US3544837A - Electronic counting or timekeeping system using glow discharge tube - Google Patents

Description

Dec. 1, 1970 J. MANGALY 3,544,837

ELECTRONIC COUNTING OR TIMEKEEPING SYSTEM USING GLOW DISCHARGE TUBE /MAINTAINING VOLTAGE [1 .6.3

Filed Nov. 1. 1968 I I s I Q l G R I I I R, 2 I 510 L .l 5253 E4 5 E6 E8 59 It 51/ E12 20 PULSE FLOP D! A.(.SUPPL L 111 CI 2o 21 22 TRANSFER VOLTAGE 'b 111 g 0% Arrvs,

United States Patent 3,544,837 ELECTRONIC COUNTING OR TIMEKEEPING SYSTEM USING GLOW DISCHARGE TUBE Joseph Mangaly, Glasgow, Scotland, assignor to General Time Corporation, Stamford, Conn., a corporation of Delaware Filed Nov. 1, 1968, Ser. No. 772,649 Int. Cl. H01j 17/36; H03k 25/00 US. Cl. 31584.6 13 Claims ABSTRACT OF THE DISCLOSURE The present invention relates generally to electronic timekeeping and indicating systems and, more particularly, to an improved electronic timekeeping and indicating system having an improved counting system utilizing a glow discharge tube.

In copending applications Ser. No. 524,027, filed Feb. 1, 1966, by H. A. de Koster and entitled Electronic Clocks; Ser. No. 581,592, now Pat. No. 3,466,498, filed Sept. 23, 1966, by H. A. de Koster and entitled Electronic Counters; Ser. No. 581,591 now abandoned, filed Sept. 23, 1966, by H. A. de Koster and M. Ingenito and entitled Electronic Counters; and Ser. No. 705,793, filed Feb. 15, 1968, by H. A. de Koster and M. Ingenito and entitled Electronic Counting or Timekeeping System Using Glow Discharge Tube, all of which are owned by the assignee of the present invention, there are described several different electronic timekeeping and indicating systems having improved counting systems utilizing glow discharge tubes. The counting is achieved by stepping the glow discharge along successive cathods which are arranged to serve as time indicating elements as well as operative elements of the electronic counting system. As explained in detail in the copending applications, the glow discharge is formed and transferred by the application of controlled electrical potentials across the various gaps between the indicating cathodes and one or more anodes.

It is a primary object of the present invention to provide an improved glow discharge timekeeping and indicating system having an improved directional control system for controlling the direction of movement of the glow discharge as it is stepped along a series of electrodes in response to electrical input signals representing predetermined time intervals.

A more particular object of the invention is to provide such an improved directional control system which permits the use of symmetrical electrodes and does not impose any critical dimensional requirements on the electrode system. Thus, one specific object of the invention is to provide such a directional control system in which neither the configuration nor the dimensions of the electrodes, nor the electrode spacing, is critical.

A further object of this invention is to provide an improved glow discharge timekeeping and indicating system having an improved directional control system of the foregoing type which can be fabricated at a relatively low cost. A related object is to provide such a system which can be fabricated in a more compact assembly than most glow discharge timekeeping and indicated systems proposed heretofore.

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Other objects and advantages of the invention will become apparent from the following detailed description and upon reference to the accompanying drawing, in which:

FIG. 1 is a schematic diagram of a glow discharge timekeeping and indicating system embodying the present invention;

FIG. 2 is a schematic diagram illustrating the voltage levels at a series of exemplary electrodes during different states of the operation of the system of FIG. 1; and

FIG. 3 is a pulse diagram illustrating the voltage levels on certain electrodes during the operation of the system of FIG. 1.

While the invention will be described in connection with certain preferred embodiment, it will be understood that it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims.

