US2091439A - Multipactor oscillator and amplifier - Google Patents

Description

'Aug. 31, 1 937. P; T. FARNSWORTH IUL'I'IPAC TOR OSCILLATOR AND AMPLIFIER Filed Feb. 24, 1936 2 Sheets-Shoat 1 I U I INVENTOR,

PHILQ 1: mmvswon TH.

- Aug.3l, 1937. P. T. FARNSWORTH 2,091,439 IUL'I'IPACTOR OSCILLATOR AND AMPLIFIER Filed Feb; 24, 1936 f 2 Sheets-Shoot 2 IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII INVEN'IOR, PHILO- 1: rAR/vswoRrM ATTORNEYS.

' Patented Aug. 31,. 1937 "2 091,439

amass m'ri'rsc'ron oscm'ron AND smu Phiio '1'. San Francisco, Calif., as-

, I slgnor to Farnsworth'lclevision Incorporated, San Erancisco, Calif., a corporation of California' f Application February 24,1936, Serial No. 65,465 in Claims. (c1. zso- -zn My invention relates to a multipactor oscillator and amplifier, and more particularly to a means and method of utilizing secondary emission for the production of electron multiplica- 55 Figure 1 is a diagrammatic sectional view, to-

gether with a multiplier circuit, of a preferred form embodying my invention.

Flgureii is a sectional view and circuit diagram embodying the tube'shown-inl lgure 1, connected The impressed It. I". initiates, by the multiphtionp tobe a self-oscillator. 6

This device operates broadly on the principles Figure 3 is a" view, partly in section and partly "set forth in my prior application, Serial No. 692,- in elevation, of a multlpactor structure utilizing 1585, filed October '1, 1933, for an Electron multifour electrodes dmcribing a cylinder around the plying device", and my prior application, Serial central anode.

No. 106,965, flied January 17, 1934, for fMethods Figure 4 is a sectional view taken as indicated 10 of electron multiplication". by the line 4-4 in Figure 3, together with an op- The present application deals with a multieratingcircuit attached thereto.

pactor structure and method of operation where The operation 0! my electron multiplier or multiplication and collection are separated. The multipactor, as I desire to call my device, depresent device is, in common with the previous pends upon the transference of energy between types of multlpactors described by me, capable an oscillating cloud of electrons" and an'oscillatof producing amplification by electron muitipli ing E. M. I"., usually established between apair cation, and by proper connection can be made of opposed cathodes, treated or otherwise cato generate self-sustaining oscillations. pabie of producing secondary electrons at a re.-

The primary object of this invention is to protio greater than unity when impacted by the oso vide an improved means and method of abstractcillating electron cloud. If the energy transfer ing power from a multipactor. be from the oscillating E. M. 1". to the electron Other objects of my invention are: To procloud. the electrons strike the cathodes and give vide an oscillator which will convert direct cur- '-rise to the secondary electron multiplication pherent energy at extremely high enlciency; to pronomena. If, on the other hand, energy is abvide an oscillator or the high vacuum type which sorbedfrom the oscillating cloud of electrons, the. is not subject to the instability and inconsisoscillating fleldbetween the cathodesis intensitencies which such phenomena inti'iz duce; to profled. and the tube may sustain oscillations in the vide an oscillator and amplifier whichhas no cathode circuit. i heated electrode of the thermionic type, and I .Thejpresent invention concernsa device where so 'which is correspondingly free of the difiiculties both of these phenomena are produced in diiIerand complications introduced by cathode heating but adjacent structures, electrons being ing surfaces; to provide an electron multiplier passed, preferably through a common cathode, structure which is capable of generating. selffrom one tothe other. v 5 sustained oscillations and which may be readily Considering then, first, the condition where modulated; to provide a means and method of energy is transferred from the applied E. M2. 1'. operating a combined multipactor and output to the electron cloud. I find that when the period structure having a common cathode;'to provide of the oscillating cloud of electrons is close to a ineansand'method of creating, an oscillating the resonant frequency of a circuit connecting 4o cloud, of electrons, and a means and method of the cathodes, that-the tubeacts as a highly efa absorbing power from this cloud; and to provide flcient electron multiplier and. in many cases.

