US2872620A - Electric discharge tubes - Google Patents

Description

Feb. 3, 1959 A. H. w. BECK ET AL 2,

ELECTRIC DISCHARGE TUBES Filed May 12. 1954 -s Sheets-Sheet 1 fl r 'F/G.

' Inventors A. H W. BECK- M.JACKSON' Attorney Feb. 3, 1959 A. H. w. BECK ETAL' 2,872,620

ELECTRIC DISCHARGE TUBES Filed May 32. 1954 3 Sheets-Sheet 2 36 g i iu Iiwentors A. W. BEC K M. JACKSON- wz www A itorney Feb. 3, 1959 A. H. w. BECK ET AL 2,872,620

ELECTRIC DISCHARGE TUBES 3 Sheets-Sheet 3 Filed May 12. 1954 our o w M. v m km l m .A w J W A y B United States Patent ELECTRIC DISCHARGE TUBES Arnold Hugh William Beck and Thomas Meirion Jackson, London, England, assignors to International Standard Electric Corporation, New York, N. Y.

Application May 12, 1954, Serial No. 429,321

Claims priority, application Great Britain May 19, 1953 Claims. (Cl. s1s-s4.s

' so that when a designated last gap has been fired the next pulse transfers the discharge to a first cathode to recommence the sequence.

The production of such tubes in quantity is complicated by the various circuit uses of tubes having similar characteristics. Thus tubes, otherwise identical, are called for, having, alternatively, ten or twelve cathodes arranged in cyclic sequence. It is inconvenient and uneconomical to produce batches of otherwise similar tubes having different numbers of gaps in the cyclic sequence, and it is an object of the present invention to provide tube constructions and corresponding circuit arrangements in which in a single tube a choice is presented as to the number of discharge gaps which may be included in a cyclic sequence. a

From the circuit aspect the present invention provides a circuit arrangement comprising a gas-filled electric discharge tube having electrodes defining discharge gaps positioned in ionisation coupling relationship in at least two alternative cyclic sequences, circuit connections to the said tube including a common pulse input and an output, means for selecting one of the said sequences, means for applying electric pulses to the said tube and means for maintaining a glow discharge at any discharge gap in the selected sequence whose position corresponds with the number of pulses of a given series of said pulses which have been applied to the tube.

Suitable tubes for use in such a circuit arrangement are modifications, according to the present invention, of tubes such as disclosed in the U. S. Patent No. 2,553,585 of G. H. Hough issued May 22, 1951. The tubes disclosed in that specification are characterised by having two interleaved sets of cathodes, referred to as transfer cathodes and storage cathodes, arranged consecutively in directional ionisation coupling relationship with one another, so that when a voltage pulse is applied in common to all the transfer electrode cathodes, a glow discharge, initially positioned at one storage cathode, is transferred to the next adjacent storage cathode in one direction along the .array of discharge gaps: the succeeding pulses step the discharges along from storage cathode to storage cathode, according to the number of pulses applied, until a final or output storagecathode is reached, after which the glow discharge isv transferred to the first cathode and the sequence may be recommenced.

In the present specification and in the claims the term ionisation coupling is used in a somewhat broad connotation. A gap in ionisation coupling relationship with a discharging gap is fired by reason of the reduction of the striking potential of the primed gap to its main- 2,872,620 Patented Feb. 3, 1959 v "ice taining potential. The reduction of striking potential may be brought about, in part, by the migration of,

charged particles from the priming glow discharge and, to a greater extent, by the illumination of the cathode of the primed gap by the glow of the discharge at the priming gap. In addition, the space charge in the priming gap distorts the electrostatic field within the primed gap and may thereby assist in causing the primed gap to fire. All these effects, therefore, and not merely the migration of ions as such, are to be understood as included in the term ionisation coupling. It should also be stated that in the present specification when a gap is said to be fired it is to be understood that space charge conditions have been set up in the gap to the extent necessary to ensure that discharge is maintained so long as the anode-cathode voltage of the fired gap is at least equal to the maintaining voltage for glow discharge thereat. Similarly, we use the word prime in the sense that if a gap is fully primed it is in a condition to be fired as soon as any hold-off voltage or the like inhibition is removed.

