DE FOREST, AUDON CIRCUIT, 1,377,405, APPLICATION FED APR 27, 1920. Patented May 10, 1921.

O90999.

S, a..." by y. "oral tal UNITED STATES PATENT OFFICE. LEE DE FOREST, OF NEW YORK, N. Y., ASSIGNOR TO DE FOREST RADIOTELEPHONE AND TELEGRAPH. COMPANY, OF NEW YORK, N. Y., A CORPORATION of DELA WARE, AUDION-CIRCUIT. 13,405. Specification of Letters Patent. Patented May 10, 1921. Original application filed April 9, 1915, Serial No. 20,173. Divided and this application filed April 27, 1920. Serial No. 377,051. To all whom it may concern; detected by the operator who at once gen 50 Be it known that I, LEE DE FoREST, a citi erally knows that when the audion is not zen of the United States, residing at New properly functioning it has become par York, county and State of New York, have alyzed. . made a certain new and useful Invention in The Special purpose of my present inven Audion-Circuits, of which the following is tion is to provide means for effectively pre 55 a specification. venting and overcoming this paralyzed con This invention relates to audion circuits, dition of the audion, and while I have and is directed to subject matter divided shown and will now describe my invention O from my co-pending application, Serial as applied to an audion with all of the Number 20173, filed April 9, 1915, for se cathode and anode electrodes inclosed there 60 lective audion amplifier. in and as used as an amplifier or relay, I The object of the invention is to provide do not desire to be limited or restricted an audion circuit which is simple and par either to this construction or particular ap 5 ticularly adapted for amplification usage plication of an audion. of the audion where the same is used as a re Referring to the drawings 65 lay as one illustration for either wire or I show in Figure 1 one audion circuit ar wireless purposes. rangement embodying my invention, and It has been found by experiment that which is a substantial duplication of Fig. 1, 20 relays of the audion type become paralyzed A. my co-pending application above identi when certain conditions in the normal op ed. 70 eration exist. For example, where the de Fig. 2 shows a similar but slightly modi vice, is used as an amplifier or relay with fied arrangement. the current to be relayed and amplified re The same part is designated by the same 25 ceived through an input circuit and the reference numeral wherever it occurs amplified current delivered by an output throughout the several views. i5 circuit, if the incoming current is excis Referring to Fig. 1, I show my present sive too large a charge upon the grid elec invention applied to a selective amplifier trode of the audion causes the same to system of the audion type wherein the 30 paralyze. Similarly, it frequently happens audion will perform its amplifying func that a sudden signal impulse will effect the tion selectively. In other words, incoming same result, namely, the paralysis of the currents or currents of certain frequencies so audion. Also, if the plate current is ex received by the audion will be amplified to cessive the effect of the paralysis is likewise a greater degree than currents of other fre 35 produced. And if a critical adjustment of uencies, and especially currents of lower the plate and filament current sources is se requencies. In addition thereto, the prin cured the normal incoming signal is apt to ciple of selective amplification can be em 85. produce the paralyzed condition of the phasized as much as desired or necessary audion. So it will be apparent that while so that, if desired, the normal voice currents 40 the effect is the same, that is, the audion. before going in on a telephone line, for ex becomes paralyzed, the causes of this con ample, can first be distorted and the higher 90 dition of the audion may be aily one of a harmonics thereof made of greater ampli number. tudes so that after these latter currents are Where a perfect vacuum has not been reduced in amplitude by the distributed ca 45 obtained in the bulb this paralyzed condi pacity of the telephone line, the composite tion of the audion is frequently evidenced current will arrive at the distant receiving by a blue glow or haze although the par station in its normal. or original form. alyzed condition may frequently occur with This feature of selectiye amplification forms out any such visual evidence thereof, and is the subject matter of my application, Se 1877,405 rial No. 20173 above identified, and does not I utilize the same in addition to the uses per se, form the subject matter of the pres hereinbefore set forth as a damping re ent invention except in that the present in sistance to reduce the amplitude of the po vention is disclosed therein. tential surges delivered from the oscillating Reference character 1 designates an ex circuit H, E, to the grid electrodes, as above 70 hausted audion bulb, in this instance of the described. usual well known double plate. and double The natural period of vibration of this grid structure both located within the bulb. oscillating or parasitic circuit depends to It is apparent, however, that I do not desire a great extent upon the amount of induc O to be limited with respect to the particular tance of the coil E and the amount of the construction of the audion, or whether or not capacity of the condenser H. This fre 75 the electrodes are all located within the bulb quency also depends upon the constants of or exterior thereof, as it is well known that the audion itself, the brightness of the fila audions vary somewhat in their construc ment F, the applied potential from the bat tion and