In order to understand the present invention, the principles of gas discharges must be borne in mind. To obtain a gas discharge, a pair of electrodes are spaced apart in an envelope containing an ionizable gas, usually at low pressure, and an electrical potential is applied across the electrodes. Since gases do not conduct electricity, initially no current will flow between the positively charged electrode (the anode) and the negatively charged electrode (the cathode). However, a gas is subject at all times to bombardment by cosmic rays and other nuclear radiation from natural sources, as a result of which some gas atoms become ionized, i.e., they lose or gain one or more electrons and become positive or negative ions. The positive ions are, of course, attracted to the cathode, and the negative ions are attracted to the anode. If the potential between the cathode and the anode is small or the spacing great, only a very small Townsend or dark discharge current will flow between the cathode and anode. If the voltage across the electrodes is great enough, some positive ions will gain sufiicient energy that, upon hitting the cathode, they release on or more electrons. Furthermore, electrons and negative ions travelling toward the anode may gain sufficient energy to ionize a gas atom upon collision, if the potential and the distance travelled before collision with the gas molecule are great enough. At low potentials or great electrode spacing, the loss of ions and electrons by diffusion to the walls of the vessel and by recombination into neutral atoms, is much more likely than the production of new ions throught the various described collision processes. However, for any given electrode spacing, there is a certain characteristic potential, herein called the breakdown voltage, at which more ions are created by collision processes than are lost by diffusion and recombination. At this point, the current flowing in the discharge increases abruptly and would become infinite if it were not for the external resistance in the circuit. There then exists a region of intense ionization which emits a characteristic flow, ordinarily spaced approximately half a millimeter from the cathode, known as the cathode glow. Ordinarily, the glow will not cover the entire surface of the cathode, the particular area covered being proportional to the current between the electrodes.

If a potential equal to or greater than the breakdown voltage is applied across the electrodes of a gas discharge tube in which no glow is present, a certain amount of time, called the ionization time, in the order of some microseconds, is required for the ionization and thus the current to build up to that limited by the external resistance in the circuit.

If a pair of electrodes are located adjacent to an existing glow discharge, within a few millimeters for example,

the space between the electrodes is partially ionized due to diffusion of electrons and ions from the adjacent glow discharge. This degree of ionization is much greater than that due to natural sources, and reduces the breakdown voltage to the so-called transfer voltage, and this effect can be used to selectively transfer the glow discharge from one cathode to an adjacent electrode. Electrode next to a glowing cathode that have such a reduced breakdown voltage (the transfer voltage) are generally referred to as primed electrodes.

When a glow discharge exists between a cathode and an anode, a characteristic potential will exist therebetween, herein called the maintaining voltage, which again is a characteristic of the gas. In order to maintain a glow discharge, the external circuitry connected to the cathode and anode must be able to supply current to them at the maintaining voltage. If the potential supplied to the cathode and anode is allowed to drop below the maintaining voltage, the glow discharge will terminate, but the cathode will remain primed for the deionization time of the gas, i.e., the time required for most of the ionized atoms to recombine with free electrons. For most gases this time is in the order of some milliseconds and is much larger than the ionization time. For further understanding of the characteristics of such gas discharge devices, reference may be made to such texts as: Action & Swift, Cold Cathode Discharge Tubes, Academic Press, Inc., New York 1963; Rudolf Seeliger, Angewandte Atomphysik, Julius Springer, Berlin 1938; and Leonard B. Loeb, Basic Processes of Gaseous, Electronics, 2nd edition, University of California Press, 1955.

