US2887610A - Electron discharge device - Google Patents

Description

3 Sheets-Sheet 1 y G. F. SMITH ELEKITRON DISCHARGE DEVICE May 19, 1959 I Filed Jan. 12, 1955 lllllk' v ,a 1 1. ni..

May 19, 1959 G. F. SMITH ELECTRON DISCHARGE DEVICE Filed- Jan. 12, 1955 :5 sheets-'sheet 2 I V24 Vzw V26 M I j 3 Sheets-Sheet 3 w/wwda/7i!! [5.44% 15:57 )fidi/,WIM

GfnsMn-H ELECTRON DISCHARGE DEVICE May 19, 1959 Filed Jan. 12, 1955 www @faire /S' .Lz/ffy,

United States Parent O ELECTRON DISCHARGE DEVICE George F. Smith, Los Angeles, Calif., assigner to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware This invention relates to electron tubes and moreparticularly to a secondary emission counter tube suitable for use in a digital computer.

Many types of counters used in digital computers are bulky and expensive. They generally require a considerable amount of power. This is particularly true of bi-stable multivibrators and other .digital type counters in which vacuum tubes are employed. Transistor multivibrators and other transistor counters are useful in reducing both the size of and power consumption of digital computers; howeverfan extremely large number of circuit connections must be made in order to construct computers in which either vacuum tubes or transistors are employed. Furthermore, the counting modulus of vacnum tube or transistor Adigital counters cannot be easily increased to, for example, decade counters which have numerous other practical applications. In such cases, the c ost of construction of computer is sizably increased not only by the number of circuit connections .but also bythe 'precision with which the circuit elements must be connected and by the number of circuit elements necessarily employed in these digital counters. When tranice are not intended as aldefinition of the limits of thejin-= vention.

Fig. l is a sectional view of one embodiment of 'the counter tube of theinvention shown with associated cir-l cuitry; l I` Fig. 2 is an equivalent circuit diagram of the tube of Fig. l with associated circuitry;

Figs. 3, 4, and 5 are graphs showing voltage-current curves characteristic of the operation of the embodiment of the invention illustrated in Fig. 2;

Fig. 6 is a plan view of another embodiment ofthey counter tube of the invention;

Fig. 7 is a broken-away section of the tube of Fig. 6;' Fig. 8 is an equivalent circuit diagram of the tube ot Figs. 6 and 7 shown with associated circuitry; and Fig. 9 s a graph of voltage-current curves characteristic of the operation of the counterl tube shown in Fig.y 8. Referring to Fig. l, a secondary emission counter tube l0 is shown having an evacuated envelope 12. The "counter tube 1G has a plurality of pin connectors 14 connected, respectively, to a pulse generator 16, a utilization. device 18, `a delay device 20, and an inverter amplifier .22. A resistive cylinder 24 is disposed inside of and coritiguous to the envelopev 12 of the counter tube 10. .The resistive cylinder 24 may consist of a material suchu'as stannous chloride which mayv be applied 'tothe envelope 12. According totechniques well known in the art, the resistivity of such a cylinder of stannous ,chloride maybev varied, over a wide range, and therefore can be used as a resistive layer or as a conductive layer. A, l' i yOn the internal surface of the resistive cylinder 24;

i four relatively short metallic cylinders 26, 28, 30and 32 sistors are employed, their relatively small size also increases the diiiiculty of making numerous accurate circuit connections.

It is therefore an object of the invention to provide a secondary emission counter tube having a simple mechanianodes is positioned within an evacuated envelope and a resistive element is provided between each pair of adjacent anodes. A wire grid is 'then disposed adjacent the anodes to act as a collector electrode and a single cathode is disposed within the envelope on the side of the collector electrode opposite the anodes to provide a source of electrons. Pulses are then impressed between the collector electrode and a point of reference potential to change the potential of each of the anodes from very near the potential of the cathode to very near the potential of the collector electrode or vice versa. the anodes are thus sequentially raised or lowered, whereby the tube may have a counting modulus equal to the number of anodes, e.g. ten in a decade counter which may be found to be of particular utility due to the decimal system of numbers which is widely used.