asimple andeflicient multipactor tube. will self-oscillate if energy is withdrawn from. My invention possesses numerous other'objects the multipactor structure and used, at least in and features of advantage, some'of which, to-' part.'to supply the oscillating I. M. I". applied gether. with the foregoing, will be set forth in to the cathodes, energy in this caserof course, 45 the following description of specific apparatus being supplied from a D. C. source applied to embodying and utilizing my novel method. It an anode preferabLv positioned betweenthe two is therefore to .be understood that my method is cathodes. 1 applicable-to other apparatus, and-that I do not When the period of the oscillating. cloud of to limit myself; in any way. to the apparatus of the electrons is close-to th res na t freq y of so present application. as I- may adopt various other the circuit connecting the cathodes, it is found, apparatus embodiments,' utilizing the method, experimentally. that the tube generates oscilwithin the scope ofthe appended claims. lations which are largely determined by the res- Referring to thedrawings; onantfrequency of the tuned circuit.

cation process, a cloud of electrons of the proper phase to absorb energy from the oscillations.

This cloud of electrons would oscillate by itself at approximately the same frequency as that of 5 the circuit, except for the fact that the R. F. itself accelerates the cloud and makes the trip across the tube less than a half period of the tuned circuit. The mere fact that the electrons are. speeded up insures that they strike the oathode. The returning group of electrons also make the trip in slightly less than one-half cycle. The result is that the fastest electrons very rapidly get out of phase with the potential. The electron distribution in the cloud, however, reshapes itself at each half period because the rate of multiplication is large compared to the 'amount of phase shift.

The process results, however, in electrons being fed from the multiplication phase into the opposite phase wherein an electron is decelerated rather than accelerated by the R. F. Electrons in this phase do not strike the cathodes at all, but continue to oscillate between them, delivering energy to the external circuit as they are slowed down by the R. F. If the probability of an electron striking the anode is suffioiently small, equilibrium current results when the electrons are fed from the multiplying phase into the energy-giving phase at the same rate as the electrons are multiplied at the cathode, and electrons of the energy-giving phase never strike the cathode until they have given substantially all their energy to the oscillating circuit. a I may desire, however, as in the present case, not to abstract power directly from the multipactor structure, but to utilize directly a portion of the oscillating cloud of electrons in another structure closely associated with the first, and

very emcient secondary emissive surface, with ratios as high as one primary to six secondaries, when impacted at the proper velocity, but I do not wish to be limited to such'a formed surface as even untreated nickel has been found to have an emission ratio greater than unity; and any surface, formed or unformed, having such a ratio will be satisfactory, although, of course, multiplication can be accomplished with alesser number of impacts with the materials having'higher Collector cathode 9 is supported on a lead II passing through a seal I 2 in the end of the tube.

.collector cathode 9, however, differs from multiplier cathode 2 in that its inner surface is preferably of a nature that it will not emit second- I aries, at least secondary emission will be-reduced to a minimum;- and I have found that a carbonized nickel surface in this position will-prevent, to a large extent, secondary emission.

After the electrodes have been assembled as described, the tube is, of course, baked out. de-

withdraw the multiplied output from the second 40 structure.' My invention may be more fully understood by direct reference to the drawings, which show an improved type of multiplier structure connected,

in Figure l, as a direct electron multiplier.

The tube itself comprisesa conventional type of multipactor, as hitherto described and claimed by me in the applications referred to above, com-- structure.

The cup-shaped cathode 2- may be mounted in any convenient manner, such as on a lead 3 passing through a reentrant stem 4 in the end of the tube.

The opposing cathode may conveniently be located at approximately the midpoint of the tube,

and comprises ascreen cathode l5 extending across 50 the tube and preferably positioned within a cathode cylinder 6.

Between the two cathodes is positioned a multiplier anode l preferably in the form of a cylinder whose walls are-in the same projected surface as determined by the. walls of the cup 2 and the cylinder 8. The ,interior of the cathode cup 2 and the surface of the cathode screen- 5 are preferably sensitized so that they will emit secondaries at a ratio greater than unity, when impacted, and this sensitization, which is performed in order that the highestpossible ratio may be obtained, may be accomplished by forming the cathodes of silver, oxidizing the silver, and depositing caesium thereon, for example. Such a surface makes a nections.

'gether through separate radio frequency chokes gassed, evacuated, and the surfaces formed on cathodes 2 and 5.

For multiplication, the tube isconnected as shown in Figure 1. On the multiplier end radio frequency is fed into the input connection ll through a blocking condenser II, to cathode 2 through lead 3, and cathode 2 is connected through a tunable resonant circuit II to the screen cathode. 5 through suitable ground con- Anodes I and ID are connected tol'l to a D. C. anode source l8, the opposite end of which is also grounded, the positive end of this source being connected to the anodes.

