US3679933A

US3679933A - Display system

Info

Publication number: US3679933A
Application number: US886812A
Authority: US
Inventors: Yasuo Nakada; Hideo Takita
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1968-12-23
Filing date: 1969-12-22
Publication date: 1972-07-25
Anticipated expiration: 1989-07-25
Also published as: NL146328B; GB1258949A; DE1963270A1; NL6918981A; DE1963270C2; JPS4810892B1

Abstract

A display system using a gaseous glow indicator tube having a plurality of indicator electrode units such as seven, for instance, each unit including a plurality of cathodes and having anodes disposed opposite the indicator electrodes. The indicator electrode units and the anodes are contained in an envelope and a driving circuit is provided for selectively feeding current to the indicator electrode units in such a manner that adjacent ones are not caused to glow successively.

Description

United States Patent Nakada et al.

[451 July 25,1972

[54] DISPLAY SYSTEM [72] inventors: Yasuo Nakada; Hideo Takita, both of Tokyo, Japan [73] Assignee: Sony Corporation, Tokyo, Japan [22] Filed: Dec. 22, 1969 [21] Appl. No.: 886,812

[30] Foreign Application Priority Data Dec. 23, 1968 Japan ..43/94737 [52] U.S.Cl ..3lS/l69 TV,313/109.5,315/169 R, 340/336 [51] Int. Cl. ..H05b 37/00 [58] Field ofSeai-ch ..3l3/109.5;315/169, 169 TV; 340/336 [56] References Cited UNITED STATES PATENTS 2,608,674 8/1952 Depp ..3l5/169 X 2,702,357 2/1955 Townsend ..3l5/l69X Primary ExaminerRoy Lake Assistant Examiner-Lawrence J. Dahl Attorney-Hill, Sherman, Meroni, Gross & Simpson [5 7] ABSTRACT A display system using a gaseous glow indicator tube having a plurality of indicator electrode units such as seven, for instance, each unit including a plurality of cathodes and having anodes disposed opposite the indicator electrodes. The indicator electrode units and the anodes are contained in an envelope and a driving circuit is provided for selectively feeding current to the indicator electrode units in such a manner that adjacent ones are not caused to glow successively.

8 Claims, 14 Drawing Figures PATENTEDJMS I972 3.679.933 sum 1 or 5 INVE/V TORS YASUO NAKADA HIDEO TAKI TA BM%AT TOR/VEYS mEminJm mn 3.673.933

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SHEEI 5 BF 6 INVENTORS YASUO NAKADA HIDEO TAKITA BY ATTORNEYS DISPLAY SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a display system for driving a gaseous glow indicator tube having a plurality of indicator electrode units mounted in the same envelope.

2. Description of the Prior Art There has been proposed a gaseous glow indicator tube comprising an envelope containing a plurality of indicator electrode units for providing a display of a number containing a plurality of figures. In the gaseous glow indicator tube, ionized plasma is produced by glow discharge in the envelope, and even after the discharge is stopped, ions are not destroyed and still remain in the vicinity of the discharged indicator electrode units. The presence of the residual ions leads to glow of neighboring electrode units, thus causing a wrong message display. This can be avoided by providing a partition between adjacent indicator electrode units to prevent the influence of the residual ions upon the neighboring electrode units, but this introduces difficulty in the fabrication of indicator tubes.

SUMMARY OF THE INVENTION Based upon the fact that the residual ions do not move very far before they are destroyed, in the present invention the indicator electrode units are caused to discharge not sequentially but, for example, alternately so as to avoid successive discharge of adjacent electrode units and hence prevent accidental discharge due to the presence of residual ions.

Accordingly, one object of this invention is to provide a display system for gaseous glow indicator tubes which are free from accidental discharge of the indicator electrode units.

Another object of this invention is to provide a display system for gaseous glow indicator tubes of the type having a plurality of indicator electrode units mounted in the same envelope which employs a driving circuit for holding the anode potentials of undischarged ones of the indicator electrode units sufliciently low to prevent accidental discharge.

Still another object of this invention is to provide a display system for gaseous glow indicator tubes of the type having a plurality of indicator electrode units mounted in the same envelope which employs a driving circuit for holding the anode potentials of undischarged ones of the indicator electrode units sufficiently low to prevent accidental discharge and for maintaining the potentials of unused cathodes positive.

