US1711658A - Current-controlling and static-reducing system - Google Patents

Description

May 7, 1929. c. A. SPILQAGUE 1,711,658

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2, 1919 4 Sheets-Sheet l f/yz 2 I Jmcs CURRENT SPACE 040165 mien/0r 6/4/5/706 A. Sprayua M y 7, 1929- c. A. SPRAGUE 1,111,658

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2, 1919 4 Sheets-Sheet 2 JPACF 6 wmflvr f wanna/v5 //v 60/0 MTf/VTIAL f/we/vfor; 674/6006 4. Sp/wgue May 7, 1929. c, SPRAGUE 1,711,658

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2, 1919 4 Sheets-Sheet 3 mm.- 04/6/7064. Sprague fly MA Zy 1929- c. A. S PRAGUE ,5

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2, 1919- 4 Sheets-Sheet 4 v fig 9.

Var/arm in 6nd Parent/kl Patented May 7, 1929.

UNITED sr- -rss PATENT O-FF-ICE.'

CLARENGEA... SPRAGUE, OF EAST ORANGE, NEWJERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEWIYOBK, N. Y., A CORPORATION OF NEW YORK.

CURRENT-CONTROLLING Ann STATIC-REDUCING SYSTEM.

Original application filed May 2, 1919, Serial nafss iees, Patent No. 1,477,017, dated December 11, 1923.

Divided and this application filed November 21, 1923. Serial No. 676,038.

This application'is a division of application Serial No. 294,328, filed May 2, 1919, Patent No. 1,477,017, granted December 11, 1923.

The present invention in its broad aspect relates to a method and means for combining the properties of a. plurality of electric discharge devices, or their equivalents, ar-

ranged in parallel relation, tosecure a de sired resultant property. It involves controlling the order and extent of operation of the discharge devices, which may, for example, be thermionic vacuum tube devices.

. In a more specific aspect the invention relates to the reception of relatively weak signal energy in the presenceof large electrical disturbances. It is particularly adapted to the reception of electromagnetic signal waves at radio receiving stations during atmospheric or other disturbances, but is not limited to such use, since it is applicable, also,

for example, to wire orcable signaling sysmay be temporarily rendered insensitive or.

permanently injured, or at least it may be impossible to receive thesignal during the persistence of the disturbances owing to its being swamped by the disturbing waves. Protective devices are known for preventr ing too large current from reaching the receiver but such devices wipe out the message as well as the excess current. It is an object of the invention to prevent too large current fromreaching the receiver, but at the same timeto permit the signal currents to be received.

A feature of theinvention relates to the method of and means for attenuating currents of abnormal magnitude while permitting signal currents to received. I

Another feature of the invention'relates to the control of asignal current by the abnormal currentfor, determining one or another path currents.

' Another feature of the invention relates to the modification'of the signal currents by the disturbing currents whereby the signal currents persist through the attenuation of the disturbing currents.

A further feature of the invention relates to the separate treatment of the normal signal currents and the currents received during thefdisturbances.

Features concerned in securing the abovemention effects'relate, to the use of discharge devices soar-ranged as to function sequentially or in steps in accordance with the magnitude of the received energ to modulate signal waves in accordance with abnormal currents, and to control attenuationof "the abnormal currents; and other features of the nvention Wlll appear from the fol-- lowingdescription together with the draw- 1ngs, of which Fig. lshows a receiving cir-' C1111} arrangement according to the invention;

lugs. 2 and 3 are curves explanatory of the action of the devlceof Fig. 1; F ig. 1 is a modified circuit arrangement of which the' curves in Fig. 5 are explanatory; Figs. 6

and 7 are other forms of circuit arrangements which the invention may take, andv Fig. 8 illustrates a high power modulator or detector of which the curves of Fig. 9 are explanatory.

Figs; 1 to 6 and the explanations in connection with them serve as preliminary steps in the disclosure of the invention illustrated in Fig. 7 which is a preferred form.

Referring to Fig. l the antenna 1 is connected through adjustable resistance 2 to rate batteries if desired. Plate battery 10 causes a space current to flow normally be for the passage of the'signal tween the filament and plate of discharge device 4 through output winding 11, battery 10' and the secondary winding of couplin 8. The relation between the magnitude or this space current and the potential impressed across the space between filament 7 and anode 8 for a given constant filament temperature it auxiliary tubes 5 and 6 were the total space potential to v ry between thelimits indicated by b, a, the variations produced in the space current by the signals would be represented by the difierence between the ordinates drawn at points 7) and 0.