in the number of electrodes em tery B, the amount of resistance J, and the 80 ployed therein or therewith. As is custom amount of resistance D which forms a leak ary, however, I have shown a filament elec path between the grids G, G, and filament trode F which is heated from the current F, and is likewise made variable. source A and controlled by the variable re In addition to the first oscillating or para 20 sistance R in the usual well known manner. sitic circuit, if desired, a second similar cir 85 The grid elements or input electrodes G, G, cuit comprising elements C, J, E, H', are preferably arranged on either side of identical with the corresponding elements the filament F and are connected in parallel. of the first circuit may be connected between The wing or plate electrodes W., W., are also the grid and plate electrodes, but the oscil 25 arranged on respectively opposite sides of lating circuit E", H, should be tuned to a 90 the filament F and at a different distance different frequency or natural rate of oscil therefrom relative to the grid electrodes, lation than that of the first oscillating cir G, G. The incoming current to be ampli cuit. Similarly, a number of oscillating fied is led from the line to the primary coil circuits, each tuned to a different frequency, 30 S of a transformer T, preferably a step-up can be connected to the audion. transformer. While I am not to be limited It is not necessary, however, to connect 95 to the specific arrangement shown, I pre Such a parasitic or reinforcing circuit to the fer to have the secondary coil of the trans audion for each different frequency it is de former T wound in two parts disconnected sired to amplify. I have found that one 35 from each other as shown at O, the parts such circuit, the natural fundamental fre 00 thereof possessing a large capacity relative quency of which may be such as to cause . to each other. One end of one winding of it to tend to oscillate approximately 1500 the secondary coil of the transformer T is times per second, will cause incoming cur connected directly to the filament F of the rents having frequencies considerably higher 40 audion 1, while one end of the other coil is than 1500 to be amplified to almost the same 05 connected to the grids G, G, of the audion degree, while at the same time not permitting 1. If desired, in the transformer and grid currents having considerably lower fre circuit, a condenser may be inserted, as quencies to be thus auto-amplified. I have shown in dotted lines at P. The plate or 45 found that two such reinforcing circuits, the wing electrodes W. W., are connected natural period of one of which is such as 110 through an inductance coil of a transformer would cause the audion, to deliver a sus V to one terminal, preferably the positive tained note of a frequency of about 1500 terminal of a source of current such as a bat per Second, if free to oscillate; and the tary B, the current, preferably the negative, natural period of the other of which is such 50 turminal of which is connected to the fila as would cause the audion to deliver, if free ment F of the audion 1. The outgoing cir to oscillate, a sustained note of about 2500 cuit L is connected to the secondary of the per second, will reinforce currents of all transformer V. An oscillating circuit con frequencies between 1200 and 3000 per second. sisting of the inductance E and capacity H It is therefore possible to arrange a single 55 in parallel thereto is connected by one ter audion with reinforcing circuits to so selec minal to the wing or plate electrodes W. W., 120 and the other terminal to the grid electrodes tively amplify voice currents that all the G, G. If desired, and as shown, a capacity higher harmonics are amplified over those preferably in the form of a variable con of the lower or fundamental frequencies. 60 The principles involved in enabling an denser C, may be inserted in this circuit. In audion to amplify different frequency cur 125 accordance with my invention I insert a re rents unequally is set forth in my co-pending sistance J in this circuit, preferably in the application above identified, from which the lead to the grid electrodes G, G, and pref subject matter of this present application erably, as shown, to make the resistance ya has been divided, and while I have gone 65 riable. By making the resistance variable rather fully into the description of the 130 1,377,405 selective amplifier circuit it should be re therein, an incoming circuit connected across 65 membered that my present invention is said heated member, and said conducting directed solely to the resistance leak path member, an outgoing circuit connected across between the elements of the audion, and the said heated member, and said conducting full description of the selective amplifier plate, and an additional metallic circuit con has been given to enable a clear understand necting said conducting member and said 70 ing of one application of my present inven plate. tion to a specific system. . . 4. An electric relay comprising an evacu In Fig. 2 I have shown another circui ated vessel, an incoming circuit, an outgoing O arrangement wherein the incoming currents circuit, a cathode common to said circuits are conducted to one of the grid electrodes and anodes individual to said circuits 75 as G'. One of the wing or plate electrodes sealed in said vessel, and a shunt circuit W' is connected to the outgoing line in the including a high resistance connecting said usual manner. The oscillating or “rein anodes. 