US2558178A - Glow tube counter - Google Patents

Description

June 26, 1951 G. E. HAGEN GLOW TUBE COUNTER 2 Sheets-Sheet 1 C400) pu/s' to Stage 2 Zsai Filed Nov. 15, 1948 INPUT Pulse INVENTOR. 6L EN/V 6. H4 GEN ,INPUT PULSCS VOLMGE June 26, 1951 G. E. HAGEN 2,558,178

GLOW TUBE COUNTER Filed Nov. 13, 1948 2 Sheets-Sheet 2 INPUT 0 Pulse 7 30 3/ i Z i 44 453 30 mam Puke to flaxrsfa e INVENTOR. 64am 5. unaeu Jrromv r Patented June 26, 1951 GLOW TUBE COUNTER Glenn E. Hagen, Redondo Beach, Calif., assignor to Northrop Aircraft, Inc., Hawthorne, Califi, a

corporation of California Application November 13, 1948, Serial No. 59,851

Claims.

My invention relates to electronic counters, and. more particularly to counters utilizing operational characteristics of ionic glow tubes to count pulses.

Electronic counting circuits are Well known and are commonly used in experimental physics and in industrial production controls.

In such devices, an electronic equivalent of a gate or switch is incorporated, and for this switch ordinary multi-element hot cathode electron emitting type vacuum tubes are commonly utilized. The nature of counting circuits utilizing such tubes is such that they require many circuit elements and a relatively large power supply. The use of many circuit elements increases the probability of circuit failure and tends to increase the time of preoperation testing. Two separate power sources are usually required; one for the anode, and one for heating the cathodes. Such circuits are often called flip-flop circuits.

It is an object of the present invention to provide a flip-flop circuit requiring only one voltage source, from which the current demand is relatively low.

It is another object of the present invention to provide a switch, gate or flip-flop circuit using non-rectifying elements.

It is still another object of the invention to provide an ionic flip-flop.

And it is a further object of the invention to provide a simple binary counter.

I have found that two electrode cold cathode gaseous ionic tubes, commonly known as glow tubes, can be utilized in counting circuits due to the fact that the voltage between electrodes to cause the glow tube to remain in a conducting state once it is ignited, 1s less than the voltage necessary to start the discharge in the tube.

The difference between the operating and striking voltages of glow tubes is used to create the two stable conditions required for an electronic counting circuit.

My invention will be more fully understood by reference to the drawings, in which:

Figure 1 is a circuit diagram of one binary countin stage embodying the present invention.

Figure 2 is a graph showing voltage conditions at a point in the circuit of Figure 1.

Figure 3 is a circuit diagram of a binary counting stage embodying the present invention and utilizing special glow tubes.

Figure l is a circuit diagram of input stage 2" of a binary counter having similar stages 2 2 2 2 only the input stage being shown, and

willbe first referred to. A

Each stage includes seven small two electrode cold cathode glow tubes GT of the parallel electrode type known in the trade under the desig-v nation NE-2. This type of glow tube is preferred, and is neon filled. Any other type of ionic glow tube, however, having a substantial difference between striking and operating voltages will be satisfactory.

Three of the seven tubes, GT1, GT2 and GT3 are connected in series as are another three tubes GT4, GT5 and GT6. Tubes GT3 and GT6 are connected by ground wire I, which latter is grounded. The other ends of the tube series GT1, GT2 and GT3, and the series GT4, GT5 and GT6 are connected together through a condenser 2.

Connections GT2: and GTss between tubes GT2 and GT3 and between tubes GT5 and GT6, respectively, are connected by across connection containing two separate input condensers 4 and 5. A pulse input line 6 is connected between condensers 4 and 5. When multiple stages are used in a binary counter, the output of one stage is connected to pulse input line 6 of the next stage.

The tubes to be visible for evaluation of the count, are chosen to be tubes GT3 or GT6, al-

" GT3 and GT6, respectively. In order that only one of the tubes GT3 and GT6 may be seen at a time, a slide 8 is provided having slide apertures 9 and 10 therein spaced apart a distance less than the spacings of apertures A3 and As. Movement of slide 8 will register one or the other of slide apertures 9 or II] with one, and only one, of the viewing apertures A3 or A6 so that only one tube can be seen at one time. The one tube seen is the visual counting tube, and, as will be shown later, will either .be on or ofi, thus indicating the binary counting number 0 or I for the stage.