Turning now to the drawing and referring first to FIG. 1, there is shown in schematic form an electronic counting system including a series of electrodes E1 through E12 for use in a timekeeping and display system. In operation, a glow discharge is initiated at one of the electrodes and then stepped along the electrode series in response to electrical input pulses representing repetitive time intervals so that the position of the glow discharge at any given instant provides a visible indication of the pulse count, thereby indicating the time. To provide separate indications of the seconds, minutes, and hours, a plurality of such electrode series may be cascaded, with the electrodes in each series being arranged to correspond to successive positions of conventional clock hands; for example, a plurality of separate electrode series of the type illustrated in FIG. 1 may be arranged in concentric circles in a timepiece structure of the type described in the aforementioned copending applications Ser. No. 524,027 and Ser. No. 705,793. Alternatively, the illustrative system may be used in electronic counting systems which are used for purposes other than timekeeping. Regardless of the particular application, however, the electrodes are always enclosed in a chamber filled with a suitable ionizable gas such as argon or the like. It will be understood that the particular physical structure and geometric arrangement of the electrodes does not form a part of the present invention nor is the invention limited to any particular number of electrodes, the illustrative series of twelve electrodes E1-E12 being shown merely as one example. The particular means of forming the illustrative glow discharge tube and the electrical connections thereto, the particular materials employed therein, and the particular dimensions and configuration thereof do not form a part of the present invention, and specific exemplary embodiments have already been described in detail in the aforementioned copending applications. Such description will not be repeated herein, since reference may be held to the copending applications, particularly Ser. No. 524,027, for a more detailed understanding thereof, and since the present invention is equally applicable to a wide variety of such systems.

As shown in FIG. 1, the electrodes E1-E12 are interconnected via three bus lines I, II, and III to form three electrode groups which are arranged so that each pair of successive electrodes in one group are spaced apart by a pair of electrodes from the other two groups. In the particular arrangement illustrated, this grouping is achieved by connecting electrodes E1, E4, E7 and E10 to bus line I (electrode group I); electrodes E2, E5, E8 and E11 to bus line II (electrode group II); and electrodes E3, E6, E9 and E12 to bus line III (electrode group III). For the purpose of applying electrical input signals to the three electrode groups, the three bus lines I, II and III are connected to two electrical input terminals A and B, line I being connected to terminal A and lines 1 1 and III being connected to terminal B. The terminals A and B, in turn, are connected to electrical control means for applying a transfer potential alternatively to first and second cathode groups in the electrode series in response to electrical input signals, representing predetermined time intervals in a timekeeping system, so as to repetitively step a glow discharge along the electrode series and thereby count the input signals while providing a continual visible indication of the instantaneous count or time.

The electrical input signals representing repetitive time intervals to be counted by the system of FIG. 1 may be derived from a conventional 60-cycle A-C supply connected to input terminals 20 of a conventional pulseshaping circuit 21 which produces a pulse train for ap plication to a flip flop 22. In response to the input pulses from the pulse-shaper 21, the flip flop 22 produces output pulses for triggering an electronic switching circuit 23. Thus, the illustrative timekeeping system is of the synchronous type, since it relies on the oscillations of the available power line signal as the timekeeping standard. In this type of system, an additional electrode series may be included in the system for the purpose of dividing the 60-c.p.s. line frequency to produce input pulses to the first series of display electrodes at a frequency of one pulse per second. However, it is to be understood that this invention is not limited to synchronous systems, but rather is equally applicable to systems using other timekeeping standards, such as self-contained electrical or electromechanical oscillators, for example.

For the purpose of stepping a glow discharge along electrode series E1*El2, the electrode switching circuit 23 responds to output signals from the flip flop 22 to apply a transfer potential alternately to the two input terminals A and B. Thus, in the illustrative circuit, a source of transfer potential V is operatively connected to the electrode series, and the electronic switching circuit 23 responds to the signals from the flip flop 22 to apply the transfer potential alternately to the first and second input terminals A and B. More particularly, as the flip flop 22 is switched back and forth between its two stable states in response to the triggering pulses from the pulse-shaping circuit 21, a square wave output is applied to the switching circuit 23 to turn the two transistors Q1 and Q2 therein alternately on and off, thereby controlling the voltage levels at the two terminals A and B.

