US3855500A

US3855500A - Gaseous glow-discharge indicator system

Info

Publication number: US3855500A
Application number: US00374133A
Authority: US
Inventors: Y Yanagisawa
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1970-09-01
Filing date: 1973-06-27
Publication date: 1974-12-17
Anticipated expiration: 1991-12-17

Abstract

A gaseous glow indicator tube in which there is contained a plurality of indicator units of a first type and additional indicator units of different types, the anodes and cathodes of all units lying in a common plane, the anodes being energized on a time sequential basis, corresponding cathode segments of each indicator unit being connected to a common energizing lead, whereby only those segments are caused to glow which have their associated anodes energized and which are energized through their respective cathode leads. The cathode segments of at least one of the additional indicator units having a smaller area than that of the cathode segments of the first type indicator unit. The additional type indicator units being particularly designed to indicated exponents, ''''overflow'''' and other functions being performed.

Description

Unite States Patet 11 1 Yanagisawa Dec. 17, 1974 [54] GASEOUS GLOW-DISCHARGE INDICATOR 3,435,270 3/1969 Vodicka 313/1095 3,573,532 4/1971 Boucher 3l3/109.5 SYSTEM 3,588,571 6/1971 Vemura et 211.... 313/1095 n t Yuzuru Yanagisawa, Fujisawa, 3,641,383 2/1972 Tagawa 313/1095 Japan 3,641,390 2/1972 Nakamura 315/169 R 3,679,933 71972 N'kd t'l .315169RX [73] Asslgnee: Sony Corporation, Tokyo, Japan I d a a e d l [22] Filed: June 27, 1973 Primary ExaminerPalmer C. Demeo Attorney, Agent, or Firm-Hill, Gross, Simpson, Van [21] Appl' 374l33 Santen, Steadman, Chiara & Simpson Related US. Application Data [63] Continuation of Ser. No. 172,855, Aug. 18, 1971, [57] ABSTRACT v abandoned A gaseous glow indicator tube in which there is contained a plurality of indicator units of a first type and [30] Forelgn Apphcatmn Pnonty Data additional indicator units of different types, the an- Sept. 1,1970 Japan 45-87014 odes and cathodes of all units lying in a common Apr, 26, 1971 Japan 46-27396 plane, the anodes being energized on a time sequential basis, corresponding cathode segments of each indica- 52] us. c1 315/169 TV, 313/517 tor unit being connected to a common energizing lead, [51 Int. Cl 1101 61/66, HOSb 41/38 whereby only those segments are Caused to glow [58] Field 01' Search 313/1095, 210, 220; which have their associated anodes energized and 315/169 R, 169 T 58 which are energized through their respective cathode leads. The cathode segments of at least one of the ad- [56] References Cmd ditional indicator units having a smaller area than that UNITED STATES PATENTS of the cathode segments of the first type indicator 2,735,038 2/1956 Hancock 313/1095 x unit- The additional yp indicator units being P 3,187,320 6/1965 Kupsky 313/1095 UX larly designed to indicated exponents, overflow and 3,231,776 1/1966 Britnell et ul. 313/1095 other functions being performed. 3,289,198 11/1966 Dickson, Jr. et a1 313/1095 UX 3,327,154 6/1967 Bowerman 313 1095 9 Claims, 5 Drflwmg Figures fzea PATEN'i'ED 0E0 i "x mm :1 855 500 SHEET 10F 2 55 Z: J J 50 w; m w Mm /0 1 ii ri 05$ /3 /6 g g m M J x /2 C/ILCULA701Q MA [IQ/ I N VEN TOR 702 we a xv/ma/smm BY ATTORNEYS GASEOUS GLOW-DISCHARGE INDICATOR SYSTEM This is a continuation, of application Ser. No. 172,855, filed Aug. 18, 1971, and now abandoned.

