US2498708A - Electric counting circuits - Google Patents

Description

Feb; 28', 1950 AHrREEvEs,

ELECTRIC coummc cracuns Filed July 21', 1948 3 Sheets-Sheet 1 .F/GZ; 17-44 Inventor film #M far/ o Attorney 2EML708 A.H;REEVES mmcrmm commas slmrns Fhb.28,1950

3 Sheets-Sheet 2 Filed July 21, 1948 I nvemor 5%, M KM Attorney Feb. 28, 1950 A. H, REEvEs 2,498,708

' ELECTRIC COUNTING CIRCUITS Filed July 21, 1948 k 3 sheets-sheet 5 Inventor Attorney Patented Feb. 28, 1950 7 UNITED. STATES PATENT -OFFICE ELEC'TVRI'Q ofii itifizdomomrs Alec Harley Reeves, London, England, assignor to International Standard Electric Corporation, New York, N. Y a corporation of Delaware Application July 21, 1948,"Serial No. 39,936 InGreatBritain July 22, 1947 '4 Claims. (01. smarts) This invention relates to electronic counting devices using gaseous discharge tubes.

In my copending applications bearing Serial Numbers 777,815, 777, 816, respectively, both filed October 3, 1947, I have described counting circuits using gaseous discharge tubes where the electrodes are arranged so as to provide a number of discharge gaps.

In one application of such a device, a potential is applied between the two electrodes of each gap, and the anode electrodes of the gaps may be connected together inside or outside, the tube, likewise the cathodes.

It is arranged that the said-potential, which may be supplied from a battery, is insufiicient to initiate a discharge across any gap, but is sufficient to maintain a discharge once begun.

Pulses of the same polarity as the battery are applied across all the gaps in commonand the combined potential of the battery and the pulse will fire one gap only (called the starting gap) when the gas in the tube is not ionised. I

. A first pulse applied to the tube will fire the starting gap which will continue to discharge owing to the battery potential. A second pulse will be able to fire another gap adjoining the starting gap owing to the'migration-of the ionisation of-the gas atmosphere in the tube, from the starting gap to the adjoining gap. A third pulse will fire yet another gap due to the migration of gas ionisation to this gap from the adjoining gap secondly fired.

The sequence will continue till all the gaps are fired from successive pulses and arrangements are made on the firing of the last gap, to procure a voltage drop which extinguishes all the discharges. I

. It is a feature ofthese devices that if it is desired to operate the tube in a series of gap sequences, the time between pulses must be sufficient for ionisation to collapse in the absence of discharges in the tube, so that after all gaps have been fired and extinguished together, the next pulse will only operate the starting gap. The starting gap and no other gap will then be fired from the next pulse after the extinguishcan function is therefore limited, unless special means are provided as described in my said oo- 2 I pending application Serial No. 777,815 to insert an'interval equal to the de-ionising time between. the final .pulse of one sequence and the starting pulse of the next sequence.

It is proposed to provide a counting device,

using a gaseous dischargetube where there is 1 no battery potential applied between pulses to maintain the discharge ingaps once they have 'been fired and in which the pulse repetition rate which may be applied, is raised by the reduction of de-ion-ising time due to the complete extinguishment of all discharges betweenpulses as compared with the time required for deionisation when the discharges are maintained by a battery between the pulses of a train.

The invention consists of a circuit arrangement'for a cold cathode gas discharge tube having three or more separate anode-cathode discharge gaps so arranged that ionisation of the gas in the vicinity of a gap due to a discharge across that gap lowers the potential needed to fire an adjacent unfired gap, the tube being so constructed and the gaps so connected and interconnected that when a series of pulses are applied to the gaps in parallel, the gaps will fire in turn, the last gap at least, firing alone.

Certain embodiments of the invention will now bedescribed in relation to the accompanying drawings in which- Fig. 1 is a circuit diagram of a counting device using a cold cathode gas discharge tube having several discharge gaps in whichthe gaps are fired successively from recurrent pulses, each gap re-firing on each pulse of a pulsetrain once it has been initially fired, there being no main taining battery.