When the flip flop 22 is in one state, the transistor Q1 is saturated by the flip flop output signal applied thereto via line 24 and resistor R1, and the transistor Q2 is cut off, so that the terminal A is grounded and the terminal B is at the transfer potential. In this operative state, a glow discharge can be transferred to one of the electrodes connected to the terminal A, and at least one of the electrodes connected to terminal B and located adjacent to the glowing electrode functions as an anode. The glow discharge current path in this condition is from V through the resistor R4, through the anode or anodes into the glowing cathode, and finally through the saturated transistor Q1 to ground. This condition is maintained, with the cathode continuously glowing, until the next pulse from the pulseshaping circuit 21 switches the flip flop 22 to its other stable state, whereupon the conditions of the transistors Q1, Q2 are reversed. That is, the transistor Q1 is cut off,

and the transistor Q2 is saturated by the flip flop output signal applied thereto via line 25 and the resistor R2, so that the terminal A is at the transfer potential, and the terminal B is grounded. In this operative state, a glow discharge can be transferred to one of the electrodes connected to terminal B, and at least one of the electrodes connected to terminal A and located adjacent to the glowing electrode functions as an anode. The glow discharge current path in this condition is from V through resistor R3, through the anode or anodes into the glowing cathode, and finally through the saturated transistor Q2 to ground.

In accordance with the present invention, two of the three electrode groups are operatively connected to the control means to form first and second display cathode groups, with the glow discharge being transferred repetitively between successive cathodes therein, and the third electrode group is operatively associated with the display cathode groups and the control means to automatically direct the repetitive glow discharge transfers in a predetermined direction along the electrode series. Moreover, the three electrode groups and the control means are interconnected in such a way that at least one of the electrodes adjacent the glowing display cathode always serves as the anode, so that there is no need for a permanent anode in the counting system. Thus, in the illustrative embodiment, the two display cathode groups are electrode groups I and III which are connected to the input terminals A and B, respectively, and the switching circuit 23 applies the transfer potential alternately to the two input terminals A and B so as to repetitively transfer the glow discharge between successive electrodes in the two groups I and III.

In keeping with the invention, electrode group II in the illustrative system is operatively associated with the cathode groups I and III in such a way that the glow discharge will always be transferred from left to right as viewed in FIG. 1. The operation of electrode group II to provide the desired directional control will be more clearly understood by reference to FIG. 2, which is a schematic representation of the electrical conditions of the various electrodes E1E12 in three different operative states A, B and C. Each adjacent pair of upwardly and downwardly extending arrows in FIG. 2 indicates that the transfer potential is applied across that particular pair of electrodes via terminals A and B, and each black dot on the zero reference line indicates that the electrode corresponding thereto is at floating potential. The lines radiating from one of the downwardly extending arrows in each operative state A, B, C indicates that that particular electrode is glowing during that particular operative state, and the arcuate broken line extending between the glowing ar row and an adjacent arrow indicates the primary path of the glow discharge current.

In the operative state represented by line A in FIG. 2, the transfer potential is applied to terminal A so that electrode group I functions as the anode group, electrode group III functions as the display cathode group, and electrode group II is at floating potential. Returning to FIG. 1 for a moment, although electrode groups II and III are connected to the same input terminal B, a diode D1 blocks current flow into the electrodes of group II from adjacent electrodes, so only the electrodes of group III are capable of serving as display cathodes. The particular electrode that is glowing in the operative state illustrated in line A of FIG. 2 is electrode E3, and the primary path of the glow discharge current is from electrode E4 in group I, serving as the anode, into electrode E3 in group III, serving as the display cathode. Electrode E1 in group I may be supplying a very small portion of the discharge current, but there is a definite asymmetrical distribution of both the discharge current and the charge distribution with respect to the glowing cathode E3, with the major portion thereof being between the cathode E3 and the anode E4. Since electrodes E2 and E4 are directly adjacent the glowing electrode E3, they are most heavily primed, and electrodes E1 and E5 are primed to a lesser degree.