CROSS REFERENCE TO RELATED APPLICATIONS The present invention is an improvement over the invention disclosed in pending application, Ser. No. 128,888, filed Mar. 29, 1971, and it is also an improvement over the invention disclosed in Ser. No. 155,555, filed June 22, 197], now U.S. Pat. No. 3,728,571, both of which are assigned to the same assignee as the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to gaseous glow indicator tubes and particularly to that type of indicator tube in which a number of indicator units are contained within a sealed envelope and which have one or more anodes for each indicator unit and a number of cathodes for each indicator unit, the anodes being energized on a time sequential basis, and the cathodes being connected to a potential source which is negative with respect to the anode potential source.

2. Description of the Prior Art Gaseous glow indicator tubes which include a plurality of indicator units mounted inside a transparent envelope and which are utilized for displaying numerals, symbols, letters, or the like, have been commercially available. For example, such indicators have been used with electronic counters and various other indicating means. One example of such indicators are the socalled "Nixie" tubes in which an anode electrode and a plurality of cathode electrodes are aligned in a stack one above the other such that selected cathode elements may be energized so that an observer sees a selected numeral or letter. Other glow indicator tubes utilize cathode segments mounted in a common plane with an anode in the form of a wire screen or mesh mounted in a second plane and which when various cathode segments are energized at the same time that the corresponding anode is energized the unit will glow.

Such prior art indicator tubes utilized a separate lead for each of the anodes, or alternatively provide separate leads for each of the cathode segments. This resulted in indicator tubes with a very large number of leads and limited the minimum size of the unit as well as requiring many electrical connections to be made to each of the units.

In U.S. Pat. No. 3,588,571 an indicator tube is described in which each of the cathode electrodes or a plurality of indicating units are commonly connected to each other by a single lead. This eliminates the necessity for a number of cathode leads corresponding to the number of cathodes in the entire indicator tube.

SUMMARY OF THE INVENTION In the tubes above referred to, no means was provided to indicate an over-flow or to indicate other operational functions which should be brought to the attention of the operator.

The present invention comprises a gaseous glow indicator tube having a number of indicator units in which the cathode and anode elements are formed in a common plane and wherein the associated cathode segments of each of the indicating units are electrically connected together and are simultaneously energized and in which the anode segments for separate indicating units are time sequentially energized such that a particular indicating unit which has its anode energized produces an indication. Such a tube of this invention has at least one additional indicating unit in which the cathode and anode elements are formed in a common plane, and each of the cathode elements has a smaller area than that of each of the cathode elements of the indicating units.

Accordingly, one of the objects of this invention is to provide an improved gaseous glow indicator tube in which there is a plurality of indicator units, an additional plurality of indicator units of different types, at least some of said additional indicator units providing an indication of a function being carried out by the apparatus with which the indicator tube is associated.

Another object of the present invention is to provide a novel gaseous glow indicator tube in which a plurality of indicating units and at least one additional'unit are accommodated therein.

Still another object of the present invention is to provide a gaseous glow indicator tube in which there is contained a plurality of indicator units of a first type and at least one indicator unit of a different type, the additional indicator unit having an indicating area which is smaller than the indicating area of each of the first type indicator units, whereby the glow from the additional indicator unit is brighter than the glow from the first type indicator units.

A further object of this invention is to provide a gaseous glow indicator tube in which a plurality of indicat BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plane view of an assembled gaseous glow indicator tube embodying the novel features of the present invention, the center section of which has been broken away;

FIG. 2 is a sectional view of the gaseous glow indicator tube of FIG. 1 showing only the supporting base, the enclosing envelope, the insulating layer and an indicating unit;

FIG. 3 is a schematic wiring diagram of the gaseous glow indicator tube of this invention illustrating the electrical connections between the cathode elements and anode elements of two of the indicator units and illustrating the cathode and anode elements of a functioning indicator unit;

FIG. 4 is a diagrammatic view of a modified form of indicator tube which, in addition to displaying a number of digits, also is able to display a times sign, exponents and also functional operation;