Fig. 2 is a circuit diagram of a counting de-.- vice using a cold cathode gas discharge tube having several discharge gaps in which the gaps are fired successively from recurrent pulses, each gap firing once only during each pulse train,

there being no 'maintaining battery, due to the action of an additional cathode as compared withthe tu'be illustrated in Fig. 1, co-operating with the anode. I

Fig. 3 is a circuit diagram of counting device employing a cold cathode gas. discharge tube having a large number of gaps which can be used instead of the circuit of Fig. 2 where it is required to count pulses to a large radix, having an additional cathodeas in thetube illustrated in Fig. 2 but co-operating with a second anode.

Figs. 4 and 5 are diagrammatic plan and ele-j vation respectively of a method of construction gasses of a tube of the type used in the device illustrated in Fig. 3.

In Fig. 1 is a gas tube, with common anode (strip or wire) 2 connected through resistor 3 to ground, is an indented cathode with equal spacings between points, and with equal gaps to the anode except at a starting gap 4, which is slightly shorter. 5 is connected to ground through resistor 6. l is an extra cathode the same distance from the anode as are the points of the indentation of cathode 5 except a gap 4,.

and with the same spacing from the last point on 5 as the distances of the points on 5, one from another. 8 is a third cathodeconsisting of a small plate, also at the same distance from the anode as the points on 5 (except 4) and with its left-hand edge at the same spacing from 1 as the inter-point spacing on 5.- I isconnected to ground through a resistor 9 shunted by a small condenser HI. 8 is connected to ground via a resistor H and one winding (hereinafter'called the primary winding) of a pulse transformer l2.

Resistor H and the primary winding of I2 are shunted by a small condenser 53 (only a few pf.) and the primary winding of I2 is shunted by a rectifier M. The other winding of I2, (hereinafter'called the secondary winding), shunted by impedance [5, gives output pulses at terminals l6.

A rectifier H, in series with battery I8 is connected between anode 2 and cathode 5.

In the following description, in describing'the discharges which take place between the oathodes of a tube and its anode 2, or anodes, the expression fire will be used to indicate the inception of a discharge and when one of the said cathodes or a part, point or indentation thereof is said to be firing or discharging it will indicate that a discharge is initiated'or is taking place between such cathodes, part, point or indentation and the anode or anodes of the tube, the reference to the anode or anodes bein omitted for the sake of brevity where this can be done without ambiguity.

The input pulses to be counted are applied with negative polarity at terminal I9, and thence pass to cathode 8 via a blocking condenser '20. Terminal i9 is alsoconnected; to cathode 5 via a small delay network 22, and condenser 2|, and to'"-cathode 1 via network 22, resistance 6 and the condenser-resistor combination ll), 9. 22 may'consist for example, of inductances 23, 24 with condensers 25, 25, its delay time is greater than the build-up time of the leading edge of the input pulses, but less than the pulse dura tion. The input pulse amplitude is such that in the absence of ionisation of the gasin the tube, only the shorter gap 4 will strike.

The rectifier l4 connected across the primary winding of transformer I2 shunts the input pulses from terminal 19 (which would otherwise have to pass through this winding on their way to cathode 8), and prevents them from reaching output terminals l6. s

Let a first input pulse be applied at l9. Gap 4 will fire and the discharge ,will be maintained duringthe pulse duration'and on cessation of the pulse the discharge through 4 will immediately cease, as there isv no maintaining battery. If the next pulse arrives before the ionisation of the gas in gap 4 has had time to die away (e. g. within several microsecs, or less), the next,

as re-flring 4 since the ionisation of the gas will have spread from gap 4 to this adjoining gap. Both discharges will then go out when this second pulse ceases. The third pulse will fire the first three points from the left and so on, until all the indentations on 5 fire at once, on some later pulse} and cathode, 5, superimposed upon the voltage of battery 18 the latter being connected so as to oppose the voltage derived from the pulses.

