US3780341A

US3780341A - Circuit for operating multiple position display devices

Info

Publication number: US3780341A
Application number: US00332162A
Authority: US
Inventors: G Holz; F Dieterman
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1973-02-13
Filing date: 1973-02-13
Publication date: 1973-12-18
Anticipated expiration: 1990-12-18

Abstract

The circuit of the invention is adapted for operating multipleposition display devices having several groups of display cathode segments or elements positioned in a row, with corresponding segments in each group connected in common, an anode electrode associated with each group of display segments, and an auxiliary electrode being common to and electrically isolating the groups of segments. The cathode segments, together with an anode, can be selectively energized to display a character at any desired cathode group or position and the auxiliary electrode inhibits electrical discharge between the cathode segments and any other than the associated anode. The circuit includes a separate driver circuit for each cathode and for each anode and a circuit for biasing the ''''OFF'''' cathodes, the ''''OFF'''' anodes, and the auxiliary screen electrode a predetermined difference in potential from the anode supply voltage and independent of the amount of current conducted by the cathodes or by the auxiliary electrode itself.

Description

United States Patent [191 Holz et al.

[ 51 Dec. 18, 1973 CIRCUIT FOR OPERATING MULTIPLE POSITION DISPLAY DEVICES Inventors: George Ernest Holz, North Plainfield; Felix Dieterman, Piscataway, both of NJ.

Primary ExaminerCarl D. Quarforth Assistant Examiner.l. M. Potenza Attorney-George L. Kensinger et a1.

[ 5 7 ABSTRACT The circuit of the invention is adapted for operating multiple-position display devices having several groups of display cathode segments or elements positioned in a row, with corresponding segments in each group connected in common, an anode electrode associated with each group of display segments, and an auxiliary electrode being common to and electrically isolating the groups of segments. The cathode segments, together with an anode, can be selectively energized to display a character at any desired cathode group or position and the auxiliary electrode inhibits electrical discharge between the cathode segments and any other than the associated anode. The circuit includes a separate driver circuit for each cathode and for each anode and a circuit for biasing the OFF cathodes, the OFF anodes, and the auxiliary screen electrode a predetermined difference in potential from the anode supply voltage and independent of the amount of current conducted by the cathodes or by the auxiliary electrode itself.

20 Claims, 3 Drawing Figures r34- 41 3; 51 36 4 1 5 ,i .L J: Ebb ,l;| 1- 1] I H21 AF 12 140 43 1 0 53,1 (03 w, I12 :I :Z/ 111 2 7 113 25 PAIENIED EM 3.780.341

SHEEI 1 i 2 2 0 .42 41 45 I40 52 5| 5 I (02. (pl QB O IN'VENTOR. GEORGE E. HOLZ BY FE'LlX D1ETERMHN QTTORNEY CIRCUIT FOR OPERATING MULTIPLE POSITION DISPLAY DEVICES This application is a continuation of Ser. No. 85,622,-

filed Oct. 30, 1970, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to apparatus for operating glow discharge display devices having multiple display positions. More particularly, the invention relates to circuitry for operating multiple-position gas discharge devices having segmented cathode electrodes.

Several display devices have been developed recently having a plurality of groups of cathode segments positioned in a row in either a tube or a flat panel. These devices generally include electrical connections between the corresponding cathode segments, and an anode for each display position to enable a timesharing mode of operation.

In operating such devices, the cathode segments are selectively energized, together with an anode, to provide an electrical discharge at a selected group of cathode segments to display a desired number or symbol. The electrical discharge ionizes the adjacent gas molecules and results in cathode glow discharge on the selected segments which display the desired character.

, The electrical discharge between the selected groups of display segments and the associated anodes must be isolated from affecting the ON or OFF state of the other groups of display segments and their respective anodes. When one group of electrode segments is glowing and representing a character, however, undesirable spurious glow sometimes develops in an adjacent group of electrodes or in a path or positive column arising between them.

This spurious discharge and the resultant spurious glow can be overcome by providing an auxiliary electrode biased inter intermediate the cathode and anode potential as described and claimed in Harvey, et al., U.S. Pat. application Ser. No. 78,045 filed Oct. 5, 1970, and now abandoned. The auxiliary electrode, however, conducts current from the ionized gas in the device which raises its potential in proportion to the number of cathode segments which are energized.