FIG. 5 is a schematic wiring diagram of the gaseous glow indicator tube shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 diagrammatically illustrates a gaseous glow indicator tube 10. This indicator tube 10, as shown in FIG. 2, includes a plate or base 1 1 formed of insulating material such, for example, as glass. Disposed on the base 11 is a strip of insulating material 13, on which in turn are formed the indicating units 16, including both the cathodes and the anodes, as hereinafter will be explained. The insulating layer 13, as well as the indicating units 16 are enclosed by a transparent glass cover 12 which is sealed to the base 11. The chamber enclosed by the glass cover 12 is filled with a suitable ionizing gas.

Referring back to FIG. 1, the indicating units 16 are made up of a large number of indicia diagrammatically shown as 16a, 16b, 16p.

As presently will be explained, each indicating unit 16 is made up of a plurality of anodes and a plurality of cathode segments and provides an indication. It is, of course, necessary to apply a potential between a cathode segment and its associated anode, it being understood that the cathode will be negative with respect to the anode. To accomplish this, leads must come out from the indicator tube envelope 12, and such leads are shown as leads 17 to 37 in FIG. 1.

As will be more fully appreciated by referring to FIG. 3, each of the indicator units 16a to 16p is formed of eight cathode segments that are insulated from each other and two anode segments. In the present invention all of the corresponding cathode segments are electrically connected together. The individual indicator units have a pair of anode elements which are electrically connected together and which are independently energized so that at a particular time on the particular indicator unit which has its pair of anode elements energized, will glow. Thus, even though the corresponding cathode segments of all of the indicator units 16a to 16p are energized, only the particular indicator unit which has its anodes energized will glow. The cathode segments and anode segments are formed in a common plane parallel with the plane of the layer 13 on which they are formed. Another advantage of the present invention lies in the fact that all of the anode and cathode units lie in a common plane allow a glow tube to be constructed that is very thin and compact.

As shown in FIG. 3, each of the indicator units 16a to 16p is formed of eight cathode segments designated by numerals, 46 to 53, respectively. The segments are arranged to form a figure 8 with the decimal segment 53 at the lower right hand corner. For example,

segments

46, 48 and 50 are above each other and horizontal as viewed in FIG. 3.

Segments

47, 49, 51 and 52 are generally vertical as viewed in FIG. 3.

Anode segments

54 and 55 are mounted, respectively. between

cathode segments

48, 49, 50 and 51, and

cathode segments

46, 47, 48 and 52. Eight cathode energizing leads 38 to 41 and 43 to 46 extend generally horizontally on the insulating plate 11 with the leads 38 to 41 mounted adjacent the upper edge of indicator units 16a to 16p and cathode leads 43 to 46 mounted adjacent the lower edge of the indicator units 16a to 16p. These may be formed by any well known printed circuit technique.

As shown in H6. 2, the insulating layer 13 is mounted on the glass plate 11, and the cathode and anode segments 46 to 55 are formed on layer 13. The fact that both layer 13 and plate 11 are of insulating material enables the electrical connections to be made to the cathode and anode segments without any portions being shorted out.

As shown in FIG. 3, cathode lead 38 is connected by conductors 64 to each cathode segment 51 of all of the indicator units. At the crossing points of leads 64 with

leads

39, 40 and 41, the insulating layer 13 provides separation and insulation. Thus, the leads 64 may be placed on one side of the insulation layer 13 and openings are formed in the insulation layer 13 and connections are made to the respective segments through such openings.

Leads 63 connect lead 39 to each of the cathode segments 52 of the indicator units. Leads 61 connect each of the cathode segments 46 to the conductor 40. Leads 62 connect each of the cathode segments 48 to lead 41.

Leads 69 connect cathode segments 53 to lead 43. Leads 68 connect each of the cathode segments 49 to the lead 44. Leads 66 connect each of the cathode segments 50 to the lead 46. Leads 67 connect each of the cathode segments 47 to lead 45.