The potential of battery I8 is adjusted so that the peak of the input pulse just passes current through I! when all the points on 5 fire together, and rectifier ll is connected in the direction such that when less than the full number of points on 5 fire a greater current will pass through it.

When fewer gaps are discharging, therefore, the rectifier i'l, beingin a conducting condition, will be virtually in shunt across anode 2 and cathode 5 so as to pass current at these times, which, together with the current flowing through the parallel path between anode 2 and cathode 5, will equal approximately the current flowing between anode and'cathode when all gaps are discharging.

All this current passes through resistances 3 and 6, thus limiting the input peak volts between 2 and 5 toa substantially constant value thereby preventing the variable voltage drop which would take place but for the insertion of rectifier I1 and battery I8, as diilerent numbers of points on 5 fired, on succe'ssivepulses.

The degree of voltage stabilisation given by rectifier I! is such that it will maintain a relatively stable voltage over the range of currents passed through the tube between the condition when no discharge is taking place on the one hand and whenall the points of cathode 5 are discharging on the other hand. At the latter point the rectifier becomes non-conducting and further rises in current through the tube will cause a drop in the peak voltage of the pulses applied to the tube which will not be compensated by the rectifier l1.

When all the points on 5 have fired, the next pulse will fire I, and-also all the points of 5. The

condenser 10 and the resistor 9 have values such and terminal l9 whereas cathodes 5 and l are connected to I 9 via the delay network 22.

The pulse will therefore T reach 8 before it reaches" cathodes '5"and |,"by an amount equal to the delay of delay netw0rk'22 which is greater than the time taken by the pulse to reach its pealg amplitude but less than the pulse duration.

As 8 has a relatively' larg'e' surface a current will tendto flow between} and 2 as the pulse voltage builds up. This current, which flows through the common anode load 3 will lower the voltage at anode 2 at the time of the pulse peak and this will limit the current rise between cathode 8 and anode 2, an equilibrium being quickly reached at a point Where the discharge across this gap is just maintained.

It is arranged that this equilibrium is reached before the delayed pulse reaches the other cathodes 5 and and it is also arranged that the voltage of anode 2 at the equilibrium aforesaid, is insufficient for any of the points of cathode (even gap 4) to fire, and cathode I is prevented from firing in any event by virtue of the charge in condenser l0.

Cathode 8 .has a time constant circuit consisting of a condenser l3 and a resistance connected in the path along which the pulses reach cathode 8.

The next pulse cannot re-fire 8, on account of the charge collected on condenser l3 the timeconstant of |||3 being several pulse spacings:

With the exception of gap 4, the only cathode point now having enough residual ionisation for a re-fire to be possible is next to 8 which has just been fired, the right-hand point on 5 being twice the distance from 8 as is cathode and being substantially de-ionised since 1 has not fired on the last pulse. But I cannot re-fire because of the charge still remaining on ID. Therefore only the starting gap 4 will fire, and the sequence of events will start again. By the time that I or 8 are due to re-fire, the charges on I and I3 will have leaked away substantially to zero-so they fire as in the first sequence.

The fact that the anode-cathode voltage drops completely to zero between pulses speeds up the de-ionising time, as compared with devices where extinguishment is effected by a mere drop in volts (not down to zero) due to a surge of current through the last electrode to fire.

In devices using a tube and a battery which maintains the discharges between pulses, extinguishment of the discharges in the tube, after all its points have been fired, is achieved by a current surge which produces a voltage drop in a common load sufiicient to lower the voltage to the point at which the discharges cannot be maintained, the last electrode, the firing of which causes this surge, must have a relatively large smooth surface and where the tube has a large number of gaps passing a large current when discharging, it may be difficult to design a last electrode, capable of passing a sufiiciently larger current to produce the voltage drop necessary to extinguish the discharges. In the case of cathode 8, in this embodiment of the invention, the current surge need only be sufiicient to cut the peak of the pulse below the voltage necessary to initiate a discharge across the points of cathode '5. Cathode 8 can therefore be relatively small and this is another advantage of this arrangement.