The collector cathode 9 is connected through an output resonant circuit'2ll to ground, and the output may be taken from this cathode through blocking condenser 2|. All that is necessary to 'set the tube into oscillation is to energize the anodes land ID, as there will be, in the space between cathodes 2and 5, a suiiicient number of free electrons which are accelerated toward one or both of the cathodes by the potential of -the anode, to strike thereon and cause the initiation of secondary emission.

If, then, a radio frequency is applied between the cathodes 2 and 5 and controlled by means of the tuned circuit l8, and the time of flight of the electrons between cathodes 2 and I is adjusted by means ,of placing upon the anode I the proper potential so that the time of flight corresponds to the period of the input, oscillations of the electrons'between the two cathodes will occur and repeatedimpacts with the oathodes will take place with the release of secondary electrons at each impact.

Inasmuch as the field between the cathodes is so arranged either by the construction of the cathodes,.-as shown, or by an extemal' electric field, as has been pointed out in my Prior cited applications, certain definite members of traversals will take place before collection by anode l from previous multipactor -1 1- ha e, and therefore are 70 mon 'tune'd circuit occurs, and a d te multiplication factor will be reached before equilibrium current is arrived at in the tube. Thus, there will occur within the multiplier end of the tube, electron inuitiplica-' 5 tion: and I prefer, with this type of tube, to soadiust the constants on thctwo cathodes'and the anode of the multiplier structure, that a maximum equilibrium current is reached.

The structure just described, however, diiiers structures in that the central cathode K is apertured. This means that at each time the electron cloud reaches the plane of cathode I, acertain number of electrons impact and create secondaries which are -.used to continue the'multiplication process, but others oi the electrons pass directly through-the ape'r-. ture in cathode l and enter the output structure comprising cathode I, anode Ill and cathode I. r In this structure, however, conditions aredii- 2 1mm. The output cathode O has been treated to prevent secondary emission, and ii cathode I is connected to cathode 5 through a tuned circult 2", the electrons passing through the cen- -tral cathode 5 will tween cathodes 9 and 5, and energy will be absorbed from them as they oscillate between cathodes O and I: in other words, in the output structure, energy is being absorbed from the electrons. 1

The advantage gained in taking energy out of thetube in this manner is that phase shift of the oscillating-electrons ln-the output structure is unimportant. In other words, any electrons in the output portion of the tube which get out in a positionto absorb energyirom the oscillations, strike the oathodes and are absorbed by them, and as the potentialon the anodes in each portion oi! the tube can be adjustedso that the electron oscillation frequency coincides with that of the tuned circuits and with, the E. M. 1". to be amplified, both structures operate completely in phase.

It will be understood, of course, that'the output structure does, in no sense, 4'5 multiplication;

' sorbs all electrons striking it, and will not release secondaries. In other words, by using symmetri-j cal structure operating in phase, I have separated multiplication and output. I create the oscillation of the electron cloud and'supply power to it, in one structure, withmultiplication; and I absorb power from the cloud, without multiplication. in the other structure. I

I'have thus eliminated thenecessity within the multiplier structure of developing a largeout-of-phase component, in order that power he absorbed from the cloud. In other words, it is necessary, as above explained, in order to create 00 an output from the ordinary multiplier, to absorb power from which is' out of phase with the multiplying cloud. In this case only enough power is absorbed to continue multiplication. 5 Such an arrangement leads to a high conver- ,sion'emciency, and also leads to a high efliciency sell-oscillator. For example, I have shown a circult in Figure 2 where the output cathode 9 is coupled to the input cathode 2 through a com- 22, an intermediate tap 24 bei taken from the inductance of the tuned circuit to the central. apertured cathode 5. Such a connection causes self-oscillation of the multiers'tructure comprising cathodes 2 and t and 7 anode-I, with additional power being absorbed in fures 3 and ,4. In

' cathode, however,

oscillate back and term he to become a sell-oscillatory create electron it is in eflect a multiplier strue- 'ture with the exception that the cathode 9 aba component of the electron.cloudthe" I together with anode II. This power is fed back to the input structure, and thus the E. M. Eds regeneratively amplified and an extremely ei fi cient oscillator results.

- 'Another structural embodiment utilizing 'my method of electron collection is shown in Fig- I this tube, opposed multiplying cathodes 2t and 2| are connected through the tunable resonant circuit 16. Cathodes-25 and 26 are sensitized. as were cathodes 2 andlior secondary'emission, and is at central spiral 21..