The potential on the auxiliary electrode, however, must be kept sufficiently more negative than the ON anode in order to prevent spurious cathode glow but without initiating cathode glow on the auxiliary electrode itself. One level of bias on the auxiliary electrode is sometimes ineffective to prevent spurious discharge both when only one or two segments are energized and also when all or most of the cathodes are energized. This difficulty becomes especially pronounced when variations in tubes or panels result in them having different operating characteristics.

Another difficulty experienced in operating such display devices is an unsuitably narrow range or tolerance to variation in the anode supply voltage and in the auxiliary electrode bias voltage for effective spurious glow suppression.

SUMMARY OF THE INVENTION Accordingly, an object of this invention is to improve spurious glow supporession in multiple-position display devices having commonly connected cathode electrodes.

Another object of the invention is to enlarge the range or tolerance for bias levels in multiple-position gas discharge display devices having auxiliary electrodes for spurious glow suppression.

A further object of the invention is to reduce the complexity and cost of systems for operating display devices having spurious glow suppression electrodes.

According to the invention a circuit for operating multiple-position display devices includes voltage reference elements or devices coupled for establishing predetermined potential differences between the anode supply voltage and the unenergized cathodes and anodes and the auxiliary electrode. It also includes an impedance coupled to the auxiliary electrode and to its voltage reference element or device for conducting the leakage current that it collects from ON anodes, without affecting the bias potential on it.

DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a segmented cathode display tube having individual anodes and an overlying auxiliary electrode;

FIG. 2 is an elevational view of a longitudinal section of the display tube or panel of FIG. 1; and

FIG. 3 is an electrical schematic diagram of a preferred embodiment of the circuit of applicants invention for operating such a device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principles of the invention are particularly applicable to the type of display device described and claimed in copending Harvey, et al., U.S. Pat. application Ser. No. 78,045, filed Oct. 5, 1970. Some of the features of such a tube 10 are shown schematically in FIGS. 1 and 2 of three representative display positions. A plurality of groups of cathode segments 41-47, 51-57, 61-67, etc. are connected to corresponding conductors 21-27 which are insulated from each other and isolated from glow, and an

anode electrode

140, 150, 160, etc. is provided for each group. The anodes in FIG. 1 are each shown as a ring surrounding its group of cathodes, but it may be a screen covering the associated cathode group, or it may take any other shape. In addition, the device includes a screen electrode 230 which is disposed above the groups; of cathodes and anodes and is electrically associated with them all and top and bottom insulating plates 200 and 20, respectively.

Briefly, in operation of the tube shown in FIGS. 1 and 2, drive signals are applied to the cathodes via

conductors

21, 22, 27 in accordance with the input information. Simultaneously, each of the anodes is energized in turn or in any other desired order or sequence via

leads

34, 35, 36, etc. to cause the cathodes in its group to exhibit cathode glow. Screen electrode 230 carries a suitable potential applied to lead 235 for preventing spurious glow between adjacent display positions.

The preferred embodiment of the circuit of the invention is illustrated in FIG. 3 and display device 10 is shown schematically.

Display cathode segments

41, 51 and 61 are connected to conductor 21 which is connected to the collector of cathode driver transistor 121. Display cathode segments 42, S2, and 62 are connected to conductor 22 which is connected to the collector of driver transistor 122. The

cathode segments

43, 53, and 63 are connected to conductor 23 which is connected to the collector of cathode drive 123.

Currentlimiting resistors

131, 132 and 133 are connected between the emitters of

transistors

121, 122 and 123, respectively, and reference potential terminal 120. The base electrodes of

cathode driver transistors

121, 122 and 123 are connected to

input terminals

221, 222, 223, respectively, for receiving positive-going information signals.

Anode lead 34 of anode 140 is connected to the collector of anode drive transistor 240. Anode lead 35 of anode 150 is connected to the collector of transistor switch 250. Anode lead 36 of anode 160 is connected to the collector of anode switch 260. The emitter electrodes of anode transistor switches 240-260 are connected to anode supply terminal 12 and their base electrodes are connected to

anode control terminals

245, 255 and 265 by current-limiting

resistors

241, 251 and 261, respectively, for receiving negative-going control signals.