Lead 71 connects the two

anode segments

54 and 55 of the first indicator unit 16a to the movable contact of switch Sa.

Lead 76 connects the two anode segments 54' and 55 of the second indicator unit 16b to the movable contact of a switch Sb.

Each of the

anode segments

54 and 55 for a particular indicator unit are electrically connected together, but the anode segments for different indicator units are connected to a different switch Sa to Sp through leads 71, 76, etc., as shown in FIG. 3.

A battery E exemplifies a source of potential and has its negative terminal connected to ground and its positive terminal connected to the other terminals of the switches Sa to Sp for selectively applying a positive potential to the anode segment of the indicator units, the positive potential being sufficient to cause the adjacent activated cathode segments to glow.

The cathode leads 38 to 41 and 43 to 46 are connected to a calculator matrix 72 as shown in FIG. 3.

A plurality of push buttons 73 are mounted on the calculator matrix 72 and may be depressed for indicating a numeral between 0-9. For example, if the numeral 7 is selected, the cathode segments 46, 47 and 49 of all the indicator units 16a to 16p will be simultaneously energized but only the particular indicator unit which has its

anode segments

54 and 55 energized by the closing of one of the switches Sa to Sp will produce the number 7. Thus, for example, if switch Sb is closed thus applying a positive voltage to the anode segments 54' and 55 of unit 16b from the battery E, simultaneously when the cathode segments 46' and 47' and 49' are connected to a potential negative with respect to the anode potential from the calculator matrix 72, the indicator unit 16b will glow and the numeral 7 will be visible.

It is to be realized. of course, that the indicator units are energized on a time-sharing basis and the switches S0 to Sp may form a portion of the calculator matrix 72 and be selectively closed in synchronism with energization of the cathode segments such that the indicator 10 produces the desired indication. Techniques for connecting suitable energizing voltages in a time-sharing manner are known by those skilled in the art.

The indicator tube 10 of this invention, further provides an additional indicating unit (FIG. 3) on the insulating layer 13 to indicate a functional sign for the indicating units 16a to 16p. As shown in FIG. 3, the additional indicating unit 80 comprises five cathode segments 81 to 85 and six anode segments 86 to 91. The cathode segment 81 is connected to the lead 40 by a lead 92, the cathode segment 82 is connected to the lead 38 by a lead 93, the cathode segment 83 is connected to the lead 41 by a lead 94, the cathode segment 84 is connected to the lead 45 by a lead 95 and the cathode segment 85 is connected to the lead 44 by a lead 96. The anode segments 86 to 91 are commonly connected with each other by a lead 97 and this lead 97 is connected to a switch S which is connected to the battery E.

As clearly shown in FIG. 3, the indicating area of the cathode segment of each indicating unit 16a to 16p is designed substantially the same, however, the indicating area of the cathode segments of the additional indicating unit 80 is designed to be smaller in area than that of the cathode segments of the other indicating units.

According to this embodiment, the same voltage should be supplied to the cathode segments of the additional indicating unit 80 and the cathode segments of the indicating units 16a to 16p, however, the electric current density in the cathode segment of the additional indicating unit 80 is greater than that of the cathode segments of each of the other indicating units 16a to 16p because the indicating area of the additional indicating unit 80 is smaller than that of the indicating units 16a to 16p. 80 that the brightness of the additional indicating unit 80 is greater than that of the indicating units 16a to 16p, it has been found by way of example, that when the electric current density in the cathode segment 81 of the additional indicating unit 80 was selected to be 1.2 mA/mm its brightness was 300 foot-lamberts. In the same tube, the electric current density in the cathode segment 46 of the indicating unit 16a was 600 mA/mm its brightness was 150 footlamberts.