A positive voltage of 240 volts is supplied to a voltage line II, this line connecting with a common resistor I2 of 150,000 ohms, the latter being centrally connected at the other end to a GT1 resistor l3 and to a GT4 resistor l4 connected to the respective tubes GT1 and GT4 across the con- 3 denser 2. Resistors l3 and I4 are each of 100,000 ohms resistance.

Voltage line I l is also connected through a large GT7 resistor I (5 megohms) to an output glow tube GT7, the other side of which is connected by line 16 to the junction of resistor 14 and the condenser 2 connection with tube GT4, this junction being designated as point C. Point C and tube GT7 are connected to ground through a zeroing switch 11 and switch resistor IS.

A carry pulse output line 20 is connected between the GT7 resistor and tube GT7.

To aid in the description of the operation of the counter stage shown in Figure 1, the point in the circuit corresponding to point C in the first series of tubes is designated point D. The junction of resistors l2, l3 and I4 is designated point E. The condenser 5 attachment to connection GT55 is shown as point F, and the condenser 4 connection to connection GT2'3 is designated as point G.

The preferred tubes chosen have an operating voltage of approximately 60 volts and will strike at approximately 75 volts, providing a differential of 15 volts. When the 240 volt supply voltage is first applied to the circuit the voltage across either series of tubes may be sufficient to strike them all. Thus, tubes GTi, GT2, GT3, GT4, GT5 and GT6 Will all become conducting. Immediately after striking, the voltage across any one tube drops to 60 volts. Thus, when all tubes are conducting, the voltage at points C and D of Figure 1 will be 180 volts. Closing the zeroing switch causes a decrease in voltage at point C and a smaller decrease in voltage at point E. The decrease in voltage at point C is sufficient to extinguish tubes GT4, GT5, GT6 if they are lit. When the zeroing switch is once again opened the voltage at C rises and hence a rise in voltage at D takes place due to the action of condenser 2. Since the voltage at point D was initially larger than the voltage at point C, tubes GT1, GT2, GT3 will ignite before GT4, GT5, GT5. Once the unilateral operating conditions are established, they will remain unilateral.

Since the characteristics of glow tubes vary slightly, it is possible, however, that, for example, tubes GT4, GT5 and GT6 might strike before tubes GT1, GT2 and GT3 when the supply voltage is first applied. The voltage at point E and point D would then drop quickly to 204 volts and tubes GT1, GT2 and GT2 would not have sufficient voltage across them to strike and would remain ofi. In any case, initial counting conditions require one series out, the other series lit.

The counter operates with respect to binary numbers. Thus, in operation either tubes GT1, GT2 and GT3 or tubes GT4, GT5 and GT6 will be conducting. At no period of time after the original setting, will all tubes be conducting nor will all tubes be non-conducting. The counter stage shown in Figure 1 will contain the binary number 0, for example, when tubes GT4, GT5 and GT6 are conducting, and contain the binary number I when tubes GT1, GT2 and GT3 are conducting, these numbers being indicated by viewing tube GT3.

The input pulses to the counter stage are applied between condensers 4 and 5. Assume that tubes GT4, GT5 and GT6 are conducting, i. e., the counter stage has the number zero in it. In this case, tube GT3 will be out. The voltage at point E is 204 volts, at point C it is 180 volts, and at point D it is 204 volts. There is a. 24 volt charg on condenser 2. 1

When a negative pulse is applied at the input, between condenser 4 and 5, it causes a decrease in voltage at point G since condenser 4 cannot charge through either tube GT2 or tube GT3 due to their non-conducting condition. The decrease in voltage at point G, however, is suflicient to cause tubes GT1 and GT2 to strike. The negative input pulse causes little change in voltage at point F since condenser 5 can quickly (time depends on the size of condenser 5) charge up through tubes GT5 and GT6, due to their conducting condition.

After tubes GT1 and GT2 strike, the voltage drop across them decreases to volts and thereby increases the voltage across tube GT3 sufficiently to cause it also to strike. The voltage at point D quickly becomes volts and the resistance combination [2, l3 and I4 is such that the decrease in voltage at point D is reflected to point C and is sufiicient to extinguish tubes GT4, GT5 and GT6. Thus, one negative pulse at the input has caused the counter stage to change from a condition where tubes GT1, GT5 and GT6 are conducting and tubes GT1, GT2 and GT3. are nonconducting, to a condition where tubes GT1, GT2 and GT3 are conducting, and tubes GT4, GT5 and GT5 are non-conducting. The viewing tube GT3 is now lighted and indicates the numeral I.