The cathode segments are initially biased by pull-

up resistors

111, 112 and 113 connected at one end to the collectors of

cathode driver transistors

121, 122 and 123, respectively. The other ends of resistors 111-113 are connected at circuit junction 15 to the anode of Zener diode 14, the cathode of which is connected to anode supply terminal 12. Anodes 140-160 are initially biased by resistors 340-360 also connected at junction 15 to the anode of Zener diode 14. This establishes a fixed potential difference between the anode supply voltage Ebb and the unenergized cathodes and anodes, regardless of the specific value of Ebb or of fluctuation in it.

The electrode terminal 235 of auxiliary electrode 230 is connected at circuit junction 17 to the anode of Zener diode 16 and to one end of resistor 18. The cathode of Zener diode 16 is connected at junction 15 to the anode of reference diode 14 and the other end of resistor 18 is connected to reference potential terminal 120. This establishes a constant difference in potential between the auxiliary electrode 230 and the anode supply potential Ebb and auxiliary electrode current is conducted by resistor 18 to source Ek to be connected to terminal 120.

Reference diodes

14 and 16 may alternatively be any other type of voltage regulating devices or may be voltage sources. Resistor 18 may be replaced with any other current-limiting impedance, either an active or passive device.

In operation of the device, the auxiliary electrode 230 conducts a leakage current from whichever anode electrode 140-160 is energized to resistor 18 and the source connected to terminal 120. If this leakage current increases as more cathodes are energized, for example, the current through

Zener reference diodes

14 and 16 merely decreases, without affecting the potential on either the OFF cathodes or anodes or on the auxiliary electrode itself. As the leakage current of auxiliary electrode 230 decreases due to decreased glow discharge, for example, the Zener diode current simply increases, also without affecting the bias potentials on the electrodes of the device.

The maintenance of the voltage difference between auxiliary electrode 230 and the anode supply voltage prevents the auxiliary electrode from becoming too greatly cathodic (too negative with respect to an energized anode) which may cause it to develop cathode glow itself. It also prevents auxiliary electrode 230 from rising in potential closer to the ON" anode potential as a larger number of cathode segments are energized,

and thus lose its spurious glow suppression effectiveness.

In the operation of display device 10 to display a plurality of numerals, relatively negative information signals are applied to one or

more cathode conductors

21, 22, 23 27 from a suitable data source, and a generally positive potential may be applied to the first anode 140. The selected ones of cathode segments 41-47 which are thus energized, glow and display a first numeral at the first display position. A second group of information signals is applied to selected cathode conductors 21-27 and the second anode is energized, and a second numeral is displayed by the selected ones of cathode segments 51-57 at the second display position. In the same way, the successive application of different information signals to selected cathode conductors and to the anodes, in turn, causes a character to be displayed at each character position. If this sequence is repeated through the display device from one end to the other at a sufficiently high rate, a stationary but changeable series of numerals can be displayed in the panel, one at each character position. As the cycling operation is carried out, if the information signals on the cathode conductors change, then the characters at the respective display positions also change.

The above-described mode of operation utilizes sequential time-shared driving of

anode electrodes

140, 150, 160, etc., of the device. This sequentially energizes the successive display positions along the device. Another mode of operation involves time-shared driving of the cathode electrode segments. The

anode electrodes

140, 150, 160, etc., are selectively energized from a data source, for example, and cathode connectors 21-27 are energized successively for sequencing the display. The energization of the

anode electrodes

140, 150, 160, etc., may be changed as desired for varying the pattern of the display. The anodes and cathodes may be energized in any other desired order, also, depending upon the desired mode of display.

Although the preferred embodiment of the invention has been described in detail, it should be understood that the present disclosure has been by way of example only. Many modifications and variations of the invention are possible in light of the above teachings. It is, therefore, to be understood that the invention may be practiced otherwise than as specifically disclosed.