5 forcing' circuits are connected to the other 5. An electric relay comprising an evacu electrodes W, G, of the audion bulb 1. ated vessel, a heated electrode, a grid shaped 80 Each of the oscillating circuits contains a member and a plate sealed therein, an in common inductance X associated with the coming circuit including said heated elec coil Z in the output circuit. The individual trode, a condenser and said grid member; an 20 inductances E, E, E, etc., each in series outgoing circuit including said heated elec with the capacity H, H, H, etc., respec trode, a source of potential and said plate; 85 tively, determine the period of the reinforc and a shunt circuit including said grid mem ing circuits, of which in this figure I have ber and said plate. shown three. The effect of these reflection 6. In an electric relay, the combination 25 circuits associated with the output circuit with an audion, of a circuit including a re is to impart to the audion the tendency to sistance in shunt of two of the elements of 90 disproportionately amplify currents having said audion. frequencies generally approximately those of 7. An electric relay, comprising an incom the three reinforcing circuits. In this ar ing and an outgoing circuit, a gaseous con 30 rangement the resistance J is inserted in the ductor interposed between such circuits, and audion path of these circuits to prevent the a conductive shunt circuit connected around 95 audion from singing, and to afford a high said gaseous conductor. resistance leak path as hereinbefore de 8. An electric relay, an incoming circuit, scribed. an outgoing circuit including a gaseous con 35 From the foregoing it will be apparent ductor forming a part of each of said cir that while it is preferable to connect the cuits and a conductive leakage path con 00 high resistance between the two cold elec nected in parallel with a part of said gaseous trodes, especially where the device is to op conductor. . erate as a relay, as shown in Fig. 2, the high 9. An electric relay comprising an evacu 40 resistance path may equally well be con ated vessel, a heated member, a conducting nected between either of the cold electrodes member and a conducting plate sealed there 105 and the hot electrode, in the latter case pref in, and a conductive circuit connected to said erably between the grid and filament. conducting member and said plate. m Having now set forth the objects and na-. . . 10. The combination with an evacuated 45 ture of my invention, and having shown and , vessel having associated therewith a hot and described a construction embodying the two cold electrodes, each of said cold elec 10 principles thereof, what I claim as new and trodes being located at a relatively different, useful and of my own invention and desire distance from said hot electrode, electrical to secure by Letters Patent is circuits connecting said electrodes, and a 50 I. An electric relay comprising an incom conductive leakage path connected to two ing circuit, an outgoing circuit including a of said electrodes. 15 gaseous conductor, forming a part of each 11. The combination with an evacuated of said circuits, and a conductive leakage vessel having associated therewith a hot and path connected to two points in said gaseous two cold electrodes, each of said cold elec 55 conductor. . trodes being located at a relatively different 2. An electric relay comprising an incom distance from said hot electrode, electrical 120 ing circuit, an outgoing circuit including a circuits connecting said electrodes, and a gaseous conductor forming a part of each of high resistance conductive leakage path con said circuits, and a high resistance conduc tive leakage path connected to two points in nected12. The to twocombination of said electrodes. with an evacuated- - said gaseous conductor. w vessel having associated therewith a hot and 25 3. An electric relay comprising an evacu two cold electrodes, each of said cold elec ated vessel, a heated member, a conducting trodes being located at a relatively different member and a conducting plate sealed distance from said hot electrode, electrical 4 1,877,405 circuits connecting said electrodes, and a vessel having associated therewith filament, 20 metallic resistance permanently connected grid and plate electrodes, circuits connecting between two of said electrodes. said electrodes, and a metallic high re 13. The combination with an evacuated sistance path permanently connected be vessel having associated therewith filament, tween the grid and plate electrodes. grid and plate electrodes, circuits connecting 16. The combination with an evacuated said electrodes, and a conductive leakage vessel having associated therewith filament, path connected between the grid and plate grid and plate electrodes, circuits connect electrodes independent of the evacuated ing said electrodes, and an aperiodic circuit 10 space between said grid and plate electrodes. connected between two of said electrodes. 14. The combination with an evacuated 17. The combination with an evacuated 30 vessel having associated therewith filament, vessel having associated therewith filament, grid and plate electrodes, circuits connect grid and plate electrodes, circuits connecting ing said electrodes, and a high resistance said electrodes, and an aperiodic circuit con 15 leakage path connected between the grid and nected between the grid and plate electrodes, plate electrodes independent of the evacu In testimony whereof I have hereunto set 35 ated space between said grid and plate elec my hand on this 21st day of April, A. D. trodes. . . . . 1920. : 15. The combination with an evacuated LEE DE FOREST.