Other objects, features and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing one example of an indicator tube to which this invention is applicable;

FIG. 2 is a block diagram illustrating one example of an indicator tube of this invention;

FIGS. 3A-3E are waveform diagrams for explaining the operation of the indicator tube of FIG. 2;

FIG. 4 is a schematic showing one example of the principal part of this invention;

FIGS. 5A, 5B and 5C are schematics illustrating other examples of the principal part of this invention.

FIG. 6 is a schematic showing one example of an experimental device, for explaining the operation of the principal part of this invention; and

FIGS. 7 and 8 are graphs, for explaining the operation of the device depicted in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 there is illustrated one example of a known indicator tube M for displaying a number containing a plurality of figures. Reference numeral 1 indicates a planar glass envelope in which an insulator base plate 2 having mounted thereon a plurality of aligned indicator electrode units A, B, C, D, is

placed and sealed with an ionizable gas suitable for supporting a glow discharge, as for example, argon or neon. The indicator tube M is caused to sequentially display the figures not concurrently but in a time-divisional manner so as to simplify the circuit construction and reduce power consumption of the indicator tube M. In this case the indicator electrode units A, B, C, D, are identical in construction with another.

The indicator electrode unit A, for example, comprises an anode a and a plurality of cathodes Ka Kb Kc Kg, arranged in the form of a number 8 on the base plate 2 in a predetermined spaced relation to the anode a,. The anodes a,, a a a ofthe indicator electrode units A, B, C, D, are respectively connected to an anode power source B+ through control switches Sa, Sb, Sc, Sn. Further, the cathodes Ka to Kn Ka to Kn Ka to Kn of the indicator electrode units A, B, C, D, are respectively connected together and are grounded through discharge ballast resistors Rk to Rk and selector switches Slt to Sk-,.

When the selector switches, for example, Sk Sk Sk Sk and Sk, are closed so as to display the number 2, those cathodes of each indicator electrode unit which correspond to the pattern 2 are grounded, and any of the control switches Sa, Sb, Sc, Sd, is closed to light the indicator electrode unit supplied with the anode voltage through the control switch selectively closed, thus providing a display of the number 2.

Under such conditions, if the control switches Sa, Sb, Sc, Sd, Sn are sequentially actuated, all the indicator electrode units sequentially display the number 2." Further, it is possible to cause the indicator electrode units A, B, C, D, to display a number containing a plurality of different figures in a time-divisional manner by altering the selected condition of the selector switches Sk to Sk in such a manner that the indicator electrode unit, for example, B is caused to display the number 3, while the control switches Sa to Sn are changed over one after another, that is, during the intervals between the closings of the switches Sa and Sb, for example. In the event the indicator electrode unit A displays the number 2 and then the unit B displays the number 3, there occurs the so-called crosstalk phenomenon such that the number 2 displayed by the unit A is lightly superimposed with the number 3 displayed by the unit B.

To avoid this, there has been proposed that partition walls be provided between adjacent indicator electrode units. However, providing partitions introduces difficulty in the placement of the insulator base plate 2 with the cathodes mounted thereon into the envelope 1.

In view of the foregoing, this invention provides a driving circuit for the indicator tube which avoids the crosstalk phenomenon without requiring partition walls.

In accordance with the present invention the indicator electrode units A, B, C, D are caused to glow at least alternately in a time-divisional manner. In order to light every other indicator electrode unit, the display system of the indicator tube may be constructed as shown in FIG. 2, which illustrates one example of this invention as applied to the display device of an electronic computer.

Reference numeral 3 indicates a shift register for memorizing a display output of the computer, the output of the shift resistor 3 being supplied to a buffer 4 through a gate circuit G. The output of the buffer 4 is fed to a decoder 5 for converting a binary digit into a code for display, and the selector switches Sk to Sk, connected to the cathodes of the indicator tube M are selectively actuated by the output of the decoder 5 to select those cathodes corresponding to a number defined by the operated output of the shift register 3.

The gate circuit G is supplied with a switching signal to be switchingly controlled, for example, at four-bit time intervals in the shift register 3. To perform this, a timing pulse generator 6 produces a timing pulse P at four-bit time intervals such as shown in FIG. 3A. The output pulse of the timing pulse generator 6 is applied to a flip-flop circuit 7, and its switching output P, (such as depicted in FIG. 3B) is, in turn, supplied to the gate circuit G, thereby permitting the application of the output of the shift register 3 to the bufier 4 at four-bit time intervals.