Line B in FIG. 2 represents the electrical conditions of the electrodes after the first reversal of potential, i.e., after the transfer potential has been switched from in put terminal A to input terminal B. Electrode group II now functions as the anode group, and electrode group I functions as the display cathode group, with diode D2 blocking current flow from terminal B into the electrodes of group III so that electrode group III is at floating potential. It can thus be seen that the glow discharge must be transferred to one of the electrodes E1, E4, E7 or E10 (group I) and since electrode E4 is the closest of the four electrodes to the previously glowing electrode E3, and thus was the most heavily primed in line A, the glow discharge will obviously be transferred to electrode E4. Any priming of electrode E1 in state A was considerably smaller than that of electrode E4, and electrode E1 is also farther removed from the previously glowing electrode E3 than electrode E4. As illustrated by the arcuate broken line in line B, the primary glow discharge current path in this second operative state is from electrode E5, the anode, into electrode E4, the cathode.

Line C in FIG. 2 illustrates the electrical conditions of the various electrodes after another reversal of potential, i.e., the transfer potential is again applied to terminal A. As in the case of line A, electrode group I functions as the anode group, electrode group III functions as the display cathode group, and electrode group II is at floating potential due to the blocking action of diode D1. Thus, the glow discharge must be transferred back to one of the group III electrodes E3, E6, and E9 and E12. In order to provide a clear understanding of the glow discharge transfer effected by the transition from line B to line C, wave forms illustrating the voltage levels at the two input terminals A and B during successive glow discharge transfers are shown in FIG. 3. Just prior to time 0, the potential V is applied to terminal B (V and discharge current flows between electrodes E5 and E4 as illustrated in line B of FIG. 2. When the potential V is switched to terminal A at time 0, the sharp voltage transition from time 0 to T causes the capacitor C1 (FIG. 1) to temporarily short circuit the diode D1, so there is a short time period (0 to T when the electrodes of group II, including electrode E5, can function as temporary cathodes. Consequently, in the transition from the operative state of line B in FIG. 2 to the operative state of line C, electrode E5 becomes a glowing cathode for a brief period and then, because it has an effective resistance in series with it that changes from a low to a high value, immediately extinguishes and transfers its glow to the adjacent group III electrode E6 which becomes the glowing cathode for the time period T to T At time T the potential V is switched back to terminal A, thereby transferring the glow discharge to electrode E7 for the time period T to T in the same manner described previously.

As can be seen from the foregoing description, the electrodes of group I function alternately as anodes and display cathodes in response to the switching of the transfer potential between terminals A and B; the electrodes of group II function alternately as anodes and temporary cathodes; and the electrodes of group III function only as display cathodes. Thus, only two thirds of the electrodes function as glowing cathodes, but by including the third electrode group in accordance with this invention, there is no need for a permanent anode in the glow discharge system, and at the same time the direction of the glow discharge transfer is continuously and reliably controlled without requiring asymmetrical electrodes and without any critical dimensional requirements. Consequently, the system can be fabricated at a relatively low cost, and in a compact assembly.

While the invention has been described with specific reference to one preferred embodiment thereof, it will be appreciated that the invention is applicable to a number of different modifications of the illustrative embodiment. For example, the direction of the glow dischrage transfer may be reversed by simply reversing the diodes D1, D2 and connecting the capacitor C1 across diode D2 rather than diode D1. Another possible modification is to arrange the electrodes in four groups with two groups connected to each input terminal in the same manner as groups II and III described above, but eliminating the diode D2; in this case, each electrode group functions either as a display cathode group or as an anode-temporary cathode group. Various modifications may also be made in the circuits between the input terminals and the various electrode groups; for example, the addition of a resistor connected across the capacitor C1 will increase the time interval during which the electrodes associated therewith function as temporary cathodes.