i The novel features lwhich are believed to be characteristic of the invention, both as to its organizationjand method of operation, together with further objects and advantages thereof, will be better understood from the .s

The potentials of for the purpose of illustration and description only, and

are shown. The cylinders 26, 28, 30, and 32 may readily be disposed on the internal surface of the resistivec'yli inder 24. This very fact contributes substantially tothe particular utility of the counter tube v10 because the cylinders 28 and 30 are secondary emissive and act as rst and second anodes respectively. yBy the usel of this type of construction internal and external yrnetal-to-nietal connectors may thus be avoided. The cylinders 26,128, 30, and 32 may vbe easily manufactured by brushing'fa liquidv suspension of silver or aluminum particles onto the resistive cylinder 24. The conductive cylinders 26; 28, 30, and 32 may also be conveniently evaporated onto the resistive cylinder 24 by masking offappropriate' areas of the resistive cylinder 2`4 and evaporatinga metalsuch as aluminum onto the internal surface of the resistive cylinder 24. i' 1 i Disposed Within the resistive cylinder 24 and spaced from the conductive cylinders 26, 28, 30, and 32 isa, helical metallic grid 34 which serves as a collect''felectrode. The collector 34 is positioned within envelope 12 by being attached to three axial pins 36, only one beinga pin connector, while the other two pins are not shown in Pig. 1. In the geometric center of the envelope 12, a cylindrical cathode 38 is shown having a cover 40 enclosing its right end. The cathode 38 is mechanically supported by means of three supporting pins 42, one being a pin connector as shown in Fig. 1, while the other two are not illustrated. Th cathode 38 is provided with coiled filament 44, one end of which is connected to apin connector 46, andthe other end of which is `connected to the enclosing cover 40 of cathode 38. i' The metallic cylinder 32 serves both as'a connector and as an anode. To this end, the enclosing cover 40v of cathode 38 is directly connected to the metallic cylinder 32 by lead 33. Likewise, the metallic cylinder `26 serves both as an anode and as a connector. The metallic cylinder 26 is accordingly connected to the collectorl 34 by means of a connection 48 tothe pin connector 36. The :first anode 28 and the second anode 30 are respec- F.. A ...1, a .c

tively connected to separate pin connectors 50 and 52 by leads 27 and 31. The axial pin connectors 46, 50, 42, 52, and 36 are maintained in appropriate alignment by meansof dielectric *cup` 54 which is disposed on the left. end of the envelope 12 whereby the axial pin connectors may projectthrough the cup.

The filament 44. is supplied with direct current by means of a filament source of potential 56, which is connected lbetween pin connectors 46 and 42 connected respectively to filament 44 and cathode 38. The cath ode 38 is connected. to ground through a resistor 58 which has a terminal connected to `the pin connector 42. The collector 34 is maintained at a potential positive with respect to thecathode 38 by means of a collector source of potential 60 which has ay positive `terminal connected to the pin connector 36 through a resistor 62.

p The pulse generator 16 is connected through a blocking capacitor .66 to the pin connector 36 to apply pulses to the collector 34 kwhichlarel positive with .respect to ground. With a voltage pulse indicated by 68, the coun tertube may be employed to count positively or negatively, i.e., the anodes 28 and 30 may be initially main- "esonero tained near the'` potential of the cathode 38. or near the 1 taining the' collector 34 ata constant direct-current potential and by pulsing the cathode 38 in a negative or posi tive direction, respectively. A reset mechanism is employed which comprisesr a delay device 20 and an inverter amplifier 22 which are seriallyconnected. between the anode through the pin 'connector 52 and the collecfor 34y throughV they pin connector 36. After a, second of' the pulses 68 is received or impressed upon the collector 34, the anode 30 will risc in potential, thereby impressing a pulse shown at 70 on the delay device 20 through the pin connector 52. The pulse is delayed by delay device 20, amplified and inverted by inverter amplier 22, which may be initially biased below cut-off, and impressed on the pin connector 36 as a negative pulse 7,1. The potential of both anodes 28 and 30 then may againV be reduced to the potential of cathode 38 by the negative pulse 71 impressed upon t-he collector 34.. Resetting may, also be accomplished by pulsing the cathode 38 in a positive direction rather than by `pulsing the collector 34 in a negative direction..