The counting function of the device is achieved by the delivery of a pulse through transformer I2 to terminals |5, every time cathode 8 fires, which is once in every pulse train.

The radix of the count is a number equal to the number of firing points on cathode 5 plus cathodes 1 and 8 as all these points strike once in the sequence of discharges in the tube, I.

In Fig. 2 a gas tube 21 has a common anode 28 consisting of a wire or strip, connected to ground through resistor 29. A cathode 3| with shorter gap 30 at one end, is an indented cathode as in Fig. 1. Cathodes 32 and 33 are of the same design as l and 8 respectively of Fig. 1. An extra cathode 34, consisting of a wire or strip, is either parallel to 28, or inclined to it at a slight angle so as to make the gap from 34 to 23, slightly bigger at the left hand end than at the right hand, 34 has a projecting point 33 at the righthand end giving a somewhat shorter gap at 23 at this end than at other parts of the cathode 34. Cathode 3| is connected to ground via a resistance 41. 34 is connected to ground via resistance 35. 32 is connected to ground via resistance 31; and 33 is connected to ground via a resistance 33 and one winding of a pulse transformer 4| in series with resistance 39. Another Winding of transformer 4| is terminated by impedance 42, and output pulses are obtained at terminals 43.

31 is shunted by small condenser 38, and resistance 39 in series with one winding of transformer 4| is shunted by condenser at, as in Fig. 1. Positive input pulses are applied at terminal 44, and thence to anode 23 via a condenser 45.

The design and constants are such that an input pulse will always fire the gap between anode '23 and point 36 on cathode 34. A glow will then very rapidly spread along the surface of cathode 34, covering the entire length before the end of the duration of the pulse applied at 44. It is also arranged that the input pulses between 23 and 3| are insufficient to fire any point on cathode 3|, notwithstanding the presence of the leading edge of the cathode glow on 34 spreading from right to left, except the short gap 33 on cathode 3|. However, in the presence of the leading edge of the spreading glow on 34 combined with ionisation of the gas in any of the gaps between cathode 3| and anode 28 caused by immediately previous firing of an adjacent point on 3|, the voltage at the times of the pulses is; sufiicient to cause the firing of any gap of 3|, or cathode 32. Similarly plate 33 can only be fired by ionisation spreading from the immediately previous firing of 32, together with the presence of the leading edge of the glow spreading from right to left along 34. 34 may not be immedi-t ately above 28 as shown but may be placed in any position which will give the spacing from 28 above described; for instance, it may be placed so that the plane common to 34 and 28, is at right angles to the plane common to 23-45- 32-33 and 28. To achieve the above result a tolerance of about :5% in input pulse amplitude and. of the same order in gap spacings from anode 28, of the points on 3| and cathodes 32 and 33, will in general be sufiicient.

Let the first input pulse now be applied at 44. The gap between point 36 on cathode 34 and anode 28 will fire, and a glow will spread rapidly up the smooth surface of 34 from right to left. During the pulse the leading edge of the glow on 34 will have reached the shorter gap 30, of cathode 3| and 30 will then fire. 32, 33 and all other points than 30, on 3| will not fire, as there is no ionisation of the gas in them from adjacent gaps. On cessation of the pulse at 44 the discharges will extinguish. The next pulse will again fire 34, starting as before at its shorter gap 36. The glow on 34 spreading from right to left will now find that the first point on the line of the points on 3| that is capable of being fired is the gap from point 46 on 3| which is immedi-' ately to the right of 3|l-as this gap is the first, from right to left, in which the gas is sufficiently ionised for the pulse to be able to fire it. The ionisation is due to the recent discharge from point 30 which ionisation will persist between pulses. This gap, 46 will fire before the leading edge of the glow on 34 has reached 36. As soon as 46 fires the voltage drop across the common cathode load 4'! lowers the volts between 46 and 28 to a value sufficient to maintain the discharge from point 46 but insuflicient to fire 30, which remains out. Similarly, the next pulse, after the extinguishing of 46 at the end of the previous pulse, will fire the adjoining gap 48, but no otheras 48 is the first sufficiently ionised gap to be reached by the glow on 34 spreading from right to left.