It has been found experimentally that a positive pulse input causes an identical result as described for a negative pulse input to the counter stage.

Another pulse applied to the input 6 causes the counter to return to its original conditions where tubes GT4, GT5 and GT6 were conducting and tubes GT1, GT2 and GT3 were non-conducting.

The tube GT7 and resistor I5 control the carry pulses to the next counting stage. Referring to Figure 2, the voltage at point C of Figure 1 before the first input pulse is 180 volts, since tubes GT4, GT5 and GT6 are conducting. The first input pulse strikes tubes GT1 and GT2, and the voltage at point D decreases rapidly and causes the voltage at point C to also fall rapidly. Tubes GT4, GT5 and GT6 are extinguished and the voltage at point C tends to rise towards a stable condition of 204 volts as condenser 2 charges through resistors I2 and 14. However, the initial decrease in voltage at point C, caused by input pulse number one, is sufficient to cause tube GT7 to strike. Tube GT7 strikes when 75 volts are impressed across it and operates with a voltage difference between terminals of 65 volts. When tube GT7 conducts, the voltage difierence across the large resistor 15 is sufficient to quench tube GT7. Before tube GT7 can restrike, the condenser 2 has charged up sufficiently to bring the voltage at point 0 beyond the point at which tube GT7 strikes. The voltage at the carry pulse output 20 remains constant except when the tube GT7 momentarily conducts, at which time a negative pulse is emitted to the next stage.

The second input pulse causes tubes GT4, GT5 and GT6 to become conducting, hence the voltage at point C drops from 204 volts to 180 volts as indicated at input pulse position 2 in Figure 2.

Initially it was assumed that tubes GT4, GT5 and GT5 were conducting when the counting stage contained the binary number zero. The circuit shown in Figure 1, therefore, passes a carry pulse when the number in the counter changes from zero to one and is characteristic of a counter that counts in a subtractive fashion.

By placing resistor 15 and tube GT7 between.

point D and the supply voltage line I I the carry pulse output from there will occur when the number content in the counter stage changes from one to zero and is characteristic of additive counting.

With a resistor i5 and a tube GT7 combination placed on each side of every counter stage and with proper switches located in the carry pulse circuits, either additive or subtractive counting can be obtained.

Furthermore, additive or subtractive counting can be obtained in accordance with the position of slide 8 Which, in a multistage counter, will expose either tube GT3 or GTG in all stages at once. In the position shown in Figure l subtractive counting is accomplished when tubes GT4, GT5 and GT6 are lit first in each stage and tube GT3 is exposed. When tube GT6 is viewed, subtractive counting is shown under the same circumstances using the output circuit shown in solid lines.

A modification of the invention is shown in Figure 3 where special glow tubes are utilized to reduce the number of tubes needed. As in Figure 1, the circuit of Figure 3 shows a single stage of a binary counter.

In this case, only three glow tubes are needed. Two of the tubes, tube A and tube 3 are three electrode glow tubes such as may be visualized by making the connected electrodes of tubes GT1 and GT2, or of tubes GT4 and GT5 in Figure 1, a single electrode, and then placing the other electrodes of the two tubes in a single envelope. For the purposes or" this discussion, the striking and extinguishing voltages of each outside electrode 3B and 3th]. of the tubes A and B, with respect to the middle electrode iii of each tube, is assumed to be the same as that of the GT tubes used in the circuit of Figure 1.

In the circuit of Figure 3, the outside electrodes 39 of tubes A and B are connected together and to a source line 32. The two outside electrodes Slla of tubes A and B are connected together through a cross condenser 34.

One electrode 38a is also connected to one end of a resistor 35, and the other electrode 36a is connected to one end of a resistor 38. The other ends of resistors 35 and 35 are connected together and to ground through a ground resistor 31. The junction of the three resistors 35, 36 and 31 is designated as point X, the junction of the resistor 35 with electrode Sea of tube A and across condenser 34 is termed point Y, and the junction of the resistor 35 with electrode ita of tube B and cross condenser 36 is designated point Z.

One electrode of a two electrode carry pulse glow tube lli is connected to point Z and the other electrode of tube 40 is connected to ground through output resistor ll The carry pulse output line 42 comes from between output resistor 4! and tube M3.

The input pulse line 43 is connected between input capacities 44 and 45, the other side of'these capacities being connected to the middle electrodes 3! of tubes A and B respectively.