The utilization device 18 is connected to the pin connector 501m order to indicate the existing stable state of they anode 28. As will be more fully explained hereinafter the anode 30 does not indicate the number of counted pulses, but only serves to reset the` counter tube 10. The counter tube 10 thus has only two stable` states, i.e. when the anode 28 is negati-ve and when it is positive. Negative and positive in this context mean that the? anode 28 is at substantially the same potential as that of thev cathode 38 and that it is at substantially the same potential as that of the collector 34, respectively.

An equivalent circuitV diagram of the counter tube 10 and suitable associated circuitry is shown in Fig. 2 including pulse generator 16, blocking capacitor 66, resistors 62 and 58, potential source 60, collector 34, cathode 38, anodes 28 and 30, utilization device 18, delay device 20, and inverter amplifier 22. R1 indicates the resistance be tween the anode` 28` and conductive cylinder 26; R1 indicatesthe resistance between the anodes 28 and 30; and Rayindicates the4 resistance between. anode 30 and. conductive` cylinder 32. R1,I R1y andfRB are, in fact,l provided by resistivey cylinder Z4. Capacitors` C1 and C2 are` intended4 to show theinterelectrode capacitance between` the anodes 28 and 3l) and collector electrode 34, respectively. In the` operation of thedevice, a conduction current, i1,

may flow through the resistor R1; a displacement current, im, may owtthrough the capacitor C1; a resistive current, i2, may ow through the resistor R2; a displacement current, i132, may flow through the capacitor C2; and an electron beam current, i131, may ow to or from the anode 28. A beam current, i152, may likewise flow to or from the anode 30, and a resistive current, i3, may ow through the resistor R3. 1

The counter tub'el() lisV set for counting when both the anodes 28 and 30 are near the potential of cathode 38. The true staticA load characteristics of the counter tube 10 will be better understood with reference to the graph of Fig. 3 which illustrates a secondary-emission voltagecurrent curve 130, which the metal, used for the anodes 28 and 3i), may have. The curve 130 is thus the inverse of a secondary-emission-ratio curve. The curve 130 then is the current i111 plotted as a function of V1, V1 being the potential of anode 28. The curve 130 is likewise the same for i112 plotted asa function of V2, V2 being the potential 'of the" anode 30. All potentials are taken relative to the cathode 38, hence i3 and i132 may be plotted as a function of V1. The mechanics ofthe plot of i3 plus i112 versus V1 involves determining the magnitude of i3 plus i132 at the particular voltage `V1=V0. The fact that i3 plus i132 plotted as a function of V1 is linear and passes through the origin can be easily proven algebraically. i3 plus i111 at V1=V0 is found graphically by solving the equation is near the potential of the cathode 38. i1 is plotted as a function of V1 resulting in the line 134. This is the load line of R1 which passes through the collector potential V0 and has a slope equal to The intersections 136, 138, and 140 of curves 134 and 132 indicate the stable and unstable potentials of anode 28.

Thus the beam current must be suficiently high to produce three intersections or the anodes will have only one stable state for a given resistance and collector voltage.

1 At a given abscissa in Fig. 3, if the ordinate of the load line 134 is larger than that of curve 132, the rate of change of the potential of anode 28 with respect to time will therefore be positive. For example, Where the load line 134 intersects the curve 132 at the point 136, the potential of the anode 28 is V111. 1f the potential of anode 28 is less than V111, a displacement current will cause the potential of anode 28 to rise to the point136. The load line 134 intersects curve 132 at two other points 138 and 140 where the potentialV of theanode 28 is V1c and Vm, re-

spectively. `When the potential of the anode 28 is larger than V111, and smaller than V1.1, the rate of change of the potential of the anode 28 will then be negative, and the potential of the anode 28 Will be driven toward the point 136 by secondary emission current. When the potential ofthe anode 28 is larger than V1c and smaller than V11, the rate of change V1 with respect to time is then positive and thepotential of anode 28 will rise to the point 140 Where V'1=-1'\f11,1.` When the. potential of anode 28 is larger than V111,` the ordinate of curve 132 is larger than that:I of the load line 134, whereby'the rate of change of V1 with respect` to time is negative and the potential of anode ZS is. driven back toward the potential V111.