Successive pulses will similarly fire adjacent points, on 3| one at a time, from left to right, until all points on 3! have been fired. The next pulse will fire only 32and the following pulse only 33. In each case the points of cathode 3| will not re-fire owing to the voltage drop in cathode load 41 on the firing of 32 and 33 respectively.

When 33 fires, 32 cannot re-fire, on account of the charge collected on 36 the action being similar to cathode I in Fig. 1. 33 itself cannot re-fire, because of the charge collected on 46 and all the long gaps between 28 and 3|, are insufficiently ionised. Therefore on the arrival of the pulse following that which fired cathode 33, the shorter gap 36 only will fire again, as soon as the glow on 34 has spread to the left-hand end of 34. The sequence then repeats itself indefinitely. The time-constants of 31-38, and of 3946 are greater than two input pulse time spacings and less than one period of the complete pulse train.

As only one point on cathode 3! can fire at a time, no measures are necessary to stabilize cathode-anode voltage.

If the input pulses are not strong enough alone to fire the cathodes, a battery may be added in series with resistor 29 and ground to assist the pulses. This battery must be insufiicient to maintain any glow in the absence'of an input pulse. This last addition, of course,'slows down the deionising time somewhat, as the anodecathode voltages no longer fall to zero between pulses.

The arrangement of Fig. 2 has the advantages of simplicity low power consumption, rapid operation and long tube life due to the short average time during which each cathode point (except 34) is discharging.

It has thus many of the advantages of the memory eiiect, which is described in another of my copending applications, bearing Serial No. 763,655, filed July 25, 1947.

In Figs. 3, 4 and is shown a device which can be adapted to give the performance of the device illustrated in Fig. 2. A much larger number of gaps can be used with this device.

The dotted line of Fig. 3 encloses a diagram in perspective of the electrodes of a gas discharge tube for use in the device, consisting of a gridlike anode 49 having parallel longitudinal members joined to transverse end members, and a cathode 56, consisting of a wire or strip bent so as to pass to and fro above the anode 49 and having longitudinal members at right angles to the longitudinal members of anode 49, joined at alternate ends by blinds 5!, 52, 53 and 54. Anode 49 and cathode 56 are in parallel planes separated by a distance suitable as the discharge gap of a gas discharge tube.

The end of 53 furthest from the leading-in connection 55 has a thickened portion reducing the gap 56 between it and the adjacent member of 49 to a distance shorter than that between the planes of 49 and the remainder of 56.

At the crossing places between the longitudinal members of cathode 56 and anode 49 there is a series of discharge gaps 56, 51, 58, 59 and 60 along one longitudinal member of 56 and continuing, after bend 5|, with further gaps 6i and 52, and so on till the final gap 63 near the leading out connection 55.

In a plane parallel to those of 49 and 56, is a cathode 64 similar in shape to 56 but preferably having somewhat longer longitudinal members, laterally displaced in relation to those of 59.

Another anode consisting of a flat plate 65 is in a plane parallel to the planes of the other electrodes described above.

The planes of electrodes 49, 50, 64, and 65 in that order, are preferably arranged side by side or one above the other, and spaced apart so as to provide gap distances equivalent to those used in the tube of Fig. 2. For this purpose the gaps between 49 and 56, at the intersections are equivalent to the gaps between 3! and 28 of Fig. 2 and the gaps between 64 and 65 are equivalent to the gaps between 34 and 28 in Fig. 2.