What We Claim is:

l. A character display circuit comprising an envelope containing an ionizable gas,

an anode and a plurality of cathodes within said envelope, each of said cathodes having the shape of a segment of a character to be displayed,

circuit means for establishing a glow potential between said anode and different combinations of said cathodes for causing said different combinations of said cathodes to glow and thereby display different characters,

said circuit means including a plurality of cathode drivers, one connected to each of said cathodes, and means for selectively energizing said cathode drivers to render different combinations of their connected cathodes glowing,

an auxiliary electrode in contact with the ionizable gas and in operative relation with said anode and cathodes,

an anode supply voltage terminal and circuit means connected between said terminal and said anode,

bias circuit means for said anode and said cathodes including a voltage reference device connected electrically from said anode supply voltage terminal and having a second terminal to establish a predetermined voltage on said second terminal relative to the voltage on the anode supply terminal, and a plurality of impedance means, one connected from said second terminal to said anode and the others each connected from said second terminal to a different one of said cathodes, and

second bias circuit means for establishing a bias voltage on said auxiliary electrode comprising a second voltage reference device connected between said anode supply terminal and a third terminal to establish a voltage thereon lower than the voltage on said second terminal, and circuit means connecting said auxiliary electrode to said third terminal.

2. A character display device as in claim 1 wherein the second voltage reference device is connected between said second and third terminals, and it is thus connected to the anode supply voltage terminal through said first reference voltage device.

3. A character display circuit as in claim 2 further including a cathode reference terminal,

a plurality of current-limiting impedance devices,

one connected from said cathode reference terminal to each of said cathode drivers, and

a further impedance device connected between said cathode reference terminal and said third terminal.

4. A character display circuit comprising an envelope containing an ionizable gas,

circuit means for establishing a glow potential between said anode and different combinations of said cathodes for causing said different combinations of cathodes to glow and thereby display different characters,

said circuit means including'a plurality of cathode drivers, one connected to each of said cathodes, and means for selectively energizing said cathode drivers to render different combinations of their connected cathodes glowing,

bias circuit means for said anode and cathodes including a first terminal at a predetermined voltage, an impedance'connected from said first terminal to said anode, and a plurality of additional impedances each connected from said first terminal to a different one of said cathodes, and

second bias circuit means for said auxiliary electrode including a voltage reference device connected electrically from said first terminal to a second terminal, and circuit means connecting said auxiliary electrode to said second terminal.

5. A character display circuit as in claim 4 further including 6. A character display circuit for displaying any one of a plurality of characters in each of a plurality of sideby-side character positions, comprising a plurality of cathode conductors each electrically connected to one of the cathodes in each character position,

a plurality of cathode drivers, each connected to one of said cathode conductors, for energizing said cathodes selectively in response to a first set of input signals,

anode selection circuit means for selectively energizing said anodes, in synchronism with the selective energization of said cathodes, in response to a second set of input signals, for displaying selected characters in each of said character positions,

an auxiliary electrode in the gaseous atmosphere associated with each character position, the current therethrough being a function of the number of cathodes which are glowing,

an anode voltage supply terminal, with said anode selection circuit means connected between said terminal and each of said anodes,

anode bias circuit means including a second terminal, first voltage reference means including a voltage reference device connected from said anode supply voltage to said second terminal, and a plurality of impedance devices, each connected from said second terminal to one of said anodes, and

an auxiliary bias circuit means including a second voltage reference means connected from said anode supply voltage terminal to a third terminal and circuit means connecting said auxiliary electrode to said third terminal,

7. A character display circuit as in claim 6 wherein said second voltage reference means includes a voltage reference device connected from the second to the third terminal.

8. A character display circuit as in claim 6 further including a ctahode bias circuit including a further plurality of impedance devices, each connected from said second terminal to one of said cathode conductors.

9. A character display circuit for displaying any one of a plurality of characters in each of a plurality of sideby-side character positions, comprising a plurality of anodes, one in each of said character positions,

a plurality of groups of cathodes, each group being associated with one of said anodes and being located in one of said character positions, each of the cathodes having the shape of a segment of one of the characters to be displayed,

each of said anodes and its associated cathodes being disposed in an ionizable gas atmosphere capable of sustaining cathode glow discharge,

a plurality of cathode conductors each electrically connected to one of the cathodes in each character position,

a plurality of cathode drivers, each connected to one of said cathode conductors, for energizing said cathodes selectively in responseo to a first set of input signals,

anode selection circuit means for selectively eeergizing said anodes, in synchronism with the selective energization of said cathodes, in response to a second set of input signals, for displaying selected characters in each of said character positions,

an auxiliary electrode in the gaseous atmosphere associated with each character position,

anode bias circuit means including a first terminal at a predetermined potential and a plurality of impedance devices each connected from said terminal to one of said anodes, and

an auxiliary electrode bias circuit including a voltage reference device connected electrically from said first terminal to said auxiliary electrode.