f 4The potential of theanode 30 when the potential of anode 28 is equal to V1u may be determined by first drawing theload line of the resistor R2, which is equal to i3 plotted as a function of V2. This is indicated by the curve 142. The sum of i3 plus i132 is then plotted as a function of V2. This is indicated by the curve 144. The load line 142 therefore intersects curve 144 at a point 146, which indicates the potential of the anode 30 where V2 equals Vzuu. f

The minimum voltage pulse amplitude of pulse generator 16 must be about equal to or somewhat greater than Vm minus V11, where Vm is the critical voltage of the anode 28 when the collector voltage is equal to V0 plus Vn,c minus Vm. There is no limit on the maximum voltage pulse amplitude; however, for a given pulse amplitude, the pulse width should be small enough to keep the potential of anode 30 below its critical potential after the collector 34 is returned to V0. The critical potential of anode 30 is shown as V21, at a point 158 in Fig. 4 which is a graph of the static load characteristic of anode 30.

If the amplitude of the pulse 68 is larger than Vlcc minus Vm, the interelectrode capacitance C1 between co1- lector 34 and anode 28 will cause the anode voltage V1 to increase from V1u to a Voltage which may be Vp which is at a point 150 on a dynamic load line 148 of resistor R1. Since at the point 150 i1 will be larger than the sum of i3, i132, and i131, the potential of the anode 28 will then rise to Vm if after the collector 34 has been returned to the quiescent value Vn, 'the potential of anode 28 is larger than V1c.

The voltage pulse width should thus be large enough to permit the anode 28 to rise to a potential greater than V11, after the `collector 34 has been returned to V0. The minimum pulse amplitude for the anode 30 is shown as Vm at a point 157 in Fig. 4. If the pulse amplitude for pulsing anode 28 is greater than V1cc--V1u and less than Vgcc- V211, the pulse width may be as large as desired although not less than the minimum pulse width. When the voltage pulse raising the potential of anode 28 is larger lthan Vm, the pulse width should then'again be small enough to keep the potential of anode 30 below Vm, when the collector 34 is returned to V0.

- As stated previously, the counter tube may be used to count negatively. This may be accomplished by applying pulses to the anode 28 to lower its voltage from a p0- tential V1m to a potential below V10, while V2 is near the potential of the cathode 38.

? The stable and critical potentials of the anode 30 when the anode 28 is near the potential of the collector 34 are shown in Fig. 4 where the sum of i3 and im is plotted as a function of V2 as indicated by a curve 152, and i1 minus i131 is plotted as a function of V2 as indicated by the voltage-current characteristic 154. i1 minus i131 may be found graphically from the curve 130 of Fig. 3, assuming i131 to be equal to zero and assuming V1 to be near the potential of the collector 34. The lower stable potential of anode 30 is therefore V2 shown at the point 156 where the curves 152 and 154 intersect. The critical potential of anode 30 is shown to be V21, at the intersection of the curves 152 and 154 at point 158. The relatively high stable potential of the anode 30 is shown at the potential Vzm where the point 160 indicates the intersection of the curves 152 and 154.

` When the anode 30 is at the potential Vzm, the potential of anode 28 may be found by drawing a load line 162 of R2. Curve 162 and a curve 164 of i1 minus i131 plotted as a function of V1 then intersect at a point 166 which gives the potential of anode 28 at V1mm. The pulsing of the anode 30 is analogous to the pulsing of the anode 28.

It was stated previously that the cathode 38 could be pulsed negatively in order to count positively instead of pulsing the collector positively.

counter tube 10 when this is done is then shown in'Fig.