When a four-bit signal derived from the shift resistor 3 is fed to the buffer 4, the switching output P of the flip-flop circuit 7 is turned off to close the gate circuit G and hence to inhibit the application of the signal to the buffer 4 from the shift register 3 for a subsequent four-bit time period. Meanwhile, the signal of the preceding four-bit time period is stored in the buffer 4, and in the subsequent four-bit time period, the gate: circuit G is opened, the output of the shift resistor 3 is then supplied to the buffer 4. That is, an output of a shift pulse train of the shift register 3 is fed to the buffer 4 at four-bit time intervals to select the cathodes of the indicator tube M in accordance with the output of the buffer 4.

One portion of the output of the flip-flop circuit 7 is applied to a differentiation circuit 8 to derive at its output end a differentiated pulse P such as 3C. The resulting differentiated pulse P is fed to a rectifier circuit 9, at the output end of which is obtained pulse P of one polarity derived from the differentiated pulse P The pulse P is supplied to a shift register 10.

In the event that the indicator tube M has indicator electrode units of IO figures, the shift register 10 is made up of a decimal shift register from output terminals e, to e of which are sequentially derived shift pulses Pe, to Pe each having a pulse width of eight-bit time t, as shown in FIG. 3E. The shift pulses Pe, to Fe, derived at the output terminals 2, to e of the shift register 10 are respectively applied to odd-number driving signal input terminals f,, 3, f f, and f of 10 control switches Sa to Sj connected to the cathodes of the indicator tube M, while the shift pulses Pe to Pe derived at the output terminals a to 2, are respectively supplied to even-numbered driving signal input terminals f A, 3,, f and f,,, of the control switches Sa to Sj. Thus, the anodes of the indicator electrode units A to J of the indicator tube M are sequentially but alternately supplied with the anode voltage causing the indicator electrode units A to J to glow alternately in a time-divisional manner. Accordingly, the selector switches Sk, to SR, are selectively actuated in synchronism with the shift pulses derived from the shift resistor 3, thus providing a display of a predetermined number.

With such a display system, the indicator electrode units having just ceased to glow and those having started to glow are considerably apart from each other. Consequently, it is possible to alleviate the influence of the residual ions of the ionized plasma caused between the cathodes and anode of the indicator electrode unit previously lighted, thus avoiding the crosstalk phenomenon.

However, such a display system may still be defective in that the crosstalk phenomenon can occur when the anode voltage is increased to provide for increased glow intensity. It has been found that this defect can be removed by supplying the anodes of the indicator electrode units with a bias of lower potential than the anode voltage used to cause the units to glow and by applying a predetermined positive bias to those cathodes which are not selected in accordance with the operated output of the shift register 3. This will hereinbelow be described by way of example with reference to FIG. 4.

In the illustrated example control switches Sa to Sm for supplying an anode voltage to the anodes of the indicator tube M in a predetermined interlaced order are made up of transistors Q, to Q,,. Since the switching circuits Sa to Sm are all identical in construction, a description will be made in connection with the switching circuit Sa.

Reference character T indicates a transformer, in which input terminals f, of its primary winding are supplied with, for example, the shift pulse Pe, from the aforementioned binary shift register 10, and its secondary winding is connected at one end to the base of the transistor Q, and at the other end to the emitter of the transistor. The emitter is connected to the anode a, of the indicator tube M. The collector of the transistor Q, is connected to an anode power source B+ through a protective resistor R, of a relatively small resistance value, and a series voltage dividing circuit consisting of resistors R and R, is interposed between the anode power source 8+ and ground and is connected from the connection point of the resistors R and R to the emitter of the transistor Q,, that is, the anode a, of the indicator tube M through a resistor Ra of a high resistance value such as about I megohm.

With such an arrangement, when the positive shift pulse Fe, is applied to the input terminal f, from the output terminal e, of the shift register 10, the transistor Q, becomes conductive to bias the potential of the anode a, of the indicator tube M to that of the anode power source B+, causing the indicator electrode unit A to glow. In the event that no shift pulse Fe, is applied to the input terminal f,, the transistor Q, remains nonconductive and its emitter, that is, the anode a, of the indicator M, is supplied with a divided voltage from the voltage dividing circuit consisting of the resistors R, and R When the indicator electrode units A, B, C, are not caused to glow they are all supplied with the predetermined voltage from the voltage dividing circuit incorporated in each of the switching circuits Sa to Sm, that is, a voltage lower than that of the anode power source B+.