In constructions described in the specification of the aforementioned U. S. Patent No. 2,553,585, directional ionisation coupling is obtained by the special shaping of at least the storage cathodes. The available discharge surface of each of these storage cathodes is divided into two parts: one a main, or plate, portion formed as a rectangular plate parallel to the anode, and the other a tail portion projecting from the plate, the tail portion being in the form of a narrow strip edgewise-on to the anode. Due, principally, to the larger ratio of periphery to surface area of the tail as compared to that of the plate portion of the cathode, the maintaining voltage for discharge over the tail portion is higher than that over the plate portion. The cathode is oriented with the end of the tail portion adjacent the previous gap to fire. When the gap is primed, dischargespreads along the tail and onto the plate portion of the cathode; due to the lower maintaining voltage of the plate portion, the glow discharge then remains on the plate portion while that on the tail portion cannot be maintained. By this means, considering three adjacent discharge gaps, discharge being maintained at the middle one, the ionisation of the gap on one side can be made considerably higher than that to the other, dififerences in the reduction of breakdown voltage of the order of 40 volts being commonly obtained.

Asymmetrical shaping of the cathodes, however, is not the only means of obtaining directional ionisation coupling between adjacent gaps'in a sequence. Alternative arrangements, some involving merely a proper proportioning of the distances between adjacent gaps, and others involving the use of ionisation barriers or light reducing masks or partitions between adjacent gaps are disclosed in U. S. application No. 264,092 of G. H. Hough- T. M. Jackson filed December 29, 1951, now U. S. Patent No. 2,686,273 issued August 10, 1954 and assigned to the same assignee as is the present application.

In the embodiments of the invention at present preferred, and which will be described in detail below, directional cathodes are used, a simplified form of construction, forming the subject-matter of U. S. application No. 421,501, now Patent No. 2,780,747 of T. M. Jackson filed April 7, 1954 and assigned to the same assignee as is the presentapplication, being adopted. In one arrangement to be described, directional cathodes are arranged in a circle and additional ones are positioned in a re-entrant loop so as to be in consecutive ionisation coupling relationship with respective cathodes of the circular array, it being arranged, by means of suitable strapping or the like between cathode connections external to the tube envelope, that a proportion of the cathodes asvaeao ofthe re-entrant loop are included or excluded from the discharge sequence according to choice.

From a constructional aspect, therefore, the present invention provides a cold cathode electric glow discharge tube comprising, within a gas filled envelope and each co-operating with an associated anode to form a discharge gap: a multiplicity of storage cathodes, arranged in a sequence commencing with a first storage cathode, dividing into at least two branches and terminating in a common or a respective storage cathode; a transfer cathode positioned in ionisation coupling relationship between every two consecutive said storage cathodes, including one between the or, respectively, each said output storage cathode and the said first storage cathode; so that, with appropriate circuit connections, a glow discharge initially maintained from any one of the said storage cathodes is transferred from that storage cathode to the next adjacent storage cathode along the said sequence inresponse to a voltage pulse applied in common to all the said. transfer cathodes, successive said pulses stepping the glow discharge along the sequence one storage cathode at a time via one said branch to the output storage cathode and thence to the said first storage cathode and again along the sequence, the said one branch being chosen solely by the choice of connections to cathodes ofthe respective branches.

As stated above, in the preferred embodiment described, at least the storage cathodes are directionally shaped and, in fact, except for one cathode which is provided with more than one tail portion each afiording coupling to a respective different branch or branch loop, both transfer and storage cathodes may be identical in construction. It will be appreciated by those skilled in the art, however, that the present invention is not restricted to the use of tubes having directional cathodes but that other means of obtaining the required directional ionisation coupling relationships between discharge gaps may be used, such as those of the above mentioned U. S. Patent No. 2,686,273.