The operation of 4the,

5 where V2 is assumed to be near the potential of the cathode 38, and the curves 132` and 134 are shown to a smaller scale. When the cathode 38 is pulsed negatively, the characteristic curve 132 then assumes a diierent position, shown by curve 168. Since the potential of the anode 28 remains at Vm the ordinate of the curve 134 is then larger than "the curve 168, and the potential of the anode 28 increases to the potential V1m from the point 136 on the curve 134 through the point 138 to the point 140.

The invention may be conveniently practiced with numerous dierent embodiments, another of which is shown in Fig. 6. An elongated "counter tube is there illustrated with ten illuminated areas 172 on an evacuated envelope 174; the illuminated areas may have the shape of the numbers from 0 to 9, as shown. The counter tube 170 is employed to visually indicate its state by the illumination of a given number. It is to be understood, however, that all numbers smaller than the given nurnber will also generally be illuminated. Further, zero will generally be illuminated all of the time the tube 170 is in operation. The counter tube 170, a decade counter, may be employed with other such counter tubes to accomplish such functions as frequency measurement. A brokenaway section of one end of a counter tube 170 is shown in Fig. 7 comprising the evacuated envelope 174 on the internal surface of which is coated a conductive layer 175 such as stannous chloride, and a uorescent layer 176 such as luminescent phosphor. Stannous chloride layer 175 is maintained at a potential about 1000 volts positive with respect to the cathode 38 in order to set the potential of phosphor layer 176 at about 1000 volts. The phosphor layer 176 may, however, be maintained at about this potential by numerous other methods, viz., by interposing a relatively high potential grid between the anodes and phosphor layer 176 or by coating the internal surface of the phosphor layer 17 6 with an aluminum layer and maintaining the aluminum layer at a relatively high potential.l

Inside of the envelope 174 and spaced from the phosphor coating 176 are ten anodes of which anodes 177, 178, 179, 180, 181, and 182 are visible. On one side of the anodes 177, 178, and 179, numbers 0, 1, and 2, indicated by 281, 282, and 283, are silhouetted by the metallic sheets forming the anodes whereby electrons may pass through the apertures forming the numerals indicated by 181, 182, and 183 and be converted into light by the luminescent phosphor particles 176. For this reason the anode 177 is always maintained at the potential of the collector V34 shown inside the anodes at the center of the envelope 174. The cathode 38 is illustrated inside collector 34 inside of which the filament 44 is positioned. Electrons are prevented from illuminating the phosphor particles 176 by a plurality of dielectric strips 184 which are disposed between adjacent anodes. The strips 184 and the anodes are all mounted on two dielectric rods 185 which may consist of a material known as sauereisen cement impregnated with graphite. Resistance is thus provided between the anodes to form an equivalent circuit, which is illustrated in Fig. 8.

Tube 170 in Fig. 8 is shown with circuitry necessary for its proper function in a chain of decade counters. It can be seen from Fig. 8 that the anode 177 is a connector anode because it only '.has one stable state corresponding to the potential of collector 34, to which it is directly connected. A plurality of capacitors 186 is shown connected to each of the anodes, the capacitors 186 representing a substantially greater capacitance between the anodes and the stannous chloride layer 175 Blocking v collector electrode 34. The delay-reset mechanism 187 is connected between an extra anode 190 and through ar terminal 171 to the collector electrode 34. The anode 190 is called an extra anode because it is not employed to indicate the state of the counter tube 170 in exhibiting a numeral on the luminescent phosphor coating 176, but it is only employed to reset the counter tube 170. The following counters 189 derive their input pulses 193 from the rise in potential of the extra anode 190.

The sides of the capacitors 186 not connected to the anodes are mutually joined to a terminal 191, which is maintained at a potential positive with respect to ground, for example, at a potential 1000 volts positive with respect to ground, by a source of potential 300. The terminal 191 need not be connected to potential source 300, but may be connected to any other constant potential. The terminal 191 may also be connected to the collector 34. In this case the tube operates in exactly the same -way as does the counter tube 10 of Fig. l. In the counter tube 1 70 of Fig.` 8 with the terminal 191 being connected to some tixed potential source to count positive, a positive pulse 192 may either be impressed upon collector electrode 34, or upon the terminal 191 or alternatively a negative pulse may be impressed upon the cathode 38. Conversely to count negatively, a negative pulse may be impressed upon the collector 34 or on the terminal 191, or a positive pulse may be impressed upon the cathode 38 at a terminal 294.