The cathodes of the indicator electrode units corresponding in position to one another are respectively interconnected, and the selector switches Sk, to Sk-, are interposed between the groups of the interconnected cathodes and ground. In the present example, the selector switching circuits Sk, to Sit,- are made up of transistors Q, to Q, in the same manner as the switching circuits Sa to Sm. Since the switching circuits Sk, to Sk, are identical in construction with one another, a description will be given of the switching circuit Sk,.

The emitter of the transistor Q, is grounded, and its collector is connected through a resistor Rk, to the common connection point of the interconnected cathodes Ka, to Kn, of the indicator electrode units. A series voltage dividing circuit consisting of resistors R and R is interposed between the anode power source 8+ and ground, and the voltage dividing point of the circuit is connected to the collector of the transistor (3,, that is, the common connection point of the cathodes Ka, to Kn,. Further, the base of the transistor 0, is connected to a bias power source E through a resistor R,,, if necessary.

Thus, when a selector pulse is applied from the decoder 5 to the base input terminal of the transistor 0,, the transistor 0, is made conductive to bias the cathodes Ka, to Kn, of the indicator electrode units A to N to ground potential. In the absence of the selector pulse, a positive bias is supplied to the cathodes Ka, to Kn, from the voltage dividing circuit made up of the resistors R and R Those cathodes of the indicator electrode units which are selected for displaying a desired number are biased to ground potential, while the other remaining cathodes are supplied with the positive bias voltage.

FIGS. 5A, 5B and 5C illustrate modified forms of the switching circuit incorporated in each anode circuit. In FIG. 5A the switching circuit consists of transistors Q,, Q and Q, of a relatively low reverse voltage, in which the input transistors Q, and Q are always held in the on state and the transistor 0,, is held in the ct? state. The anode of the indicator electrode unit is connected to the emitter of the transistor-Q and is normally supplied with a divided voltage based upon the voltage dividing ratio of the resistors R and K, through the base of the transistor 0,. When a negative control pulse is applied to the base of the input transistor 0,, the transistors Q, and Q are rendered non-conductive, so that the base potential of the transistor 0,, is biased to that of the anode power source B+ thereby biasing the anode to this potential. In the event that the reverse voltage V of the transistor Q, is higher than that of the anode power source 8+ in the present example, the resistors R, and R and the transistor Q: can be omitted, thus forming a simple circuit such as depicted in FIG. 5B.

In FIG. 5C the switching circuit consists of an input transistor Q,, a Zener diode connected in series to the collector of the transistor Q, and a transistor (1,. A voltage corresponding to the Zener voltage of the Zener diode D2 is normally applied through the base and emitter of the transistor Q to the anode of the indicator electrode unit connected thereto so as to stabilize the bias voltage which is normally impressed on the anode. The switching operation of the illustrated circuit is the same as that described in connection with FIG. 5A.

If the divided voltage of low potential supplied to the anodes of the indicator electrode units held inoperative is taken as Ea, Ea is selected to satisfy the following condition.

Ebb Ez Ea EZla-k) I (l) where Ebb is the voltage of the anode power source B+, Ez is a voltage for initiating a discharge between the anodes of adjacent indicator electrode units and Ea..- is a voltage for initiating a normal discharge between the anode a n t ho bie i di ator. lect ode unit- FIG. 6 is a circuit diagram showing one example of an experiment for obtaining the above condition. In this example, the indicator tube M is made up of two indicator electrode units A and B including anodes a and a and two pairs of cathodes Ka,, Ka and Kb Kb disposed opposite the anodes a and a and an anode a of an indicator electrode unit C. The cathodes are interconnected as previously described, and the aforementioned voltage Ebb is impressed between the anode a of the indicator electrode unit A and the cathode Ka disposed opposite thereto through a resistor Rk from an anode power source 8+ to cause a discharge between the anode a and the cathode Ka Further, a variable voltage is supplied from a variable intermediate output terminal of the anode power source B+ to the anode 0 of the indicator electrode unit B adjacent the unit A, by which a variable voltage is ap plied between the anode a of the unit C and the connection point of the interconnected cathodes Ka and Kb from an auxiliary anode power source Es.