10. A character display circuit as in claim 9 further comprising a cathode bias circuit including a further plurality of impedance devices each connected from said first terminals to one of said cathode conductors.

11. A character display circuit as in claim 9 further comprising an anode supply voltage terminal, with said anode selection circuit means electrically connecting said terminal to each of said anodes, and

a voltage reference device electrically connected from said anode supply voltage terminal to said first terminal.

12. A character display circuit for displaying any one of a plurality of characters in a plurality of side-by-side character positions, comprising an envelope formed of a front plate with a viewing window and a rear plate, said plates being sealed together along a predetermined perimeter surrounding the side-by-side character positions to establish a gas tight enclosure,

an ionizable gas within said enclosure at a pressure capable of sustaining a cathode glow discharge,

a plurality of anodes, one at each of said character positions within said envelope,

a plurality of groups of cathodes, each such group being associated with one of said anodes and being located in one of said character positions, each of the cathodes having the shape of a segment of one of the characters to be displayed,

a plurality of elongated conductors extending within said envelope, each electrically connected to one of the cathodes in each character position, and each connected electrically to a terminal outside said envelope for connection to an external circuit,

insulating material separating each of said conductors from all of the cathodes except the cathode in each character position to which it is connected,

anode selection means for energizing said anodes sequentially and cathode selection means for selectively energizing different combinations of said cathode conductors sequentially, in synchronism with sequential energization of the anodes, to form a side-by-side character display along said character positions,

an auxiliary electrode associated with each of said character positions and being in operative relation with the anode and the cathodes in each such position, anode bias circuit means including a first terminal at a predetermined potential and a plurality of impedance means each connected electrically from said first terminal to a different one of said anodes,

cathode bias circuit means including a further plurality of impedance means each connected electrically from said first terminal to a different one of said cathodes, and

a voltage reference device connected electrically from said first terminal to said auxiliary electrode.

13. A character display circuit as in claim 12 wherein the auxiliary electrode has a portion thereof located between the anode and cathodes in each character position and those of the next adjacent character position,

further including an anode voltage supply terminal connected through said anode selection circuit to each of said anodes and a further reference voltage device connected from said anode voltage supply terminal to bias the auxiliary electrode to a predetermined voltage below said anode supply voltage for isolating the anode and cathodes of each character position from those of all of the other character positions.

14. A system for operating multiple-position display devices having a plurality of groups of cathode elements situated in an ionizable medium, an anode associated with each of the groups, and an auxiliary electrode that is common to all of the groups and shields them from each other, comprising means coupled to each of the cathode elements for driving them selectively in response to a first set of input signals,

means coupled to each of the anodes for energizing them selectively in response to a second set of input signals,

voltage supply terminals connected to the cathode driving means and to the anode energizing means for receiving operating potential for them,

voltage reference means coupled between the auxiliary electrode and the voltage supply terminal of the anode energizing means, and

impedance means coupled between the voltage reference means and the cathode driver voltage supply terminal.

15. The display system of claim 14 further comprising resistance means also coupling each of the cathode elements and each of the anodes to said voltage reference means. I

16. The display system of claim 15 wherein the volt age reference means comprises a pair of voltage reference devices connected in electrical series with said impedance means, and said resistance means couples the anodes and cathode elements to the junction of the voltage reference devices.

17. The display system of claim 14 wherein the groups of cathode elements comprise a plurality of cathodes in the form of segments of a character to be displayed, with corresponding segments of the groups being interconnected and the auxiliary electrode electrically shields the groups of segments from each other for preventing spurious glow discharge in the device.

18. The display system of claim 17 wherein the anode energizing means comprises a voltage switch for each anode, and the anodes and cathode elements are each 20. The display system of claim 18 wherein the anode drivers are connected to a source of information signals to control the pattern to be displayed and the cathode drivers are connected to a source of position control signals to select the position for each display pattern in the device.