As can be seen from the foregoing detailed description, this invention provides an improved glow discharge time keeping and indicating system having an improved d1- rectional control system for controlling the direction of movement of the glow discharge as it is stepped along a series of electrodes. The improved directional control system permits the use of symmetrical electrodes and does not impose any critical dimensional requirements on the electrode system, and neither the configuration nor the dimensions of the electrodes, nor the electrode spacing, is critical. Moreover, the direction of the glow discharge movement along the electrode series can be readily reversed by making a simple change in the control circuit. In addition, the improved system can be efficiently fabricated at a low cost, and in a compact assembly.

I claim as my invention:

1. An improved timekeeping and indicating system comprising the combination of a glow discharge tube containing an ionizable gas and a series of spaced internal electrodes for counting successive time intervals in response to electrical input signals representingsaid time intervals, first electrical input means operatively connected to a first group of said electrodes and interconnecting the same to form a first display cathode group, second electrical input means operatively connected to a second group of said electrodes and interconnecting the same to form a second display cathode group, one of the cathodes of said first group being located between each pair of successive cathodes of said second group, and one of the cathodes of said second group being located between each pair of successive cathodes of said first group, direction control means including a third group of said electrodes interconnected to form a control electrode group connected to one of said input means with one of the electrodes of said third group being located between each pair of successive electrodes in at least one of said display cathode groups, electrical control means operatively connected to said first and second electrical input means for applying a transfer potential for said glow discharge tube alternately to said first and second input means in response to said electrical input signals so as to repetitively transfer the glow discharge between successive cathodes of said first and second display cathode groups in synchronism with said electrical input signals, said control electrode group being operatively associated with said display cathode groups to automatically direct the repetitively glow discharge transfers in a predetermined direction along the electrode series.

2. An improved timekeeping and indicating system as set forth in claim 1 in which a cathode from each of said display cathode groups is located between each pair of successive electrodes in said control electrode group.

3. An improved timekeeping and indicating system as set forth in claim 1 in which said second electrical input means is operatively connected to said control electrode group as well as said second cathode group, and said electrical control means includes means for applying said 8 transfer potential alternately across 1) said first and second cathode groups and (2) said first cathode group and said control electrode group.

4. An improved timekeeping and indicating system as set forth in claim 1 in which said electrode groups are responsive to the application of said transfer potential to said first and second input means so that said first group functions alternately as a display cathode group and an anode group, said second group functions as as display cathode group when said first group functions as an anode group, and said third group functions as an anode group when said first group functions as a display cathode group, said third group also functioning as a temporary cathode during the transition of said first group from a cathode function to an anode function.

5. An improved timekeeping and indicating system comprising the combination of a glow discharge tube containing an ionizable gas and a series of spaced internal electrodes for counting successive time intervals in response to electrical input signals representing said time intervals, first and second electrical input means operatively connected to said electrode series, electrical control means operatively connected to said first and second input means for applying a transfer potential for said glow discharge tube alternately to said first and second electrical input means, a first group of said electrodes being operatively connected to said first input means for providing an anode for a glow discharge in response to application of said transfer potential to said first input means and for providing a display cathode in response to application of said transfer potential to said second input means, a second group of said electrodes being operatively connected to said second input means for providing a display cathode in response to the application of said transfer potential to said first input means, one of the electrodes of said second group being located between each pair of successive electrodes of said first group, and a third group of said electrodes being operatively connected to said second input means for providing an anode in response to application of said transfer potential to said second input means and for providing a temporary cathode for a brief interval after the application of said transfer potential to said first input means, one of the electrodes of said third group being located between each pair of successive pairs of electrodes of said first and second groups.

6. An improved timekeeping and indicating system as set forth in claim 5 wherein said second and third electrode groups are operatively connected to said second input means via oppositely facing diodes so that said second group functions as a cathode and said third group functions as an anode, and a capacitor is connected across the diode associated with said third group for shunting the diode during a sharp voltage transition immediately following the application of said transfer potential to said first input means whereby said third group functions as a temporary cathode.