Output cathodes 2i and 2e are also positioned in opposed relation, the and 2! being positioned to form a cylinder, each being electrically separated, and output cathodes 28 and" are also connected in this case. the anode by tunable resonant circuit 20'. Output cathodesdo not emit secondaries and may be of carbonized nickel, as explained above for output cathode 9. The anode 21 is supplied with tial from the anode battery I9.

I also prefer to provide, preferably by means of a focusing coil ll energized by focusing source 3| underthe control ofa resistor 32, a feeble magnetic field in the tube with the lines of force axial, so that there will be a progression of the electron oscillation paths in the direction from multiplier cathodes to output cathodes. For example, when radio frequency is applied between the multiplier cathodes '25 and 28, either from a driver or by causing the two vmultiplying cathodes structure, the electrons oi the proper phase for multiplication tend to oscillate so that they are traveling along the center line connecting the multiplying cathodes,

and the electrons oscillating in the phase .to give. up their energy to the output circuit 20 tend to swingaround at right angles to the multiplier cathodes. The application of the magnetic field effectively prevents the output electrons from swinging around, so that they are absorbing power. There is therefore, due to'this field, a continuous drift of multiplying electrons over to the output cathodes 28 and 29, where they are collected'aitergiving up their energy to the output circuit. f

The main advantage of this type oi structure over ,the structure heretofore described is that four cathodes 25,16, 28"

structure comprising cathodes Iv and a positive potenall of the; current built up by.multiplication is eventually converted into oscillating power, resulting in ,a very high emciency.

Other circuits utilizing the means and method herein described will. readily suggestthemselves to those skilled in the art, the circuits shoWnbeing in the nature of examples only.

.Iclaim:

1. An electron multiplier comprising a pair of opposed surfaces capable of emitting secondary electrons at a ratio greater than unity when impacted, means for causing an oscillate between said surfaces-to create repeated multiplying impacts therewith, means for divertinto a spaceapart from that bounded by said .suriaces, and means ing a portion of said cloud .ior absorbing power from said diverted portion withlnsaid space. g

2. An electron multiplier comprising a' pair of opposed surfaces capable of emitting secondary electrons at a ratio greater than unity when impacted, means forcausing an electron cloud to oscillate between said surfaces to create repeated multiplying impacts therewith, one of said sur- -faces being apertured to allow'a portion of said thus electron "cloud to;

r portions from the space bounded by said surfaces,

cloud to pass therethrough at the time of each impact, and means for absorbing power from the electronspassing through said apertures.

3. Anelectron multiplier comprising a pair of opposed surfaces capable of emitting secondary electrons at a ratio greater than unity when impacted, means for causing an electron cloud to oscillate between said surfaces to createrepeated multiplying impacts therewith, means for dividing said cloud at the plane of one of said sur- Y faces, means for abstracting one of the divided portions from the space bounded by said surfaces, and means for absorbing power from the obtained.

abstracted portion.

4. An electron multiplier comprising a pair of opposed surfaces capable of emitting secondary electrons at-a ratio greater than unity when impacted, means for causing an electron cloud to oscillate between said surfaces to create repeated multiplying impacts therewith, means for dividing said cloud at the plane of one of said surfaces means for abstractingone of the divided portions from the space bounded by said surfaces, means for absorbing power from the abstracted portion, and a work circuit for utilizing the power 5. An electron multiplier comprising a pair of opposed surfaces capable of emitting secondary electrons at a ratio greater than unity when impacted, means for causing an electron cloud to oscillate between said surfaces to create repeated multiplying impacts therewith, means for dividing said cloud at the plane of one of said surfaces, means for abstracting one of the divided means-for absorbing power from the abstracted portion, a work circuit for utilizingthe power obtained, and means for feeding energy from said work circuit into said oscillating cloud.

6-. An electron multiplier comprising a pair of opposed surfaces capable of emitting secondary electrons at a ratio greater than unity when impacted, means for causing an electron cloud to oscillate between said surfaces to create repeated multiplying impacts therewith, means for dividing said cloud at the plane of one of said surfaces, means for abstracting one of the divided portions I from the space bounded by said surfaces, means and means for utilizing a portion of the energy' for absorbing power from the abstracted portion,

a work circuit for utilizing the power obtained.

, in said work circuit to cause continued oscillation 'of said cloud.