Claims

1. A character display circuit comprising an envelope containing an ionizable gas, an anode and a plurality of cathodes within said envelope, each of said cathodes having the shape of a segment of a character to be displayed, circuit means for establishing a glow potential between said anode and different combinations of said cathodes for causing said different combinations of said cathodes to glow and thereby display different characters, said circuit means including a plurality of cathode drivers, one connected to each of said cathodes, and means for selectively energizing said cathode drivers to render different combinations of their connected cathodes glowing, an auxiliary electrode in contact with the ionizable gas and in operative relation with said anode and cathodes, an anode supply voltage terminal and circuit means connected between said terminal and said anode, bias circuit means for said anode and said cathodes including a voltage reference device connected electrically from said anode supply voltage terminal and having a second terminal to establish a predetermined voltage on said second terminal relative to the voltage on the anode supply terminal, and a plurality of impedance means, one connected from said second terminal to said anode and the others each connected from said second terminal to a different one of said cathodes, and second bias circuit means for establishing a bias voltage on said auxiliary electrode comprising a second voltage reference device connected between said anode supply terminal and a third terminal to establish a voltage thereon lower than the voltage on said second terminal, and circuit means connecting said auxiliary electrode to said third terminal.

3. A character display circuit as in claim 2 further including a cathode reference terminal, a plurality of current-limiting impedance devices, one connected from said cathode reference terminal to each of said cathode drivers, and a further impedance device connected between said cathode reference terminal and said third terminal.

4. A character display circuit comprising an envelope containing an ionizable gas, an anode and a plurality of cathodes within said envelope, each of said cathodes having the shape of a segment of a character to be displayed, circuit means for establishing a glow potential between said anode and different combinations of said cathodes for causing said different combinations of cathodes to glow and thereby display different characters, said circuit means including a plurality of cathode drivers, one connected to each of said cathodes, and means for selectively energizing said cathode drivers to render different combinations of their connected cathodes glowing, an auxiliary electrode in contact with the ionizable gas and in operative relation with said anode and cathodes, bias circuit means for said anode and cathodes including a first terminal at a predetermined voltage, an impedance connected from said first terminal to said anode, and a plurality of additional impedances each connected from said first terminal to a different one of said cathodes, and second bias circuit means for said auxiliary electrode including a voltage reference device connected electrically from said first terminal to a second terminal, and circuit means connecting said auxiliary electrode to said second terminal.

5. A character display circuit as in claim 4 further including an anode supply voltage terminal, with circuit means connected between said terminal and said anode, and a second voltage reference device connected from said anode supply voltage terminal to said first terminal.

6. A character display circuit for displaying any one of a plurality of characters in each of a plurality of side-by-side character positions, comprising a plurality of anodes, one in each of said character positions, a plurality of groups of cathodes, each such group being associated with one of said anodes at one of said character positions, each of the cathodes having the shape of a segment of one of the characters to be displayed, each of said anodes and its associated cathodes being disposed in an ionizable gas atmosphere capable of sustaining cathode glow discharge, a plurality of cathode conductors each electrically connected to one of the cathodes in each character position, a plurality of cathode drivers, each connected to one of said cathode conductors, for energizing said cathodes selectively in response to a first set of input signals, anode selection circuit means for selectively energizing said anodes, in synchronism with the selective energization of said cathodes, in response to a second set of input signals, for displaying selected characters in each of said character positions, an auxiliary electrode in the gaseous atmosphere associated with each character position, the current therethrough being a function of the number of cathodes which are glowing, an anode voltage supply terminal, with said anode selection circuit means connected between said terminal and each of said anodes, anode bias circuit means including a second terminal, first voltage reference means including a voltage reference device connected from said anode supply voltage to said second terminal, and a plurality of impedance devices, each connected from said second terminal to one of said anodes, and an auxiliary bias circuit means including a second voltage reference means connected from said anode supply voltage terminal to a third terminal and circuit means connecting said auxiliary electrodE to said third terminal,

9. A character display circuit for displaying any one of a plurality of characters in each of a plurality of side-by-side character positions, comprising a plurality of anodes, one in each of said character positions, a plurality of groups of cathodes, each group being associated with one of said anodes and being located in one of said character positions, each of the cathodes having the shape of a segment of one of the characters to be displayed, each of said anodes and its associated cathodes being disposed in an ionizable gas atmosphere capable of sustaining cathode glow discharge, a plurality of cathode conductors each electrically connected to one of the cathodes in each character position, a plurality of cathode drivers, each connected to one of said cathode conductors, for energizing said cathodes selectively in responseo to a first set of input signals, anode selection circuit means for selectively eeergizing said anodes, in synchronism with the selective energization of said cathodes, in response to a second set of input signals, for displaying selected characters in each of said character positions, an auxiliary electrode in the gaseous atmosphere associated with each character position, anode bias circuit means including a first terminal at a predetermined potential and a plurality of impedance devices each connected from said terminal to one of said anodes, and an auxiliary electrode bias circuit including a voltage reference device connected electrically from said first terminal to said auxiliary electrode.