Various possible alternative arrangements of the invention may be used. For example, a single cathode may be designated or be provided with a separate circuit connection to serve as an output cathode, and connections tothe remaining cathodes may be made so that an alternative number of discharge gaps may be provided in a sequence which terminates at this output gap and recommences at a first gap. Alternatively, the output cathode may be one of those which are contained in the alternative branches, or, again, the invention may be used to provide alternative outputs selected by means of a switch or other means such as an electromagnetic or electronic relay. As mentioned above, in each of the embodiments to be described, one of the cathodes is provided with more than one tail. In some embodiments this plural-tailed cathode is a transfer cathode while in others, at the expense of introducing an additional cathode, the plural-tailed cathode may be a storage cathode, in which case the transfer cathodes can be non-directional, the storage cathodes alone being directional.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Fig. l is a circuit diagram illustrating one embodiment of the invention;

Fig. 2 shows the arrangement of cathodes in a practical construction of tube for use in the circuit of Fig. 1;

Fig. 3 is a perspective drawing of a complete tube embodying the cathode arrangement of Fig. 2;

Fig. 4 shows a circuit diagram of an embodiment adapted to count alternatively ten, eleven or twelve pulses in a cyclic sequence; and

Figs. 5, 6 and 7 show the essential modifications to the arrangements of Figs. 1 and 4 for alternative embodiments of the invention. I

In the circuit diagrams of the accompanying drawings, in order to distinguish their functions, storage cathodes are depicted by larger circles and transfer cathodes by smaller circles, even though in the corresponding practical construction transfer and storage cathodes may be identical. The storage cathodes, or the connections thereto, are numbered 1, 2, 10, 11, 12 or 0, according to the position of the respective cathode in the discharge sequence. Each directional cathode is depicted with a tail bearing an arrow indicating the direction of spread of cathode glow. In all the circuit diagrams the discharge tube 13 is shown'having a common anode 14, and the direction of transfer of discharge along the cathode sequence is shown by the arrow 15, the sequence being shown in straight line formation rather than in the circular formation which the cathodes would occupy'in most practical constructions. Where two or more cathodes are connected in parallel to one another it has generally been more convenient, in the schematic diagrams, to show the connections internally of the tube envelope. It is a matter of constructional and circuit convenience Whether, in, an actual embodiment, such connections are made internally or externally.

In the circuit diagram. of Fig. 1, storage cathodes 1, 2 and 9 are shown connected to earth; the intervening storage cathodes 3, to 8, which are similarly connected, have been omitted to avoid confusing the drawing. Storage cathode 9 is followed, in the sequence of cathodes, by a single transfer cathode 16 which is in ionisation coupling relationship with both storage cathodes 10a and 10b. Cathode Jia shown connected to earth through the normally closed contacts Kb a load resistor 17 which provides an output voltage between the terminal label-led Out and earth. Storage cathodes 10b and 11 are connected together to one of the contacts Ka the other of which is connected to earth. The contacts Ka and Kb are represented as relay contacts; in practice they may be substituted by any convenient connecting means such as appropriate strappings to the tube terminals. When the contacts Ka and Kb are changed over, cathode 10a is disconnected, the load resistor 17 is connected to cathode 12, and the cathodes 10b and 11 are connected to earth. The transfer electrode 18, which is in ionisation coupling relationship with and precedes storage cathode I. has two tails, one of which places it in ionisation coupling relationship with cathode 18a and the other with cathode 12. All the transfer cathodes are connected together to a pulse input terminal 1% and are maintained at the same mean positive potential with respect to earth by a bias circuit consisting of a resistor 20, rectifier 21 and source of bias potential 22 which are connected in series between the H. T. supply and earth. The anode 14 is connected through a common anode resistor 23 to a H. T. source 24, the negative pole of which is earthed. The potential of the source 24 and the value of resistor 23 are chosen so that discharge to any one storage cathode maybe maintained. i i

With the exception of transfer cathode 18, all the cathodes of the tube 13 in Fig. l, are identical, each preferably being formed of a main or head portion indicated by the circles and a tail portion, the head portion in a practical embodiment being a circular disc and the tail portion a wire projecting from it. The cathodes are positioned relative to one another with the head of one cathode and the tail of the preceding one separated by a distance which is equal to the length of the cathode dark space for discharge from the head portion. Assume now that discharge is being maintained from the head portion only of cathode I. A negative pulse is applied to the tcrminal 19 to take the potential of all the transfer cathodes below earth potential. The tail of transfer cathode 25, which follows cathode 1 in the sequence, is much closer to the glow discharge than is any part of the transfer cathode 18 immediately preceding storage cathode 1 since the glow does not spread onto the tail portion of that cathode. As the striking voltage of the gap between 'the tail of cathode 25 and anode I4 is lowered to the maintaining potential by the ionisation couplingjrom the discharge of cathode 1, glow will commence to spread along the tail and thence on to the head portion. Because the head portion of cathode has a lower maintaining potential than its tail portion, discharge at the tail will be extinguished and, for the remainder of the pulse, glow will be confined to the head. The value of the common anode resistor 23 should be such that, when cathode 25 fires, there is a considerable additional voltage drop across this resistor so as to reduce the anode voltage below that necessary for maintenance of the discharge at cathode 1, discharge at the transfer cathode 25 being maintained by the pulse applied to terminal 19. This pu-lse should be of such length that, on its decay, the gap associated with cathode 1 has become de-ionised sufi'iciently to prevent discharge again passing to this cathode.