11 a surge of current from some disturbing source should carry the space potential to some point (5 and maintain it there mo mentarily, the signal variations coming in with the disturbing current would produce no variation in space current, since the saturation point of the characteristic curve A of the discharge device would have been passed, and hence the signals would be lost during the existence of the disturbing current. Discharge device a will act then as a current limiting device, since for a given filament temperature no larger current can be made to flow through it than is represented by the ordinate corresponding to the horizontal portion of curve A.

Electron discharge devices 5 and 6 are substantially like'discharge device 4 but are connected to the common space battery 10 'through respective resistances 12, 13 and potential sources 14 and 15. As shown, source 14 is of less potential than 15 and both sources are connected. so as to oppose the source 10, so that the normal space potential of discharge device 5 is less than that of discharge device d and that of discharge device 6 is less than either of the others. Also the amount of resistance 13 included in the circuit may be assumed to be greater than the portion of resistance 12 that is used, The action of discharge devices 5 and 6 is to permit current to flow in the common output circuit after the cut-off value of the discharge device 1 has been reached. W ith a' space potential (Z for instance, a larger current results than is denoted by the curve A as indicated by the dotted curve B and the ordinate drawn at'rl. However, the current flowing through discharge device or discharge devices 5 and 6 is attenuated by the re sistances 12 or 12 and 13, and the attenuation is greater the greater the currents, as is indicated by the general form of the curve B which maybe considered thecomposite characteristic of the group of parallel discharge devices 4, 5 and 6 as a whole. A large surge of disturbing current is. therefore greatly damped or reduced but the signals are not lost, since it may be assumed that saturation is not reached. 'The effect is graphically shown by the curves of Fig. 3, in which the rent, however, and all such excess current is attenuated by the resistance 12, or, if both discharge devices 5 and 6 are conducting current, by the resistances 12 and 13, and

,the result is that the disturbing current is reduced to some such extent as 1s lndlcated by the curve E which it is assumed represents the wave actually transmitted to the output coil 11. It is evident that the signal wave will also be attenuated but as long as the curve it continues to possess curvature, the signal currents will still be present and are transmitted through windings 11 and 16 to the input circuit of the detector 17 of familiar type and are rendered audible in the receiver 18. A tuning condenser 19 may be used or the detector circuit may be made aperiodic or detuned by opening thekey 20. By thus greatly attenuating the disturbing current this'circuit arrangement prevents a sudden large fluctuation of current from reaching the ear of the operator Owing to the curvature of characteristic B, Fig. 2, the devices 4:, 5 and 6 will act in a measure as a detector. The low frequency signal currents thus set up in the inputcircuit of detector 17 will in part reappear in the telephone receiver 18, by virtue of the repeating action of detector 17 and will, in part, act to modulate the carrier current component, the resultant current not being effective in reproducing the signal" in the receiver 18. Circuit modifications in which this loss of energy does not occur will later be described.

The relative effects upon the operators ear of the currents produced by static disturbances and those due to signals maybe likened to the effect upon the eye of a powerful field of light superimposed upon which is a small weak source of light. It the strong field is very intense, the eye-will be blinded and become incapable ofdiscriminating between the different intensities. If, however, the intensities of both fields are To the left of the line D for instance.

reduced in the same-proportion, there is a certain value at which the discriminating power of the eye becomes greatest; According to the form of this invention just described, the intensity of thesignal and the static are reduced in about the same proportion, with a resulting increase in the clear ness of the signal. According to other forms of the invention the static energy is very greatly reduced while theavailable signal energy is reduced a relatively small amount or isincreased.

The system of Fig. 1 which has been described in detail with reference to a distubing wave of such character as to raise the space potential above that of source 1.0 would need some modification to make it equally eliicacious in reducing disturbances of reverse sign. Circuit arrangements will now be described which are designed to reduce adisturbing current of either polarity and in which the detecting action of the current limiting device taken into account.