7. 'An electron multiplier comprising a pair of opposed surfaces capable ofemitting secondary electrons at a ratio greater than unity when impacted, means for causing an electron cloud to oscillate between said surfaces to create repeated multiplying impacts therewith, means for dividing said cloud at the plane of one of said surfaces,

- means for abstracting one of the divided portions for absorbing power from the abstracted portion,

from the space bounded by said surfaces, means a work circuit for utilizing the power obtained,

and means for feeding back a portion of the energy in said work circuit into said oscillatingcloud in the proper phase to continue the oscillation thereof.

-8. In an electron multiplier wherein electrons are directed against a cathode surface to produce secondary emission therefrom, the methodof power-production comprising oscillating elec-.

,set of paths, and

from the cloud through apertures in said surface a definite proportion of the electrons therein, and

absorbing the energy from the abstracted electrons. I

, 9. In an electron multiplier structure wherein an electron cloud is oscillated against and away from a surface to produce secondary emission therefrom upon impact therewith, the method of abstracting power from said cloud which comprises feeding energy to said cloud and abstracting energy from said cloud within different spatial boundaries.

10. In an electron multiplier structure wherein an electron cloud-is oscillated against and away from a surface to produce secondary emis- 'sion therefrom upon impact therewith, the meth 0d of, abstracting power from said cloud which comprises dividing said cloud at each impact feeding energy to one portion of said cloud to continue multiplication and abstracting useful energy from'the other portion.

11. In an electron multiplier structure wherein an electron cloud is oscillated against and away from a surface to produce secondary emission therefrom upon impact therewith, the method of abstracting power from said cloud which comprises absorbing energy from said cloud, using' said energy to sustain oscillation of said cloud until an equilibrium current is reached, abstractingelectrons from said cloud, absorbing energy from said abstracted electrons, and adding said energy to that previously absorbed from said cloud to create regenerative oscillation thereof.

12. In an electron multiplier structure wherein an electron cloud is oscillated againstand away from a surface to produce secondary'emission therefrom upon impact therewith,- the method of abstracting power from said cloud I which comprises feeding energy to electrons traveling along one set of paths, changing the paths,- and abstracting power fromsaid electrons while in said changed paths.

' 13. In an electron multiplier structure wherein an electron cloud is oscillated against and away from a surface to produce secondary emis-' sion therefrom upon impact therewith, the method of abstracting power from said. cloud which comprises feeding energy to electrons traveling along a diametrical path, shifting the' electrons to. a different diametrical path, and absorbing power different path.

' 14. In an electron multiplier structure wherein an electron cloud is oscillated against and away from a surface to produce secondary-emission therefrom upon impact therewith, the method of abstracting power from said cloud 'whioh comprises feeding energy to electrons traveling along one set of paths, continuously diverting a portion of said cloud into a different absorbing. energy from said electrons while in saiddifl'erent paths.

15. In an .electron multiplier structure where- .in an electron cloud-is oscillated against and away from a surface to produce' secondary emission therefrom upon impact therewith, the method. of abstracting power from said cloud which comprises feeding energy to said cloud to from said eledtrons while in said 'maintain oscillation of the cloud across a space in a predetermined path, shifting the oscillation to a different predetermined path, and absorbing power from the electrons in the latter path.

16.- In combination, a pair of opposed electrodes capable of emitting secondary electrons at 'a ratio greater than unity, a second pair of op- I 9,091,439 5 posed electrodes inca able of emitting secondary cousins le tr n oscillati n between said first electrons. adjacent saidfirst pair, means for pair of electrodes to cause secondary emission feeding energy to electrons in the space between therefrom, means for rotating the oscillation said first pair oi electrodes to produce electron path around the axis of said cylinder, and means 5 multiplication by cyclical impact therewith, and associated with said second pair of electrodes 5 means associated with said second pair of elecfor absorbing power from electrons in said rotrodes for absorbing power from said electrons. tated path. 1