As described above, the calculated information in the output circuits of the matrix 72 is displayed on all of or a part of the indicating units 160 to 16p in the tube 10. If the results calculated in the matrix 72 require more digits than available such, for example, 20 digits, it is impossible to display all of the digits at one time on the indicating units 16a to 16p. That is, the tube as illustrated, is only able to display 16 digits, and four other digits are not displayed thereon. Under this set of circumstances, the predetermined required voltage supplied between the anode and cathode segments of the additional indicating unit 80 by the closing of its switch S,,, so that the additional unit 80 will be energized. As is well-known, the additional indicating unit 80 performs the so-called over-flow indication. The overflow indication is, as described above, brighter than the other indications. An operator is thereby notified that the display indication is an over-flow.

Further, all of the cathode segments 81 to 85 of the additional indicating unit 80 may be energized to indicate an over-flow. It is possible, however, to energize

only segments

82, 83 and 85, or 81, 82, 84 and 85, etc.

Further, it is possible to display a minus indication on the additional indicating unit 80. In order to display this minus indication, the cathode segment 83 alone is energized. This minus indication is brighter than the other indicating units, so that the operator is notified of such mark.

FIG. 4 illustrates the face of a second embodiment of the present invention. In this embodiment, there are a plurality of standard indicating units 101a to 101g, an indicating unit 103 for a multiplication mark, a indicating unit 104 for an over-flow or minus mark, indicator units 105a to 105C for exponent numerals representing the power to which the base 10 is to be raised, and an indicating unit 106 for a minus sign to be used in front of the exponent numerals 105a, 105b and 105( if it is to be the inverse power of the base 10. The above indicating units are all formed on a base of a tube 100. The indicating area of each cathode segment of the units 104, a to 1050 and 106 is smaller than that of the cathode segments of the other indicating units 101a to 1013, 102 and 103. As used herein, the units 104, 105a to 105C and 106 are termed additional indicating units, so that it will be understood that said brightness of the units 104, 105a to 1050 and 106 are greater than that of the other units.

FIG. 5 shows a fragmentary schematic circuit diagram of some of the indicating units illustrated in FIG. 4. The indicating unit 101a consists of seven cathode segments 111a to 117a having a conventional figure 8 formation. Additionally, there is a cathode segment 118a for a decimal point. Also, there is an anode segment 119a associated with the cathode segments 111a to 118a. Similarly, the indicating unit 1011) consists of seven cathode segments lllb to 1l7b formed as a figure 8, a cathode segment 118b for a decimal point and an anode segment 11% associated with the cathode segments lllb to 118b. Further, the exponent indicating unit 105a consists of seven cathode segments 12111 to 1270, in a figure 8 configuration, a cathode segment 128a for a decimal point and an anode segment 129a associated with the cathode segments 121a to 128a. The exponent indicating unit l05b consists of seven cathode segments 12112 to 127b, forming a figure 8, a cathode segment 128b and an anode segment 12% corresponding to all i of the cathode segments 121a to 128b.

In FIG. 5, each of the anode segments 119a to 12% of units 101a to l05b are connected to a source E through switches 131a to l4l b and a common lead 150. The corresponding cathode segments, for example, a, 115b, a and l25b of each unit are connected to each other by a common lead 151, and also the corresponding cathode segments 116a to l26b of each unit are connected to each other by a common lead 152. The leads I51 and 152 are grounded through resistances 151R and 152R and switches 1515 and 152s, respectively. Further, it will be understood that the connection of the other anode and cathode segments of the other units are arranged in the same manner. The switches of anode segments and cathode segments are controlled by a calculator matrix 72' t cause desired indications.

According to this second embodiment, it is possible to indicate a number composed of a number of digits multiplied by the base 10 raised to a power represented by an exponent composed of at least one digit such, for example, as 3.0621 X 10". For displaying said 3.0621 X 10", the standard indicating units 1010 to 103 are energized to indicate 3.0621 X 10, and indicating units 105b and 1050 are energized to indicate the exponent 12. In this case, the indicating areas of the cathode segments of the units lb and 1050 have been designed smaller than that of cathode segments of the units 101C to I03, and hence the brightness of the exponents is greater. The operators attention is thus directly called to the exponents. If an over-flow is contained, it may be displayed on the unit 104.