Instead, the glow spreads along the tail of storage cathode 2 on to the head portion and is there maintained. The next pulse applied to terminal 19 steps the discharge along to storage cathode 3 and successive pulses result in transfer of the discharge from storage cathode to storage cathode, according to the number of pulses which have been applied, up to and including cathode 9.

With the contacts K in the unoperated position indicated, the pulse following that which transferred the discharge to cathode 9 will cause transfer of the discharge via transfer cathode 16 to cathode 10a where it produces an output pulse across resistor 17. The next pulse steps the discharge first to transfer cathode 18, the glow spreading along the tail whose end is adjacent cathode 10a, and thence once more onto cathode 1.

If the contacts K are in the operated position, instead of proceeding to cathode 10a, the discharge will be stepped from storage cathode 9 to storage cathode 10b, and the immediately following pulses will cause transfer to cathodes 11 and 12, which are now in circuit. Thence, the discharge is transferred once more to cathode 1 via transfer cathode 18, the glow spreading this time along that tail of cathode 18 adjacent to cathode 12.

In the preferred practical embodiment of the tube of Fig. 1 the cathodes are made with a disc-shaped portion forming the head and a wire for the tail. The way in which the cathodes may be arranged is shown in Fig. 2, where the cathodes are numbered as in Fig. 1. The storage cathodes 1 to 9, together with the intermediate transfer cathodes, which are physically identical with the storage cathodes, are mounted in the arc of a circle upon an insulator 26. To prevent undesired direct coupling between cathodes 9 and 1 a metal screen 27 is inserted between them. Storage cathodes 10b, 11 and 12, their intermediate transfer cathodes and the transfer cathodes 16 and 18 are mounted in a reentrant loop connecting cathodes 9 and 1. Cathode 10a is positioned, as

shown, partially bridging the loop so that both cathodes 10a and 1012 are in ionisation coupling relationship with transfer cathode 16. The two tails of transfer cathode 18 are arranged with their respective ends one adjacent cathode 12 and the other adjacent cathode 10a.

The cathode assembly of Fig. 2 is mounted in a tube as shown in Fig. 3. The cathode heads are formed on the ends of respective support wires in the same manner as the heads of wire nails. The support wires pass through insulator 26 into tubular shanks 28 to which they are welded. A shoulder integral with the head portion of each cathode raises cathode head and tail slightly above the surface of the insulator 26 so as-to prevent the spread of glow to cathode surfaces underneath the head. The shanks 28 receive, and are welded to, wires 29, which themselves are sealed in a glass base 30 of an envelope 31. An anode 32, in the form of a metal disc with upturned edge, is mounted from additional wires 33 sealed in the glass base 30 and passing through the insulator 26.

By means of the alternative connections to'the cathodes 10a, 19b, 11 and 12, a tube as described with reference to Figs. 1 to 3 can beoperated with repetitive cycles of either ten or twelve pulses and so can be used for counting in a simple decimal or a duodecimal system. By providing appropriate output connections coupled to the various cathodes it can also be used as a dividing mechanism providing an output on receipt of every consecutive 2, 3, 4, 5, 6, 10 or 12 input pulses.

The invention is not limited to two alternative numbers of cathodes in a sequence and, by way of example, Fig. 4 shows a circuit diagram for an embodiment adapted for use with pulse sequences of either 10, 11 or 12 pulses. In this circuit the mechanism of transfer of discharge is exactly the same as in Fig. 1.

