Patent GB-750116-A (GB)
Title: Electron tube counting circuits
IPC: H03K23/82
Filed: 1954-02-18
Abstract: 750,116. Multi - stable state circuits. NATIONAL CASH REGISTER CO. Feb. 18, 1954 [April 21, 1953 ; April 21, 1953], No. 4745/54. Class 40 (6). [Also in Group XIX] An electron discharge tube " ring " counting circuit consisting of two groups of gas-filled electron discharge tubes, the tubes being connected to enable the discharging tube of one group to prime a tube of the other group so that said primed tube may fire in response to an input pulse, is characterized in that each group has associated therewith a blow-out tube additional to the tubes of the group, the blow-out tube of each group being controlled by the operation of a tube of the other group to extinguish any discharging tube in its associated group. The " odd " and " even "-numbered counting tubes, Fig. 1, constituting the said two groups, and together forming one denominational bank of a scale of ten counter, have their anodes connected together and to an H.T. supply via resistors 36, 24, and to the anodes of their associated blow-out tubes 62, 55 respectively. The grids of the blow-out tubes 55, 62 are negatively biased and coupled via condensers 61, 40 to the connected cathodes of the " odd " and even " groups respectively, the counting tubes being constructed as described in Specification 717,952. When the counter is registering unity only tube " 1 " is discharging and the next higher tube, tube " 2 " is " primed " by virtue of a connection 41 between the grids of tubes " 0 " and " 1 ". In these circumstances, a negative input pulse applied at terminal 43 causes a negative pulse to pass through a double diode 46 to the cathodes of both groups, thus increasing the potential across each tube and causing tube " 2 " to fire, which raises the potential of the " even " cathodes and causes a positive pulse to be applied to the " odd " blow-out tube 62, which therefore fires, causing the " odd " anodes to decrease in potential, and thus extinguishes'tube "1." Tube 62 is then extinguished by the voltage dropped across its cathode load. Thus the result of an input pulse when tube " 1 " is conducting is to fire tube'" 2 " and to extinguish tube "1," tube 62 firing during the transition period. Further input pulses successively fire the remaining tubes and an output pulse appears across a condenser 79, connected to the cathode of a selfextinguishing tube 65, every time tube " 0 " fires, thus providing a tens transfer to the next higher denomination. In a second embodiment, Fig. 2 (not shown), the anodes of the blow-out tubes, which in this case are hard tubes, are connected to the two groups of counting anodes via isolating condensers, thus permitting the blow-out tubes to have an independent H.T. supply higher than that on the anodes of the counting tubes, causing them to produce stronger blow-out pulses. In a third embodiment, Fig. 3 (not shown), in which the blow-out tubes are normally conducting hard pentodes, instead of the anodes of one group of counting tubes being connected to the anode of the blow-out tube associated with the other group, as in Fig. 1, they are connected, via an isolating diode, to its control grid, the effect of the firing of a tube in the said one group being to pass a negative pulse to the blow-out tube associated with the said other group, causing a reduction in current through it which, in turn, causes it to send a positive blow-out pulse, via its anode and a blocking condenser, to the cathodes of its associated group, thus extinguishing any discharging tube in that group. Negative input pulses are applied direct to the cathodes of all the counting tubes via an R.C. filter. In a fourth embodiment, Fig. 4, the blow-out tubes are hard pentode control tubes 175, 176, which do not emit pulses like the blowout tubes but " see-saw " at the rate of the input pulses, one of them always conducting. Suppose tube " 1 " is discharging, then the raised potential of the " odd " cathodes is communicated to the control.grid of the " even " control tube 175 by a resistor 182 causing it to conduct, thus lowering the potential of the " even " anodes to a value sufficiently low to prevent any " even " tube firing. When a negative input pulse is applied at terminal 187 it is transmitted via a double diode 190, resistors 193, 177 and cuts off tube 175 thus allowing the potential of the " even" anodes to rise and causing tube " 2 to fire, which causes a positive pulse to be passed to the control grid of the " odd " control tube 176 which then conducts and lowers the potential of the " odd " anodes thus extinguishing tube "1" and preventing any other " odd " tube firing. Further pulses cause the continued sequential firing of the tubes, an output being delivered via a tube 201 which fires every time tube " 0 " fires.