As shown in FIG. 5, a resistance 124R is connected between the cathode segment 125a and the common lead 151. Similarly, a resistance 126R is connected between the cathode segment 126a and common lead 152. Other resistances are connected between each cathode segment of each additional indicating unit and the corresponding common leads. Such resistances are formed on the base 100 when the indicating units are formed. As described above, the indicating area of each additional indicating unit is very small, so that the current density is great, and hence the life of the additional indicating units would be shorter than that of the indicating units. However, by adding the resistance, the life of the additional indicator unit may be extended. Of course, the value of the resistance should be selected so that the brightness of the additional indicating unit is greater than that of the other units. These resistance elements may be omitted if full brightness is desired.

Although the invention has been described in connection with the preferred embodiments, it is not to be so limited as changes and modifications may be made which are within the full intended scope of the invention as defined by the appended claims.

I claim as my invention:

1. A gaseous glow indicator tube comprising a base plate of insulating material, a transparent cap sealed to said base plate and forming a gas tight chamber therewith, an ionizing gas in said chamber, a sheet of insulating material within said chamber and disposed on said base plate, a plurality of main similarly segmented indicator units within said chamber on the outer face of said sheet, each of said segmented units including a like number of cathode segments similarly located in a predetermined pattern in each indicator unit, at least one anode segment forming a part of each indicator unit and each located on said insulated sheet in the same plane as said cathode segments, a plurality of energizing leads on said insulating sheet corresponding in number to the maximum number of cathode segments in a single indicator unit, secondary leads on the underside of said insulating sheet connected respectively to said cathode energizing leads; means connecting said secondary leads to said cathode segments through said insulating sheet, at least one anode energizing lead for each indicator unit, a secondary lead for each indicator unit connecting the anodes of each indicator unit to an anode energizing lead respectively, a secondary indicator unit in said chamber including at least one cathode segment and one anode segment disposed on said insulating sheet, each cathode segment of said secondary indicator unit being smaller in area than the area of any one of said cathode segments of said main indicator units, an energizing lead for each cathode segment of said secondary indicator unit located on said outer face of said insulating sheet, circuit connections between each of said cathode energizing leads of said secondary indicator unit and associated cathode segment, energizing leads for said anodes of said secondary indicator units connected to their associated anodes respectively, and means for connecting successively said anode energizing circuits to a positive source of potential on a time sharing basis and simultaneously connecting selected ones of said cathode segments of each indicator unit to the negative side of the same source of potential on the same time sharing basis, thereby to cause selected segments of each indicator unit to glow and in which there is provided a resistor element in each cathode segment energizing circuit of said secondary indicator unit, thereby to reduce the current density in each such cathode segment when energized, the resistive value of each resistance element being sufficient to reduce the glow of its associated cathode segment only to a point where the cathode segment is still brighter than the cathode segments of said main indicator units.

2. A gaseous glow indicator tube according to claim 1 in which the cathode segments of each indicator unit are arranged in a figure 8 pattern and in which the cathode segments of at least one secondary indicator unit are arranged in a pattern to display an overflow.

3. A gaseous glow indicator tube according to claim 1 in which the cathode segments of each indicator unit are arranged in a figure 8 pattern, and in which the cathode segments of at least one secondary indicator unit are arranged in a pattern to display an exponent of a number displayed by said main indicator units.

4. A gaseous glow indicator tube according to claim 1 in which the cathode segments of each indicator unit are arranged in a figure 8 pattern and in which the cathode segments of at least one secondary indicator unit are arranged in a pattern to display an overflow and other of said secondary indicator units are arranged in a pattern to display an exponent ofa number displayed by said main indicator units.