7. An improved counting system comprising the combination of a glow discharge tube containing an ionizable gas and a series of spaced internal electrodes for counting successive electrical input signals, first electrical input means operatively connected to a first group of said electrodes and interconnecting the same to form a first display cathode group, second electrical input means operatively connected to a second group of said electrodes and interconnecting the same to form a second display cathode group, one of the cathodes of said first group being located between each pair of successive cathodes of said second group, and one of the cathodes of said second group being located between each pair of successive cathodes of said first group, direction control means including a third group of said electrodes interconnected to form a control electrode group connected to one of said input means with one of the electrodes of said third group being located between each pair of successive electrodes in at least one of said display cathode groups, electrical control means operatively connected to said first and second electrical input means for applying a transfer potential for said glow discharge tube alternately to said first and second input means in response to said electrical input signals so as to repetitively transfer the glow discharge between successive cathodes of said first and second display cathode groups in synchronism with said electrical input signals, said control electrode group being operatively associated with said display cathode groups to automatically direct the repetitive glow discharge transfers in a predetermined direction along the electrode series.

8. An improved counting system as set forth in claim 7 in which a cathode from each of said display cathode groups is located between each pair of successive electrodes in said control electrode group.

9. An improved counting system as set forth in claim 7 in which said second electrical input means is operatively connected to said control electrode group as well as said second cathode group, and said electrical control means includes means for applying said transfer potential alternatively across (1) said first and second cathode groups and (2) said first cathode group and said control electrode group.

10. An improved counting system as set forth in claim 7 in which said electrode groups are responsive to the application of said transfer potential to said first and second input means so that said first group functions alternately as a display cathode group and an anode group, said second group functions as a display cathode group when said first group functions as an anode group, and said third group functions as an anode group when said first group functions as a display cathode group, said third group also functioning as a temporary cathode during the transition of said first group from a cathode function to an anode function.

11. An improved counting system comprising the combination of a glow discharge tube containing an ionizable gas and a series of spaced internal electrodes for counting successive electrical input signals, first and second electrical input means operatively connected to said electrode series, electrical control means operatively connected to said first and second input means for applying a transfer potential for said glow discharge tube alternately to said first and second potential input means, a first group of said electrodes being operatively connected to said first input means for providing an anode for a glow discharge in response to application of said transfer potential to said first input means and for providing a display cathode in response to application of said transfer potential to said second input means, a second group of said electrodes being operatively connected to said second input means for providing a display cathode in response to the application of said transfer potential to said first input means, one of the electrodes of said second group being located between each pair of successive electrodes of said first group, and a third group of said electrodes being operatively connected to said second input means for providing an anode in response to application of said transfer potential to said second input means and for providing a temporary cathode for a brief interval after the application of said transfer potential to said first input means, one of the electrodes of said third group being located between each pair of successive pairs of electrodes of said first and second groups.

12. An improved counting system as set forth in claim 11 wherein said second and third electrode groups are operatively connected to said second input means via oppositely facing diodes so that said second group functions as a cathode and said third group functions as an anode, and a capacitor is connected across the diode associated with said third group for shunting the diode during a sharp voltage transition immediately following the application of said transfer potential to said first input means whereby said third group functions as a temporary cathode.

13. An improved counting system as set forth in claim 11 which includes a fourth group of said electrodes operatively connected to said first input means for performing the anode function of said first group of electrodes in response to application of said transfer potential to said first input means and for providing a temporary cathode for a brief interval after the application of said transfer potential to said second input means, one of the electrodes of said fourth group being located between each pair of successive electrodes of said first and second groups.

References Cited UNITED STATES PATENTS 3,098,946 7/1963 Meyers 3l584.6 3,213,374 10/1965 Hawley 315-846 X 3,227,922 1/1966 Glaser et al. 3l5-135 3,456,152 7/1969 Anderson 315-846 3,466,498 9/1969 Koster et al. 3l5--84.6

JAMES W. LAWRENCE, Primary Examiner E. R. LAROCHE, Assistant Examiner US. Cl. X.R. 3l58.5

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