The sealed gas, that is, an inert gas such, for example, as argon, neon or the like in the vicinity of the cathode Ka is ionized by the glow discharge between the anode a and the cathode Ka of the indicator electrode unit A to produce the so-called ionized plasma. Consequently, the cathode Ka adjacent to the cathode Ka, is excited to be ready for glow discharge by a relatively low electric field and hence is caused to glow by the electric field impressed between the anode a of the indicator electrode unit C and the cathode Ka In practice, when the indicator electrode unit C is caused to glow immediately subsequent to the completion of the glow of the unit A, the cathode K82 which should be held not to glow is caused to glow by the residual ions in the indicator electrode unit A.

With variations in voltage impressed on the anode a: of the indicator electrode unit B positioned midway between the indicator electrode units A and C, the discharge initiating voltage Ez causing the crosstalk phenomenon changes as indicated by curves h,, 11 h and hq in FIG. 7, in which the abscissa represents the variations in the discharge current between the anode a, and the cathode I(a of the indicator electrode unit A caused by changing the resistance value of the resistor RR, and the ordinate represents the voltage applied to the anode a of the indicator electrode unit C. The curves h,, h, h and h. respectively show the cases where the voltage, Ea, impressed on the anode a is 40V, 60V, 80V and 100V, and the oblique lines indicate the range of discharge of the anode a With a gradual increase in the voltage Ea impressed on the anode 0 the crosstalk discharge between the anodes a and 0 becomes more difficult to occur, so that the discharge initiating voltage Ez between the anode a and the cathode Ka can be increased.

However, when the voltage Ea increases to some extent, the ionization of the sealed inert gas is initiated between the anode a and the cathodes Kb and Kbg disposed opposite thereto and the crosstalk is likely to occur. Consequently, the voltage has an optimum value such that the crosstalk voltage Ez is maximum at a certain voltage as depicted in FIG. 8.

In the present example, where the anode power source voltage Ebb is l8OV, the discharge initiating voltage Ez between the anodes is 130V and the normal discharge initiating voltage E between the anode and the cathode of each indicator electrode unit is 130V, the crosstalk voltage Ez is maximum with the voltage Ea being approximately 100V.

Under these conditions the crosstalk phenomenon can be substantially inhibited.

In the region covered by the oblique lines in FIG. 8 wherein the bias voltage Ea impressed on the anodes a is smaller than the difference between the discharge initiating voltage Ez between the anodes of adjacent indicator electrode units and the anode power source voltage Ebb, the crosstalk generating voltage Ez cannot be measured. As has been described above, in the present example the indicator electrode units are alternately caused to glow and, in addition, the anodes of the indicator electrode units which are not caused to glow are supplied with the bias voltage Ea of lower potential than the normal discharge voltage of the indicator electrode units, thereby ensuring to avoid the crosstalk phenomenon.

Consequently, this arrangement prevents crosstalk between adjacent indicator electrode units and permits stable timedivisional display without requiring mechanical protective means such as partition walls between adjacent indicator electrode units. Further, this allows ease in the fabrication of the indicator tube.

With an increase in the bias voltage Ea supplied to the anodes of the indicator electrode units which are not caused to glow, the crosstalk phenomenon can be prevented with more ease, so that the bias voltage Ea can be increased, by supplying a positivebias voltage to cathodes which are not selected at that time. In other words, the application of a positive bias voltage to those cathodes causes an increase in their mean potential, so that even if the bias voltage Ea applied to the anodes opposing those cathodes is increased, it can be held within the range of the discharge initiating voltage Ez between the cathodes and the anodes, thereby further avoiding the crosstalk phenomenon.

Although the present invention has been described as being applied to an indicator tube in which a plurality of cathodes are provided in one plane, the invention is applicable to an indicator tube of the type employing a plurality of cathodes arranged one above another as in the Nixie Tube (Trademark of Sylvania We claim as our invention:

1. A display system comprising:

a gaseous glow multi-unit display indicator tube having an envelope;

a plurality of aligned indicator electrode units disposed within said envelope, each of said indicator electrode units having a plurality of cathodes and an anode respectively disposed generally opposite the cathodes of each unit;

means associated with each of said indicator electrode units for applying a voltage bias between its anode and selcted ones of its cathodes; and,

means for selecting and actuating the voltage applying means of different ones of said indicator electrode units successively in a time divisional manner such that two adjacent units are not actuated in adjacent time intervals.