With respect to the circuits shown in Figs. 4 through 7, the arrangements are shown schematically. In actual practice the tubes are made either in a circular construction or in any other form of construction in which the distances between gaps, which are coupled to each other by ionisation coupling, are equal. Thus whilst in Fig. 4 gaps 9a and 36 are shown in a substantial distance apart and gap 0 and gap 37 are far apart, yet in the actual construction the distances between these gaps are not greater than that between any other sequential gaps in the tube. Referring again to Fig. 4 the transfer cathode 34 following storage cathode 8 is in ionisation coupling relationship with three succeeding storage. cathodes 9a, 9b and 9c. The connection to cathode 9a is shown taken out separately to a contact on a switch 35, which is shown in the position marked X, connecting the cathode to earth. Cathodes 9b and 10b, with their intermediate transfer cathodes, form a second branch to the cathode sequence and both these two storage cathodes are connected to the switch contacts marked X1. A third branch is formed by storage cathodes 90, 10c and 11, together with a pair of intermediate transfer cathodes. The storage cathodes of this third branch are connected to the contact on switch 35 marked X11. Besides having three branches, the tube 13 and the circuit of Fig. 4 is differentiated from Fig. 1 in that a single output cathode, labelled 0, is providedfthe preceding transfer electrode 36 has three cathode tails, whose ends, as indicated by the dotted lines, are respectively adjacent storage cathodes 9a, 10b and 11. The transfer cathode 37, intermediate storage cathodes 0 and 1, has only one tail, adjacent cathode 0.

In Fig. 4 it will be seen that, with the wiper of switch 35 in the position X as shown, discharge proceeds from cathode 1 along the sequence of cathodes until it reaches storage cathode 8, after which it is transferred via transfer cathode 34 to cathode 9a and thence, via transfer cathode 36, to the output cathode 0 and so back again, via transfer cathode 37, to cathode 1. A count of ten is thus available. With the wiper of switch 35 in position X1, cathode 9a is disconnected and cathodes 9b and 10b are connected to earth. Discharge now proceeds from transfer cathodes 34 along the second branch of the sequence to transfer cathode 36 and again to the same output cathode 0, the connection providing for a count of eleven. Similarly, with the wiper in the third position X11, discharge proceeds along the branch of cathodes 90, 10c and 11 so providing a count of twelve.

In the discharge tubes 13 of Figs. 1 and 4, in order to transfer the discharge sequence from the branch loops back again to the main array of cathodes, an intermediate transfer cathode is required having more than one tail. In Fig. 5, in which only that part of the tube and circuit with which we are immediately concerned is shown, there are two branches, namely the cathodes 9a, 10 and 11 and the cathode 912, both feeding a common output cathode 6 and commencing from a single transfer cathode .34, as in Fig. 4. In similar manner to the arrangement of Fig. 4, in Fig. 5 the switch 38 connects either cathode 9b or the cathodes 9a, 10 and 11 to earth.

In place, however, of the plural-tailed transfer cathode 18 of Fig. l, or 36 of Fig. 4, all the transfer cathodes 2s- 931 e a ut a oubl a s r d an h output cathode 0.' A separate transfer cathode 39 is placed between cathodes 11 and and a transfer cathode 40 between storage cathode 9b and the output cathode 0. Compared with a two branch version of the circuit of Fig. 4, providing the same circuit facilities, the arrangement of Fig. 5 entails a tube having one extra cathode. On the other hand, whereas in Figs. 1 and 4 both. transfer and storage cathodes had to be directional, the arrangement of Fig. 5, using a plural-tailed storage cathode inside of a plural-tailed transfer cathode, makes it possible, if desired, to dispense with the directional features of the transfer cathode, using suitable circuit modification such as will be described with reference to Fig. 6.