When the counter tube 170 is employed to count positively, in the initial state all of the anodes including the extra anode 190 are near the potential of cathode 38. If RB is the resistance between the collector 34 and the anode 178 and R9 is the resistance between the adjacent anodes 178 and 179, then the load line of the resistance R8 is illustrated in Fig. 9 by the line 194. The snm of the currents, i9, through the resistor R9, and iBq to the anode 178 may be illustrated by the curve 195. The stable points of the anode 19t) are then points 196 and 197 at potentials VS1 and V52 and the critical potential V,Lc is shown at points 200.

When the terminal 191 is connected to ground or to a point of some ixed potential, the pulse widths of the pulses which the counter tube 170 counts may be critical when the pulse amplitudes are either above or below the critical potential of the second succeeding anode to be pulsed. When positive pulses are applied to the collector, the voltage of anode 178 will instantaneously remain unchanged, but because of a displacement current, the current through the resistor R8 will rise to the point 198 on a curve 199, which is the load line of the resistor Rs when the pulse amplitude is equal to VR minus 4V0. It is thus important not to have the pulse width too great because all of the anodes will rise to their relatively high potential state if the collector 34 1s not returned to the quiescent value V before the anode having the next highest potential passes its respective critical potential Vcc. For example, before anode 179 passes above its critical potential when a pulse is impressed on anode 178 to raise its potential toward V52, the collector 34 should be returned to V0.

When the terminal 191 is maintained at ground or at some fixed potential, and the potential of cathode 38 is lowered negatively, the curve 19S will assume the form of curve 201. The ordinate of the curve 194 is then Agreater than curve 261 and the anode 178 will rise to the potential VS3. For the counter tube 170 to count negatively, the operation is analogous in that Vac is still the critical potential for the anode 178, and the potential of anode 178 must be lowered from VS2 to a potential less than Vac before the collector 34 is again returned to the quiescent value Vn. l

A counter tube of any desired modulus may thus be constructedin a most facile manner and supernumerary circuit connections necessary for transistor and vacuum tube multivibrators may be avoided by the use of plural anodes.

What is claimed is:

1. A secondary emission counter tube comprising an evacuated envelope, a thermionic cathode disposed within said envelope; a` plurality of anodes disposed successively adjacent one another at least one of said anodes being capable of emitting secondary electrons; a collector electrode disposed between said cathode and said anodes; and means providing resistance between two adjacent anodes, between one of said anodes and said cathode, and between another one of said anodes and saidcollector electrode. 2. A secondary emission counter tube comprising an evacuated envelope, a thermionic cathode disposed within said envelope; a plurality of anodes disposed succes sively adjacent one another; at least one of said anodes being capable of emitting secondary electrons; a collector electrode disposed between said cathode and said anodes; means providing resistance between two adjacent anodes, between one of said anodes and a rst point having a predetermined reference potential, and between another one of said anodes and a second point lhaving a potential positive with respect to said reference potential, said reference potential being approximately equal to the potential of said cathode; each of said anodes being capacitively con nected to said collector electrode.

3. A secondary emission counter tube circuit compris ing an evacuated envelope, a thermionic cathode disposed withinV said envelope; a plurality of anodes disposed suc cessively adjacent one another; at least one of said anodes being capable of emitting secondary electrons; a collector electrode disposed between said cathode and said anodes; means providing resistance between two adjacent anodes, between one ofsaid anodes and said cathode, and between another one of said anodes and said collector electrode; each of said anodes capacitively connected to said collector electrode; and meansfor maintaining said collector electrode at a substantially xed potential with respect to the potential of said cathode.