Referring to Fig. 4:, in place of the twoelement discharge devices 4, 5 and 6, discharge devices 21, 22 and 23 of the thermionic relay type are shown, each containing in addition to the hot filament and the anode, a .third or grid electrode 24, 25 or 26 respectively; The grid 24 is provided with a polarizing potential source 27 to fix its normal potential with respect to its filament 7 and its potential is indicated as higher than that of its filament. Similarly,

by a source 28, the normal potential of grid 26 is fixed negative with" respect to its filament 7, while the potential of grid 25 is normally the same as that of its filament 7. Source 10 provides a normal potential clifference across the space between filament 7 and anode 8 of each of the discharge devices 21, 22 and 23. If the characteristic curves of the discharge devices 21, 22 and 23 are as represented by the respective curves F, G and H, in Fig. 5, then a normal space current will flow through each discharge device in response to this normal space potential, the respective magnitudes of the space currents through the several discharge clevices being indicated by the length of the ordinate intercepted on the line 0 by the respective curves F, G and H. A'summation curve K obtained by adding curves F, G and H may serve as the characteristic curve of the three discharge devices 21, 22.

and 23 in combination as shown. The zero on their characteristics corresponding to their respective fixed potentials and the abscisszeindicate variations of grid potential from their respective fixed grid potentials. Incoming signal waves vary the potentials of all three grids between the limits h and k,

These signal variations produce very slight changes in the plate currents through discharge devices 21 and 23 as shown by the relatively flat portions of their characteristics F and H respectively, a

that are operated over between these limits, as determined'by the potential sources '27 and 28 respectively. However, the variations of plate current through discharge device 22, due to changes in its grid potential between these limits it and 7c are considerable, as shown by the curve G, and the res sultant curve K shows that in the comparatively linear region ofthe curve K between limits it and 7c the variations in the space current are very nearly proportional to variations in grid potential and the discharge device 22 is acting as an amplifierh These Variations of plate potential as determined by the signal waves are transmitted through the coupled windings 29 into the input oir cuit of a detector 30 of familiar type and are rendered audible in the receiver 81. Thus the normal signal waves picked up by antenna 1 are amplified by discharge device 22 in the ordinary manner, detected by detector 30 of some suitable form, and received at 31 practically without any efiect due to, dis

charge devices 21 and 23. However, if a large disturbing wave carries the grid potential variation to such excessive value as either that indicated at m on the one hand or n on the other hand, one. of the discharge devices 21 or 23 comes into play. It will be noted that the characteristics F and II of discharge devices 21 and 23 respectively, are not so steep as the curve G and that the saturation region for these two dischar e tent indicated first by m, brings the dis charge device 2211p toithe point of its satu ration as seen from curve G, and hence practically no current variations due to the signal are transmitted through coupling 29.

The discharge device 21 is also saturated andv therefore the signal variations are not trans mitted by it. Discharge device 23, however, is operating on a curved portion of its characteristic and is acting as a detector, rendering the signal variations audible in the receiver 34. In this case under the condition assumed, discharge devices 21 and 22 areacting as current limiting devices permitting only current within predetermined limits to pass, while discharge device 23 detects the signal variations and the variable currents which it transmits are attenuated by the resistance'33 before they reach receiver 34. A disturbance in the opposite direction to the extent indicated by a would cause dis charge devices 22 and 23 to act as current limiters, and discharge device 21 would now act as a detector for signal variations. The resultant attenuating effect is perhaps more clearly brought out by the summation curve K which shows that between the limits 7t and 70, including the signal variations as before pointed out, the principal action is that of amplification, indicated by the substantially linear portion of theicharacteristic between these limits, but that beyond these limits in either direction the curve begins to fall off and the total current transmitted bears an increasingly smaller ratio to the incoming currents, but detection of the signals still continues by virtue of the curvature still possessed by the characteristic. lVhen worlv ing over certain small ranges of curve K, signals may be audible in both receivers. The phase shifting means 4E3 may then be adjusted to obtainthe proper phase relations. D

A generator of carrier or other high frequency may, if desired, be coupled to the circuit through coil 36 shown inductively related to windings 3, for the purpose of increasing the strength of the signal or otherwise rendering it more easily readable. A rey 37 is provided in the circuit of the generator 35. Also a tuning condenser 38 may be thrown into or out or circuit across the secondary of windings 3 by key 39. It may be found desirable to render this tuned circuit non-oscillatory by the insertion of suitable resistance. A. tuning condenser 40 is shown in circuit with the secondary of transformer 29. The small condensers 11 and 42 are shown respectively in shunt to receivers 31 and 3a to by-pass the high he quency. current components. The direct current from battery 10 may in any case be shunted past the indicating instrument by choke coils in the well-known manner.