Any other arrangement of the electrodes giving these relative spacings could be used, for instance 49 could be placed below 56, i5 and 18 and not above them as shown in Fig. 3.

At the end of cathode 64 nearest to the leading out connection 66 is a projection 61 pointing towards anode 65, and making a smaller gap at this point, between 64 and 65, than at othe parts of these two electrodes.

Negative pulses, applied to terminal 68 are conveyed to cathode 56 via condenser 69, resistance 16 and lead 55. They are of insufficient amplitude by themselves to cause a discharge between 50 and 49 (the latter being connected to earth via a resistance '1 I The same pulses are also applied to cathode 64 via condenser 12, resistance 13 and lead 66, where they cause a discharge from point 61 to anode plate 65 which rapidly spreads in the form of a glow between cathode 64 and anode 65, following the course of the former from point 6'! towards the other end of 64.

It is arranged that the size of gap 56 is such that the glow between 64 and 65, is sufficient to cause a discharge across this gap in the presence of a pulse together with the leading edge of the glow from cathode 64 when it reaches the vicinity of gap 56.

The circuits constants and tube design are such that the glow between 64 and 65 reaches the end of 64 after about half the pulse duration.

A discharge now takes place across gap 56 and the glow spreads during the remainder of the pulse along cathode 56 in the direction of gap 51 causing ionisation to spread rapidly to that gap.

It might be thought that the gap 14 between the same longitudinal member of 49 and the adjoining longitudinal member 56 would be equally ionised but this is not so owing to the more rapid spread of ionisation when accompanied by the cathode glow, which spreads along a smooth cathode surface whereas the ionisation spread from 56 to 74 must cross an air gap.

On cessation of the pulse the discharge in 56 collapses and the next pulse repeats the process starting with the firing of point 61 to anode 65 and the spread of the glow along 64.

ItIwill be clear" oi course the spreading.

glow along-54: passes near to, the various discharge' gaps at the crossing places between 49j bers of 50, that is to say, where the spread of ionisation is accelerated by the spreading cathode glow along 50 during a discharge. The gap is adjusted however so that the ionisation which can reach a gap across an air space equal to the gap spacing between connective gaps along 49, is insufiicient to cause a discharge. Hence gap 14 will not fire from this second pulse, when the glow from 64 reaches it.

When gap 51 has fired, the glow from 54 will pass on to gap 55 but this gap Cannot fire owing to the voltage drop in the common resistance 10 due to the discharge in gap 51.

The process will be repeated from successive pulses, each pulse firing a further consecutive gap, and gaps firing once only.

When gap 60 is reached, the cathode glow will spread round bend assisted by the proximity of the end longitudinal member of 49, and when the next pulse arrives, gap 6| on the'next longitudinal member of 50, will fire. Gap 6| will receive some ionisation direct, across the air gap between it and gap 60, and will be more ionised than gap 62.

The distance round bend 5|, between gaps 60 and GI may therefore be greater than that between adjacent gaps along one of the longitudinal members of 50, and still permit adequate ionisation of gap 6| for it to fire from the next pulse.

The discharges proceed along the full length of 50 till the last gap 63 is reached. Another cathode 15 is connected to the common resistance via a time constant circuit consisting of resistance 16 and condenser 11. The cathode cor responds to and has the same function as cathode 32 in Fig. 2. It isadjacent to gap 63 and has the same gap distance from a convenient point of anode 49 as the gaps between 49 and 50 (except 56). It is also approximately as far from gap 63 as the lateral spacing between adjacent gaps between 49 and 50.

A further cathode 18 is placed near the cathode I5, being the same gap distance from anode 49 as is cathode l5 and being spaced from cathode by the same distance as that between cathode l5 and gap 63.

Cathode 18 is of the same type and has the same functions as cathode 33, Fig. 2.

Cathodes 15 and 18 are also near enough to cathode 64 to be primed by the glow therefrom when ionised by an adjacent discharge.