In operation, the potential in source line 32 is maintained at a positive voltage slightly higher than the operating voltage of the tubes. Assume that when tube #A is conducting and tube #B is non-conducting, the binary number zero is in the countingstage, and that the binary number one is in the counting stage when the conditions are reversed. By properly positioning switches to points Y or Z either number can be set into the counter. Assume that the counting stage of Figure3 has the number zero in it. Since:

zeroin tube #A is conducting, a current is flowing through resistors and 3'! making the voltage at point X and hence at point Z higher than ground, and the voltage at point Y higher than point X. y

The next positive input pulse causes a. current flow between the striking electrode and the more negative electrode of tube #3 and hence causes tube #13 to become conducting. When tube #13 becomes conducting, point Z has a rise in voltage. Since condenser 34 cannot charge immediately, the voltage at point Y also rises and causes tube #A to extinguish. The rise in voltage at point Z is not sufficient to cause tube to strike.

Thus, one input pulse has caused the counting stage to contain the binary number one, and no carry pulses have been transmitted.

The next positive input pulse causes tube #A to become conducting, tube #3 to become nonconducting, the voltage at point Z to rise sufficiently to cause tube it to strike, and thereby send a positive carry pulse to the output. As in the embodiment of Figure 1, either tube A or B may be viewed to obtain the stage count.

The circuit of Figure 3 has all of the advantages of the glow tube counter shown in Figure 1, and in addition, the number of tubes necessary for operation is decreased. Both circuits can be incorporated in such counting devices as an additive-subtractive counting counter, a simultaneous transfer device, electronic differential, etc.

By using ionic glow tubes instead of electronic vacuum tubes, this invention has the advantages of less cost, smaller space requirements, and lighter weight. Since ionic glow tubes require no current for heating a cathode and require less plate current for operation, the power supply for their operation is smaller, lighter and less expensive than that required for an electronic vacuum tube counter performing the same functions.

From the above description, it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into efiect, and the invention is, therefore, claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

What is claimed is:

1. A flip-flop circuit comprising a first plurality of two electrode glow tubes connected in series. a-second plurality of two electrode glow tubes connected in series, a voltage source, a main resistance connected at one end to one side of said voltage source. a first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of tubes, a second plurality resistance connected to said other end of said main resistance and to an end electrode of said second plurality of tubes, a capacity connecting said end electrodes, the op- 7, posite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, said glow tubes having sub stantially the same striking voltages higher than the operating Voltages thereof, and said plurality resistances being substantially equal so that each plurality of tubes will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input, and a capacity between said input and a corresponding intermediate electrode in each plurality.

2. A flip-flop circuit comprising a first plurality of two electrode glow tubes connected in series, a second plurality of two electrode glow tubes connected in series, a voltage source. a main resistance connected at one end to one side of said voltage source, a first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of tubes, a second plurality resistance connected to said other end of said main resistance and to an end electrode of said second plurality of tubes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, said glow tubes having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality of tubes will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input, a capacity between said input and a corresponding intermediate electrode in each plurality, and an output line connected across one of said plurality resistances and said main resistance.

3. A flip-flop circuit comprising a first plurality of two electrode glow tubes connected in series, a second plurality of two electrode glow tubes connected in series, a voltage source, a main resistance connected at one end to one side of said voltage source, a first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of tubes, a second plurality resistance connected to said other end of said main resistance and to an end electrode of said second plurality of tubes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, said glow tubes having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality of tubes will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input, and a capacity between said input and a corresponding intermediate electrode in each plurality, an output line connected across one of said plurality resistances and said main resistance, an output glow tube in said output line and operated by the voltage drop across said latter resistances, and means for creating an output pulse when said output glow tube is operating.

4. A flip-flop circuit comprising a first plurality of two electrode glow tubes connected in series, asecond plurality of two electrode glow ill) tubes connected in series, a voltage source, a main resistance connected at one end to one side of said voltage source, a first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of tubes, a second plurality resistance connected to said other end of said main resistance and to an end electrode of said second plurality of tubes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, said glow tubes having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality of tubes will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input, a capacity between said input and a corresponding intermediate electrode in each plurality, an output line connected across one of said plurality resistances and said main resistance, an output glow tube in said output line and operated by the voltage drop across said latter resistances, means for creating an output pulse when said output glow tube is operating, and means for viewing at least one of the glow tubes in one of said pluralities only.