2. A display system in accordance with claim I wherein the cathodes of each of the indicator electrode units are arranged in like geometric patterns 7 V V I 7 3. A display system as claimed in claim 2 which includes means for interconnecting corresponding cathodes of each of the indicator electrode units.

4. A display system as claimed in claim 2 wherein the cathodes are arranged substantially in a single plane.

5. A display system as claimed in claim 6 wherein a voltage divider is provided at each of said anodes and having means for being coupled to a power supply, said voltage divider normally applying only a portion of said power supply to said ,anodes, and switching means for causing said voltage divider to apply a larger voltage to said anodes when a signal is received from said drive means.

6. A display system comprising: a gaseous glow-unit indicator tube having an envelope;

units having a plurality of cathodes and an anode respectively disposed generally opposite the cathodes of each unit;

circuit means for supplying current from said anode to as sociated ones of said cathodes;

means for switchably coupling selected ones of said cathodes to said circuit means to cause a desired figure display from one of said indicator electrode units; and,

drive means for successively supplying a source of voltage to one of said anodes and to the other anodes on a time sequential basis and such that two adjacent anodes are not actuated in adjacent time intervals through said circuit means 7. A display system comprising:

a gaseous glow multi-unit indicator tube having an envelope;

circuit means for supplying current from said anode to associated ones of said cathodes;

means for switchably coupling certain ones of said cathodes to said circuit means to cause a desired figure display from one of said indicator electrode units; and,

drive means for successively supplying a source of energizing voltage to said anode on a time sequential basis and such that adjacent anodes are not energized in adjacent time intervals by said circuit means whereby adjacent indicator electrode units are prevented from developing a display successively.

8. A display system in accordance with claim 6 which includes means for applying a positive bias voltage to certain ones of said cathodes which are associated with anodes which are not biased by said drive means

Claims

1. A display system comprising: a gaseous glow multi-unit display indicator tube having an envelope; a plurality of aligned indicator electrode units disposed within said envelope, each of said indicator electrode units having a plurality of cathodes and an anode respectively disposed generally opposite the cathodes of each unit; means associated with each of said indicator electrode units for applying a voltage bias between its anode and selcted ones of its cathodes; and, means for selecting and actuating the voltage applying means of different ones of said indicator electrode units successively in a time divisional manner such that two adjacent units are not actuated in adjacent time intervals.

2. A display system in accordance with claim 1 wherein the cathodes of each of the indicator electrode units are arranged in like geometric patterns.

3. A display system as claimed in claim 2 which includes means for interconnecting corresponding cathodes of each of the indicator electrode units.

5. A display system as claimed in claim 6 wherein a voltage divider is provided at each of said anodes and having means for being coupled to a power supply, said voltage divider normally applying only a portion of said power supply to said anodes, and switching means for causing said voltage divider to apply a larger voltage to said anodes when a signal is received from said drive means.

6. A display system comprising: a gaseous glow-unit indicator tube having an envelope; a plurality of aligned indicator electrode units disposed within said envelope, each of said indicator electrode units having a plurality of cathodes and an anode respectively disposed generally opposite the cathodes of each unit; circuit means for supplying current from said anode to associated ones of said cathodes; means for switchably coupling selected ones of said cathodes to said circuit means to cause a desired figure display from one of said indicator electrode units; and, drive means for successively supplying a source of voltage to one of said anodes and to the other anodes on a time sequential basis and such that two adjacent anodes are not actuated in adjacent time intervals through said circuit means.

7. A display system comprising: a gaseous glow multi-unit indicator tube having an envelope; a plurality of aligned indicator electrode units disposed within said envelope, each of said indicator electrode units having a plurality of cathodes and an anode respectively disposed generally opposite the cathodes of each unit; circuit means for supplying current from said anode to associated ones of said cathodes; means for switchably coupling certain ones of said cathodes to said circuit means to cause a desired figure display from one of said indicator electrode units; and, drive means for successively supplying a source of energizing voltage to said anode on a time sequential basis and such that adjacent anodes are not energized in adjacent time intervals by said circuit means whereby adjacent indicator electrode units are prevented from developing a display successively.

8. A display system in accordance with claim 6 which includes means for applying a positive bias voltage to certain ones of said cathodes which are associated with anodes which are not biased by said drive means.