4. The invention as defined in claim 3, wherein said collector electrode is connected to said cathode.

5. A secondary emission counter tube circuit comprising an evacuated envelope, a thermionic cathode disposed within said envelope; a plurality of anodes disposed successively adjacent one another; at least one of said anodes being capable of emitting secondary electrons; a collector electrode disposed between said cathode and said anodes; means providing resistance between two adjacent anodes, between one of said anodes and said cathode, and `between another one of said anodes and said collec tor electrode; means for maintaining said collector electrode at a potential positive with respect to that of said cathode; and means for applying a voltage pulse between said collector electrode and said cathode, whereby the potentials of said anodes are sequentially changed. t 6. A secondary emission counter tube circuit comprislng an evacuated envelope, an elongated cylindrical cath ode disposed at the center of said envelope, a conductive cylindrical grid disposed about and spaced from said cathode to provide a collector electrode, a resistive coating disposed on the internal surface of said envelope, a plurality of annular metallic strips capable of emitting secondary electrons disposed on the internal surface of said resistive coating and spaced from one another, means for maintaining one of said annular metallic strips at substantially the same potential as that of said cathode, means for maintaining another one of said annular metallic strips at the same potential as that of said collector electrode, and means for maintaining said collector elec trode at a potential positive with respect to the potential of said cathode.

7. A secondary emission counter tube circuit comprising an evacuated envelope, an elongated cylindrical thermionic cathode disposed at the center of said envelope, a cylindrical grid-type collector electrode disposed concentrically about said cathode, a plurality of annular metallic strips capable of emitting secondary electrons disposed about said collector electrode and axially spaced from each other, said strips'being connected to at least one resistive rod, said rod projecting axially parallel to and outside of said collector electrode, means for maintaining one of said annular metallic strips at the same potential as that of said cathode, and means for maintaining another one of said annular metallic strips and said collector electrode at a potential positive with respect to that of said cathode.

8. The invention as defined in claim 7, wherein a luminescent dielectric coating is disposed on the internal surface of said envelope, and said annular metallic strips are provided with apertures forming predetermined characters, whereby the stable state of said counter tube at any time may be determined by observing the characters illuminated on said dielectric coated surface of said envelope.,

9. A secondary emission counter tube circuit comprising an evacuated envelope, a thermionic cathode disposed within said envelope, a plurality of anodes at least one of which is capable of emitting secondary electrons disposed successively adjacent one another; a collector electrode disposed between said cathode and said anodes; means providing resistance between two adjacent anodes,

' between one of said anodes and said cathode, and between another one of said anodes and a point of potential positive with respect to that of said cathode; a first terminal junction connected to said collector electrode; a second terminal junction; each of said anodes being capacitively connected to said second terminal junction; means for maintaining said collector electrode at a quiescent potential positive with respect to that of said cathode; and

means for applying a voltage pulse between said cathode and one of said terminal junctions.

10. A secondary emission counter tube circuit comprising an evacuated envelope, an elongated cylindrical thermionic cathode disposed at the center of said envelope, a cylindrical grid-type collector electrode disposed concentrically about ysaid cathode, a plurality of annular metallic strips capable of emitting secondary electrons disposed about said collector electrode and axially spaced from each other, said strips being connected to at least one resistive rod, said rod projecting axially parallel to and outside of said collector electrode, means for maintaining one of said annular metallic strips at the same potential as that of said cathode, means for maintaining another one of said annular metallic strips and said collector electrode at a potential positive with respect to that of said cathode, a conductive coating disposed on the internal surface of said envelope, the capacitance between said collector electrode and said anodes being substantially different than the capacitance from said anodes to said conductive coating, and a luminescent dielectric coating disposed on said conductive coating, said annular metallic strips being provided with apertures forming predetermined characters, whereby the stable state of said counter tube at any time may lbe determined Iby observing the characters illuminated on said dielectric coated surface of said conductive coating.

References Cited in the file of this patent UNITED STATES PATENTS 1,987,136 Sukumlyn Ian. 8, 1935 2,090,001 Hamacher Aug. 17, 1937 2,141,838 Farnsworth Dec. 27, 1938 2,640,169 Nevin May 26, 1953 2,645,741 Westervelt et al July 14, 1953 2,728,815 Kalfaian Dec. 27, 1955

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