17. Incombinatiomapair oi opposedelectrodes a 19. In combination, a pair of opposed eleccapable of emitting secondary electrons at-a trodes capable of emitting'secondary electrons. lo ratio greater than unity, a second pair of opat a ratio greater than unity, a second pair of 10 posed electrodes incapable of emitting secondary opposed electrodes incapable of emitting secondelectrons, said pairs being alternately disposed ary electrons, said pairs being alternately disto describe a symmetrical space, means for ieedposed to describe a cylindrical space, means for ing energy to electrons in the space between said causing electron oscillation between said first pair 15 first pair 01' electrodes to produce electron muloi electrodes to cause secondary emission there- 15 tiplication by cyclical impact therewith, and from, means for rotating the oscillation path means associated with second pairof electrodes around the axis oi said cylinder, means associfor absorbing power from said electrons. ated with said second pair oi electrodes for ab- 18. In combination, a pair of opposed elecsorbing power from electrons in said rotated 20 trodes capable of emitting secondary electrons path. and means for collecting electrons contact- 20 .at a ratio greater than unity, a second pair of ing said'second pair of electrodes due to said opposed electrodes incapable of emitting secondrotation. ary electrons, said pairs being alternately dis- PHILO T. FARNSWORTH. posed to describe a cylindrical space, means for v GERTIFICATEOF comancrror. Patent No. 2,o91,l 9, August 1951 v 91111.0 1'. FARNSWORTHI.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 71;, forthe word "members" read numbers; and that the said Letters Patent shonldbe read with this correction therein that the samemay conform to the recorder the case in the Patent Office..

Signed and sealed this 1 th day of October, A. D. ;l958.

Henry Van Arsdale- (Seal) I Acting Commissioner of Patents.

DISCLRIMER f 2,091,439.-Philo T. Fm San Francisco Calif Mon'rr ANn'AMPmrmn; Ifate'nt dated A st 3l l937. DisJ3:fez- 512a 31 s;31 2:1

R 5b, 1942, by the assig nee, Famswo Television & Radio Corporation.

specifigteioienters this disclaimer to claims 1, 3, 4, 8, 9, 10, 12, 14, 15, and 16 in said' [Qfi Gazette January 27, 1942.]

I 9,091,439 5 posed electrodes inca able of emitting secondary cousins le tr n oscillati n between said first electrons. adjacent saidfirst pair, means for pair of electrodes to cause secondary emission feeding energy to electrons in the space between therefrom, means for rotating the oscillation said first pair oi electrodes to produce electron path around the axis of said cylinder, and means 5 multiplication by cyclical impact therewith, and associated with said second pair of electrodes 5 means associated with said second pair of elecfor absorbing power from electrons in said rotrodes for absorbing power from said electrons. tated path. 1

17. Incombinatiomapair oi opposedelectrodes a 19. In combination, a pair of opposed eleccapable of emitting secondary electrons at-a trodes capable of emitting'secondary electrons. lo ratio greater than unity, a second pair of opat a ratio greater than unity, a second pair of 10 posed electrodes incapable of emitting secondary opposed electrodes incapable of emitting secondelectrons, said pairs being alternately disposed ary electrons, said pairs being alternately disto describe a symmetrical space, means for ieedposed to describe a cylindrical space, means for ing energy to electrons in the space between said causing electron oscillation between said first pair 15 first pair 01' electrodes to produce electron muloi electrodes to cause secondary emission there- 15 tiplication by cyclical impact therewith, and from, means for rotating the oscillation path means associated with second pairof electrodes around the axis oi said cylinder, means associfor absorbing power from said electrons. ated with said second pair oi electrodes for ab- 18. In combination, a pair of opposed elecsorbing power from electrons in said rotated 20 trodes capable of emitting secondary electrons path. and means for collecting electrons contact- 20 .at a ratio greater than unity, a second pair of ing said'second pair of electrodes due to said opposed electrodes incapable of emitting secondrotation. ary electrons, said pairs being alternately dis- PHILO T. FARNSWORTH. posed to describe a cylindrical space, means for v GERTIFICATEOF comancrror. Patent No. 2,o91,l 9, August 1951 v 91111.0 1'. FARNSWORTHI.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 71;, forthe word "members" read numbers; and that the said Letters Patent shonldbe read with this correction therein that the samemay conform to the recorder the case in the Patent Office..

Signed and sealed this 1 th day of October, A. D. ;l958.

Henry Van Arsdale- (Seal) I Acting Commissioner of Patents.

DISCLRIMER f 2,091,439.-Philo T. Fm San Francisco Calif Mon'rr ANn'AMPmrmn; Ifate'nt dated A st 3l l937. DisJ3:fez- 512a 31 s;31 2:1

R 5b, 1942, by the assig nee, Famswo Television & Radio Corporation.

specifigteioienters this disclaimer to claims 1, 3, 4, 8, 9, 10, 12, 14, 15, and 16 in said' [Qfi Gazette January 27, 1942.]

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