11. A character display circuit as in claim 9 further comprising an anode supply voltage terminal, with said anode selection circuit means electrically connecting said terminal to each of said anodes, and a voltage reference device electrically connected from said anode supply voltage terminal to said first terminal.

12. A character display circuit for displaying any one of a plurality of characters in a plurality of side-by-side character positions, comprising an envelope formed of a front plate with a viewing window and a rear plate, said plates being sealed together along a predetermined perimeter surrounding the side-by-side character positions to establish a gas tight enclosure, an ionizable gas within said enclosure at a pressure capable of sustaining a cathode glow discharge, a plurality of anodes, one at each of said character positions within said envelope, a plurality of groups of cathodes, each such group being associated with one of said anodes and being located in one of said character positions, each of the cathodes having the shape of a segment of one of the characters to be displayed, a plurality of elongated conductors extending within said envelope, each electrically connected to one of the cathodes in each character position, and each connected electrically to a terminal outside said envelope for connection to an external circuit, insulating material separating each of said conductors from all of the cathodes except the cathode in each character position to which it is connected, anode selection means for energizing said anodes sequentially and cathode selection means for selectively energizing different combinations of said cathode conductors sequentially, in synchronism with sequential energization of thE anodes, to form a side-by-side character display along said character positions, an auxiliary electrode associated with each of said character positions and being in operative relation with the anode and the cathodes in each such position, anode bias circuit means including a first terminal at a predetermined potential and a plurality of impedance means each connected electrically from said first terminal to a different one of said anodes, cathode bias circuit means including a further plurality of impedance means each connected electrically from said first terminal to a different one of said cathodes, and a voltage reference device connected electrically from said first terminal to said auxiliary electrode.

13. A character display circuit as in claim 12 wherein the auxiliary electrode has a portion thereof located between the anode and cathodes in each character position and those of the next adjacent character position, further including an anode voltage supply terminal connected through said anode selection circuit to each of said anodes and a further reference voltage device connected from said anode voltage supply terminal to bias the auxiliary electrode to a predetermined voltage below said anode supply voltage for isolating the anode and cathodes of each character position from those of all of the other character positions.

14. A system for operating multiple-position display devices having a plurality of groups of cathode elements situated in an ionizable medium, an anode associated with each of the groups, and an auxiliary electrode that is common to all of the groups and shields them from each other, comprising means coupled to each of the cathode elements for driving them selectively in response to a first set of input signals, means coupled to each of the anodes for energizing them selectively in response to a second set of input signals, voltage supply terminals connected to the cathode driving means and to the anode energizing means for receiving operating potential for them, voltage reference means coupled between the auxiliary electrode and the voltage supply terminal of the anode energizing means, and impedance means coupled between the voltage reference means and the cathode driver voltage supply terminal.

15. The display system of claim 14 further comprising resistance means also coupling each of the cathode elements and each of the anodes to said voltage reference means.

16. The display system of claim 15 wherein the voltage reference means comprises a pair of voltage reference devices connected in electrical series with said impedance means, and said resistance means couples the anodes and cathode elements to the junction of the voltage reference devices.

18. The display system of claim 17 wherein the anode energizing means comprises a voltage switch for each anode, and the anodes and cathode elements are each coupled to said voltage reference means for being pre-biased.

19. The display system of claim 18 in which the cathode drivers are connected to a source of information signals to control the pattern to be displayed and the anode drivers are connected to a source of position control signals to select the position for each display pattern in the deivce.

20. The display system of claim 18 wherein the anode drivers are connected to a source of information signals to control the pattern to be displayed and the cathode drivers are connected to a source of position control signals to select the position for each display pattern in the device.