In the arrangement of Fig. 6 only the storage cathodes are. directional. Two branches of cathode sequence are shown, involving cathodes 9a and 10a and 9b and 10b respectively. Each storage cathode is provided with a resistance-capacity delay circuit, storage cathode 8 is connected to earth through resistance-capacity delay circuit 41. Cathodes 9a and 9b are both positioned in ionisation coupling relationship with the non-directional transfer cathode 42, succeeding cathode 8, and one or other of this pair of storage cathodes is connected to earth through the switch 43 and the delay circuit 44. Cathode 10a is connected to ground through delay circuit 45 and. is also connected through a D. C. blocking capacitor 46 to an output terminal 47 labelled Out 1. Similarly cathode 10b is connected to earth through delay. circuit 48 and also via D. C. blocking capacitor 49 to terminal 50 labelled Out 2. Storage cathode 1 is shown dotted to the right of cathodes 10a and 10b, discharge being transferred thereto from either 19a or 101) via transfer cathode 51, which, together with its circuit connection, is also shown dotted. The manner in which a discharge may he stepped along from storage cathode to storage cathode. using non-directional transfer cathodes is very fully discussed in the specification of the aforementioned U. S. Patent No. 2,686,273, but that for one mode, of operation will be briefly recapitulated here.

Consider discharge to be maintained at cathode 8 with the switch 43 in the position shown, so that cathode 9a is in circuit. Transfer cathode 42 is closely adiacent cathode 8, so that when a pulse is applied to all the transfer cathodes, cathode 42 is fired in preference to any of the others, as it is in closest ionisation coupling relationship with cathode 8. The common anode resistance, not shown in Fig. 6, is of such value that the additional voltage drop across it reduces the voltage applied to the gap between anode 14 and. cathode 8 below the maintainingp otential, it being remembered that cathode 3 is positive with respect. to earth because of the voltage drop across the resistor in the delay circuit 4 Discharge at cathode 8 is therefore extinguished and the potential of this cathode remains above earth for some little time due to the action of delay circuit 41. Cathode 9a, however, is at earth potential and so, on passage of the transfer pulse, discharge spreads along the tail of cathode 9a rather than re-establishing itself at cathode 8. The discharge spreads to' the head of cathode 9a, as described above in conection with Fig. 1, and is there maintained until the arrival of the next transfer pulse, which steps the discharge along to cathode 10a and produces an output pulse at terminal 47. With the switch &3 in the other position, cathode 9a is disconnected and, in place, cathode 9b. is connected to the delay circuit 44. In this case, starting from cathode 8, discharge is stepped to transfer cathode, 42, as before, but then moves to cathode 911, from whence it is transferred to cathode 10b. producing an output at terminal 50. In either scquence the input pulse following transfer of discharge to the respcctive, output cathode steps the glow back again to. cathode. 1.

electrodes are connected in parallel and choice between the branches of the discharge sequence is effected by alternative connections to storage cathodes. In Fig. 7 We show an arrangement in which all the storage cathodes are permanently connected, the said choice being made by alternative connections to transfer cathodes. in Fig. 7, therefore, an output cathode 0 is connected to ground through resistor 17 across which an output voltage may be derived between the terminal labelled Out and earth. The remaining storage cathodes are connected directly to earth. The transfer electrodes respectively intermediate cathodes (3, 1 9, ending with the transfer cathode 52, are all connected to an input circuit as shown in Figs. 1 and 4. A switch 53 makes contact alternatively between transfer cathode 52 and transfer cathodes 54 or between transfer cathode 52 and each of transfer cathodes, 55, 56 and 57. Transfer cathodes 54 and 55 are both positioned in ionisation coupling relationship with storage cathode 9 and the output cathode 9 is similarly in ionisation coupling relationship with both transfer cathodes 54 and 57. Hence, in similar manner to that described in connection with Fig. 5, a discharge sequence proceeds either form cathode 9 directly to cathode ll, giving a count of 10, or to cathode J via cathodes 16} and 11, giving a count of 12.

Although in Fig. 7 all cathodes have been shown as being directional, it will be evident that, with the storage cathode 0 provided with two tails, non-directional transfer cathodes can be used if delay circuits are inserted in the leads to the storage cathodes in similar manner to that described in connection with Fig. 6.

While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What we claim is:

l. A circuit arrangement comprising a cold cathode gus filled electric discharge tube having electrodes defining discharge gaps positioned in ionisation coupling relationship in a plurality of cyclic sequences containing different numbers of gaps, circuit connections to said tube including a pulse input common to all of said gaps, means for selecting one of said sequences, means for applying a given series of successive electric pulses to said common pulse input to cause sequential discharge of said gaps, means for maintaining a glow discharge at any discharge gap in the selected sequence whose position corresponds with the number of pulses of said given series which hnvc been applied to said gaps, whereby the tube may be operated in cyclic manner with respect to series containing respective different total numbers of pulses, and means for deriving output from said tube.