5. A flip-flop stage comprising a first plurality of two electrode glow tubes connected in series, a second plurality of two electrode glow tubes connected in series, a voltage source, a main resistance connected at one end to one side of said voltage source, a first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of tubes, a second plurality resistance connected to said other end of said main resistance to an end electrode of said second plurality of tubes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, said glow tubes having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality of tubes will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input, a capacity between said input and a corresponding intermediate electrode in each plurality, an output line connected across one of said plurality resistances and said main resistance, an output glow tube in said output line and operated by the voltage drop across said latter resistances, means for creating an output pulse when said output glow tube is operating, means for viewing at least one of the glow tubes in one of said pluralities only, and means for shifting said viewing means from a glow tube in one plurality to a glow tube in the other plurality.

6. A plurality of flip-flop stages in accordance with claim 5 wherein the input of one stage is connected to be energized by the output pulse from a prior stage.

'7. A flip-flop circuit comprising a first plurality of cold glow tube electrodes connected in series in an ionizable gas, a second plurality of cold glow tube electrodes connected in series in an ionizable gas, a voltage source, a main resistance connected at one end to one side of voltage source, a first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of electrodes, a second plurality resistance connected to the last mentioned end of said main resistance and to an end electrode of said second plurality of electrodes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, adjacent electrodes of each plurality having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality series of electrodes will strike at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input line, and a capacity between said input line and a corresponding intermediate electrode in each plurality, whereby a pulse applied to said input line will strike the non-operating plurality of electrodes and extinguish the operating plurality of electrodes.

8. A flip-flop circuit comprising a first plurality of cold glow tube electrodes connected in series in an ionizable gas, a second plurality of cold glow tube electrodes connected in series in an ionizable gas, a voltage source, a main resistance connected at one end to one side of voltage source, a first. plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of electrodes, a second plurality resistance connected to the last mentioned end of said main resistance and to an end electrode of said second plurality of electrodes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, adjacent electrodes of each plurality having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality series of electrodes will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input line, a capacity between said input line :and a corresponding intermediate electrode in each plurality, whereby a pulse applied to said input line will strike the non-operating plurality and extinguish the operating plurality, and an output line connected across one of said plurality resistances and said main resistance.

9. A flip-flop circuit comprising a first plurality of cold glow tube electrodes connected in series in an ionizable gas, a, second plurality of cold glow tube electrodes connected in series in an ionizable gas, a voltage source, a main resistance connected at one end to one side of voltage source, a, first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of electrodes, a second plurality resistance connected to the last mentioned end of said main resistance and to an end electrode of said second plurality of electrodes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, adjacent electrodes of each plurality having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality series of electrodes will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input line, a capacity between said input line and a corresponding intermediate electrode in each plurality, whereby a pulse applied to said input line will strike the non-operating plurality and extinguish the operating plurality, an output line connected across one or" said plurality resistances and said main resistance, and an output glow tube in said output line and operated by the voltage drop acros said latter resistances.

10. A flip-flop circuit comprisin first plurality of cold glow tube electrodes connected in series in an ionizable gas, a second plurality of cold glow tube electrodes connected in series in an ionizable gas, a voltage source, a, main resistance connected at one end to one side of voltage source, a first plurality resistance connected to the other end of said main resistance and to an end electrode of said first plurality of electrodes, a second plurality resistance connected to the last mentioned end of said main resistance and to an end electrode of said second plurality of electrodes, a capacity connecting said end electrodes, the opposite end electrodes of each of said pluralities being connected together and to the other side of said voltage source, adjacent electrodes of each plurality having substantially the same striking voltages higher than the operating voltages thereof, and said plurality resistances being substantially equal so that each plurality series of electrodes Will strike at substantially the same voltage and operate at substantially the same voltage, said resistances being evaluated to prevent one plurality from striking when the other is operating, a pulse input line, a capacity between said input line .and a corresponding intermediate electrode in each plurality, whereby a pulse applied to said input line will strike the non-operating plurality and extinguish the operating plurality, and means for viewing the glow between at least one pair of electrodes in one of said pluralities only.

GLENN E. HAGEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,329,048 Hullegard Sept. '7, 1943 2,379,093 Massonneau June 26, 1945 2,401,657 Mumina June 4, 1946 OTHER REFERENCES Wynn-Williams, Use of Thyratrons for High Speed Automatic Counting; Proc. Royal Soc. Series A, July 2, 1931, vol. 132, pp. 295-310, especially Fig. 50 on page 304 (copy in Sci. Lib.),

A. W. Hull, Hot Cathode Thyratrons, Part II. Gen. Elec. Rev., vol. 32, pp. 390-399, especially Figure 41 on page 398 (1929) (copy in Sci. Lib.).

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