When gap 63 has fired and extinguished, a further pulse will fire cathode 15 and yet another will fire cathode 18, as with cathodes 32 and 33 of Fig. 2, being prevented from firing from consecutive pulses by the time constant circuit l6 and IT in the case of 15 and by the time constant circuit consisting of a resistance 19 and a condenser 88, in the case of cathode I8, 63 being prevented-from re-firing from the same pulse as fires 15 and 18 by the voltage drop in common resistance 10.

The counting "tunction of the device is fulfilled by the transformer 8 I, one winding of which is connected between cathode 18 and the-common resistance 10, so that a pulse is developed across the terminals Bland 83 connected to the other winding of 80, every time a discharge takes place from vcathode'l8. v

The positionsof cathodes 15 and 1.8 in Fig. 3 are diagrammatic, there being many possible arrangements for them, including that shown.

The function of the device described in relation to Fig. 3 operates in a similar manner to that of Fig. 2 but permits alarger number of gaps to be provided without unduly elongating thetube.

Figs. 4 and 5 show a plan and elevation of a possible practical construction of the electrodes of the tube illustrated within the dotted line rectangle in Fig. 3, the wires or strips composing cathodes 50 and 64 being supported on insulating pegs 85 attached to anode 65. In Figs. 4 and 5 corresponding elements are indicated by reference numerals corresponding to those in Fig. 3.

Here anode 49 is shown above the other electrodes, and the cathodes l5 and 18 are not shown since the purpose of Figs. 4 and 5 is principally to show the methods of mounting of electrodes 69,50,615 and 65.

It is thus seen that all the devices described in relation to the attached drawings possess the feature of having no battery potential applied to the electrodes between pulses, which is of advantageprincipally in the reduction of the deionising time due to the fall to zero of the anodeto-cathode potential between pulses rather than its reduction to a point above zero. This short deionising time enables the tube to resume sequential firing after a shorter recovery period and therefore enables a higher pulse repetition rate to be used.

The arrangements illustrated in Figs. 2, 3, 4 and 5 have the further advantage of having only one gap discharging at a time which obviates the need for voltage stabilising measures and increases the life of the tube owing to the reduced number of discharges across any gap.

What I claim is:

l. A device responsive to recurring pulses of electrical energy comprising a cold cathode gas discharge tube having a first electrode, a second electrode, said electrodes unevenly spaced from each other to define an extended discharge gap therebetween along which a discharge is adapted to spread upon application of successiv pulses of a series, a plurality of auxiliary electrodes spaced substantially an equal distance from said first electrode and defining an array of sequentially firing auxiliary gaps therebetween, each having an ionization coupling with the extended discharge gap and an adjacent auxiliary gap, one of said auxiliary electrodes having a member defining a smaller gap with said first electrode than the array of auxiliary gaps, said member in proximity with that portion ofsaid first electrode which is spaced farthest from said second electrode, successive of the auxiliary gaps adapted to be fired upon application of successive pulses of aseries.

2. A device as claimed in claim 1 further comprising means for firing alone the sequentially firing gap distant farthest from said smaller gap, means for preventing re-firing of said first mentioned gap until all intervening auxiliary gaps have re-fired and a load circuit coupled to said electrodes responsive to the firing of said first named gap.

3. A device as claimed in claim 2 wherein said f means for firing alone the last of the sequentially firing gaps defined by said electrodes comprises a time-constant circuit in series with the penuIti-L mate of the sequentially firing gaps defined by said electrodes, said circuit having a time-constant greater than the time spacing between recurring pulses applied to said tube.

12 4. A device as claimed in claim 3 wherein said means for preventing re-firing of said last sequentially firing gap until all intervening auxiliary gaps have re-fired comprises atime-constant circuit in series with said last sequentially firing gap, said circuit having a time-constant greater than the time spacing between recurring pulses applied to said tube.

ALEC HARLEY REEVES.

No references cited.

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