &c. The counting tubes VK2, VK4, &c. are primed by +50 volts applied to their trigger electrode. Input negative going pulses to be counted are applied at lead 11 and thus in parallel to the cathode of the tubes VK1, VK3, VK5. When a given counting tube, for example VK2, is conducting the rise in voltage across its cathode resistor R4 primes the associated gate tube VK3 so that when a negative pulse is applied to lead 11 VK3 fires and primes and thus fires the next tube VK4 in the counting chain. The flow of current through VK4 and the common anode resistor R3 extinguishes tube VK2, thus the count pro. ceeds along the chain. When the input pulse ceases the gating tube VK3 is extinguished and the next pulse fires gating tube VK5 which has been primed by the current flow in the cathode resistor R5. It will be noted that the input impedance of the pulse input circuit at lead 11 is not increased by increase of the number of stages in the counting chain. In a modification shown in Fig. 2, positive input pulses to be counted are applied via the phase reversing stage VT1 in parallel to the cathodes of the intermediate gating tubes and the counting stages are comprised by diode gas tubes VN1, VN2. In a modification, Fig. 5 (not shown), the gating tubes are replaced by biased diodes which are primed when the associated counting tube is conducting but which conduct only when an input pulse is applied. In a further modification, Fig. 6 (not shown), each counting tube has two resistors in series in the cathode and the gating circuit is applied to their junction, thus giving a low input impedance to the signal from the gating tube. In a modification shown in Fig. 4, comprising counting tubes VK6, VK7, &c. and intermediate gating tubes VK8, VK10, &c. auxiliary gating tubes VK9, VK11 are used; these are controlled from other than the input pulses applied from input 34 to the common cathode line of the gating tubes 35 so that by application of suitable control pulses the count may " skip " certain tubes of the chain or alternatively the count having g reached a given stage may then be caused to revert to an earlier stage without passing completely round the chain. Thus, if for example, the counter has reached the second stage with tube VK7 fired and it was required to revert to the first stage instead of proceeding the normal way to the third stage, no pulse would be applied to lead 36 but a positive priming impulse would be applied to lead 38 and a negative pulse to lead 39, thus gating tube VK9 would fire and this in turn would fire counter tube VK6 and extinguish tube VK7, the counter then functioning in the normal way. Fig. 3 shows a co-ordinate scanning field which is controlled by two counter circuits of the type previously described, the intersections of the field are marked by tubes VK1a, VK2a, VK1b, VK2b, &c. The tubes of the field are arranged to be scanned sequentially column by column. Thus, if it is assumed that the tubes in the first column are about to be scanned, tube VK1y will have been fired by a negative pulse over lead 16 from its appropriate pulse gate circuit and a bias applied over lead 17 to the triggers of all the tubes in the first column to prime them, the other counter circuit receives a negative pulse from lead 18 this is applied via lead. 19 to the cathodes of all the gates VK1x, VK2x and so on of the x counter. It is assumed that the tube VK1x is primed over lead 20 from the last counter and it fires therefore when the first pulse is received from the lead 18. When VK1x fires a negative pulse is applied over lead 21 to the corresponding counter tube and the latter fires and primes tube VK2x the pulse is also delivered to the common cathode lead 23 of all the tubes in the first row VK1a, VK2a, &c. since only VK1 a is primed this tube fires, the gate VKlx extinguishes and tube VK1a which is connected as a gate also extinguishes after passing the pulse to lead 24. The next pulse at lead 18 fires tube VK2x and this tube causes its corresponding counter to fire, thus the x counter will continue to be stepped by successive pulses in this way and tubes in the first column will fire in turn until the last tube in the column is reached, the last tube on firing applies a pulse to the pulse input of the y counter this fires the gate which was primed over lead 28 when counter tube VKly fired and this gate in turn applies a pulse to tube VK2y and the latter fires. When VK2y fires, VKly extinguishes and a priming bias is applied from the tube VK2y to the next tube of the y counter. The rows of the tubes are scanned again in turn, but this time tubes VK2a, VK2b will fire since this column of tubes is the only one in which the tubes are primed, the scan continues in this way with the y counter taking a step each time the x counter reaches its end position, thus all the columns are scanned in turn.