5. A gaseous glow indicator tube according to claim 1, in which at least some of said anode segments are U- shape with only a single such anode segment for each indicator unit in which it is located.

6. A gaseous glow indicator tube according to claim 1, in which at least one secondary indicator unit has five cathode segments arranged in a figure X configuration with four of such segments and having a cross bar between and spaced from the inner ends of the legs of the X.

7. A gaseous glow indicator tube according to claim 1, in which at least one secondary indicator unit has five cathode segments arranged in a figure X" configuration with four of such segments and having a cross bar between and spaced from the inner ends of the legs of the X", and in which six anode segments are positioned around the cathode segments and in the same plane.

8. A gaseous glow indicator tube according to claim 1 in which each indicator unit is formed on an insulating layer covered by a transparent cover, and each resistive element is formed on said insulating layer.

9. A gaseous glow indicator tube comprising a plurality of indicator units of one type each of which includes at least one anode and a plurality of cathode segments arranged in a figure 8 configuration, said anode and said cathode segments all lying in a common plane, at least one additional second type indicator unit each including at least one anode and a plurality of cathode segments arranged in a figure 8 configuration and positioned to represent a power of a number displayed by cathode segments of said one type indicator unit, each cathode segment of said second type indicator unit being smaller in area than the area of any one of the cathode segments of said one type indicator unit. a

tor units of said third type, and in which there is provided a resistor element in each cathode segment energizing circuit of said second type indicator unit, thereby to reduce the current density in each such cathode segment when energized, the resistive value of each resistance element being sufficient to reduce the glow of its associated cathode segment only to a point where the cathode segment is still brighter than the cathode segments of said one type indicator unit.

Claims

3. A gaseous glow indicator tube according to claim 1 in which the cathode segments of each indicator unit are arranged in a figure ''''8'''' pattern, and in which the cathode segments of at least one secondary indicator unit are arranged in a pattern to display an exponent of a number displayed by said main indicator units.

4. A gaseous glow indicator tube according to claim 1 in which the cathode segments of each indicator unit are arranged in a figure 8 pattern and in which the cathode segments of at least one secondary indicator unit are arranged in a pattern to display an overflow and other of said secondary indicator units are arranged in a pattern to display an exponent of a number displayed by said main indicator units.

5. A gaseous glow indicator tube according to claim 1, in which at least some of said anode segments are U-shape with only a single such anode segment for each indicator unit in which it Is located.

7. A gaseous glow indicator tube according to claim 1, in which at least one secondary indicator unit has five cathode segments arranged in a figure ''''X'''' configuration with four of such segments and having a cross bar between and spaced from the inner ends of the legs of the ''''X'''', and in which six anode segments are positioned around the cathode segments and in the same plane.

9. A gaseous glow indicator tube comprising a plurality of indicator units of one type each of which includes at least one anode and a plurality of cathode segments arranged in a figure 8 configuration, said anode and said cathode segments all lying in a common plane, at least one additional second type indicator unit each including at least one anode and a plurality of cathode segments arranged in a figure 8 configuration and positioned to represent a power of a number displayed by cathode segments of said one type indicator unit, each cathode segment of said second type indicator unit being smaller in area than the area of any one of the cathode segments of said one type indicator unit, a transparent envelope enclosing said indicator units and an ionizing gas in said envelope and means for selectively energizing said indicator units of said one type and said second type, further including an indicator unit of a third type which includes at least one anode and at least one cathode segment arranged to display a mathematical function, each cathode segment of said third type indicator unit being smaller in area than any one of the cathode segments of said first type indicator units and means for selectively energizing said indicator units of said third type, and in which there is provided a resistor element in each cathode segment energizing circuit of said second type indicator unit, thereby to reduce the current density in each such cathode segment when energized, the resistive value of each resistance element being sufficient to reduce the glow of its associated cathode segment only to a point where the cathode segment is still brighter than the cathode segments of said one type indicator unit.