2. A cold cathode electric glow discharge tube comprising, within a gas-filled envelope, 9. common anode and each co-operating with said anode to form a discharge gap: a multiplicity of storage cathodes arranged in a sequence commencing with a first storage cathode, dividing into at least two branches and terminating in a respective storage cathode, a transfer cathode posi tioned in ionisation coupling relationship between every two consecutive said storage cathodes, including each said output storage cathode and the said first storage cathode; a common connection among said transfer cathodes so that, with appropriate circuit connections, a glow discharge initially maintained from any one of the said storage cathodes is transferred from that storage cathode to the next adjacent storage cathode along the said scqnence in response to a voltage pulse applied. to said common connection to all the said transfer cathodes, successive said pulses stepping the glow discharge along the sequence one storage cathode at a time via one said branch to. the output storage cathode and thence to the said first storage cathode and again along the sequence,

the said one branch being chosen solely by the choice of connections to cathodes of the respective branches.

3. A cold cathode electric glow discharge tube comprising, within a gas-filled envelope a plurality of cathodes, a common anode cooperating With said cathodes alternate of said cathodes designated as storage and transfer cathodes, a common connection among said transfer cathodes, all of said cathodes arranged along 'a closed path so that a numbeig n, of successive voltage pulses applied to said common connection cause a discharge initially maintained at the kth of said storage cathodes, thereby transferred by means of ionisation coupling to the (n+k)th storage cathode around said path, said path including a branch loop, the cathode at the junction of said loopbeing in ionisation coupling 7 relationship with the cathodes adjacent thereto in each branch of the loop, means for directing the discharge to either branch of said loop, whereby by choice of connections to said adjacent cathodes certain cathodes of the loop selectively take part in and certain other cathodes of the loop are excluded from the sequential discharge around said path.

4. A tube according to claim 2 in which, at the commencement of a said branch the first storage cathode of each said branch is arranged in ionisation coupling relationship with the same preceding transfer cathode.

5 A tube according to claim 4 in which a single transfer cathode is arranged in ionisation coupling relationship with the first storage cathode of each said branch and the said first cathode of the said closed path.

6. A tube according to claim 4 in which the said branch terminates in a common storage cathode arranged in ionisation coupling relationship with the last transfer cathode of each said branch.

7. A tube according to claim 6 in which the storage cathodes are directional and the transfer cathodes nondirectional.

8. A tube according to claim 6 in which all transfer cathodes are connected in circuit and the alternative connections to the branch or branch loop, respectively, are made by alternative connections to storage cathodes.

9. A tube according to claim 6 in which all storage cathodes are connected in circuit and alternative connections are provided to transfer cathodes.

10. A cold cathode gas-filled electric glow discharge tube comprising: an odd number of similar cathodes positioned consecutively in unidirectional ionisation coupling relationship one with the next along a portion of a path which is closed by a further re-entrant path portion; further similar said cathodes positioned in the same said cyclic unidirectional ionisation coupling relationship along the said re-entrant path portion, the first and last of these further cathodes being positioned, respectively, in ionisation coupling relationship with the last and the first cathode in the other portion of the said path; and a separate intermediate cathode positioned between the first and the last cathode in the said re-entrant portion, and in ionisation coupling relationship with the first cathode of the said re-entrant portion; the last cathode of the said re-entrant portion having two tail portions for providing ionisation coupling relationship between it and the said separate intermediate cathode and the penultimate cathode of said re-entrant portion, respectively; an anode associated with each cathode; and a common connection among alternate of said cathodes, said connection adapted to be coupled to a source of successive voltage pulses, whereby the glow discharge from cathode to cathode is transferred along the said path upon the receipt of each pulse, alternatively ineluding all the cathodes of the said re-entrant portion except the said intermediate cathode, or proceeding via the said intermediate cathode, omitting the remainder of the cathodes in the said re-entrant portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,524,213 Wales Oct. 3, 1950 2,553,585 Hough May 22, 1951 2,598,677 Depp June 3, 1952 2,603,765 Reeves July 15, 1952 2,675,504 Wales Apr. 13, 1954 2,770,417 Gloess Nov. 13, 1956

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