The devices thus far described are designed to reduce the effect of disturbing currents, while still permitting the signal cur-.

rents to be received but the signal currents are somewhat attenuated by the current re ducing means Means will now be shown and described for reducing the disturbing current-s while still transmitting the signal currents strongly. This is accomplished in the particular means shown by causing the lower frequency disturbing currents of large magnitude to control amplification of the signal currents, after which both kinds of currents are attenuated. Referring first to Fig. 6, the secondary of the antenna cou pling 3 is connected tothe input of a balanced amplifier commonly known as the push-pull type. This comprises two discharge devices' 45 and -16, the respective grids of which are connected each to a terminal of the secondary of coil 3, while their respective filaments 4:9 and are connected together and to the midpoint of the said seccurrent.

is connected to the common filament connection and through a combination of discharge.

devices to the midpoint of said primary wlnding. The combination of discharge devices 1n the space current circuit as shown is the same as that of Fig. 1 and. the identity of the various parts may be recognized by the same reference characters as are used in Fig. 1. The action of this combination of discharge devices as described in connection with Fig. 1 and 2 is to limit the current in their common circuit, not by cutting it oi'f definitely at a particular saturation value but at a varying rate somewhat as indicated by the dotted curve B of Fig. 2, so that the signal current variations upon the disturbing waves are not lost. The normal potential of grids 4.17 and t8 is fixed preferably negative by the source of potential 54 so that either device 45 or 16 normally operates over that portion of its characteristic near the transition from the lower horizontal portion to the substantially linear upwardly sloping portion. An incoming signal wave will render one grid, say 17, at any given instant, more negative than normally and since the impedance of this discharge space is already practically a maximum, 'due to its large normal negative potential, there will be substantially no change in its output The same wave will at the same instant make the potential of grid 48 less negative and therefore the impedance of its discharge space becomes lower, and an. output wave, depending upon the extent to which. the grid potential is changed, will result. For an incoming wave of alternating current then the discharge devices l5 and 46 alternately conduct current under control of the input waves. The transmission of space current under control of signal current, while it may be regulated to be normally adequate for the reception of signals, is less favorable than if either discharge device 45 or 4.6 were operating over, a more nearly linear and central portion of its characteristic. duced in one or theqother discharge device 45 or 16 by a suifieiently large disturbing wave of relatively low frequency, since the potential of one or the other grid will be raised momentarily. The corresponding lowering of the potential of the other grid will cause no further increase in the already practically maximum impedance of its discharge space, and transmission of signal current will be through the discharge de- This more favorable condition is pro-v vice which has a momentarily higher grid potential than normal. In other words, the signal currents are modulated in accordance with the lower frequency disturbing waves, and the signals become stronger the stronger is the disturbing current. As inthe case of the arrangement of Fig. 1 the discharge device l transmits the normal signal currents,

- but larger currents than normal begin to 5 and 6 and become attenuated by the 'refind their way through the discharge devices sistances 12 and 13 so that all variable currents ,of abnormally large amplitude in the' common output of the discharge devices 15 and -16 are reduced before they reach the output windings 53 through which they are impressed upon thedetector 55 of familiar type by which they are rendered audiblein the receiver 56. The signal current-s by having been previously boosted may still be as strong as normal, although they have been attentuated together with the disturbing currents.

It will be noted that in the arrangements shown, sharply tuned oscillatory circuits are avoided throughout the path of the received wvave's until after the waves have passed the current limiting and attenuating'means, so

that the possibility o'f'shockexcitation of a resonating "circuit-by a sudden disturbance, whereby an aperiodic impulse is con-' vorted into a series of oscillations in the resonating circuit, 1s 'ZLVOldGd; After the currents have been attenuated there is less probability of this effect and-a tuning condenser in the detector circuit may be advan-' tageous inselectively transmitting only the signal currents. Condensers 19, Fig. 1, 40 Fig. 1 and 57 Fig. "6 are indicated to be used for this purpose if desired. Any suit- 'ableform of wave filter may, of course, be used in place of a single tuned circuit.

Referring now to Fig. 7 the antenna coupling 3 is connected to theinput circuitof a detector 58 of familiar type by which the signals are renderedaudible in receiver '59.

A tuning condenser '60 may be included around the coil winding by closing key 61 if desired. A coupling-3 is also'shown, the secondary of which is connected to the lnput terminals of an amplifier ofl the push pull type similar in general to that of.-

Fig. 6. This pushpull amplifier differs from that of Fig. 6 mainly by having impressed upon the grids of the discharge de vices 64 and 65 a large negative potential from battery 62. It is well known that under this condition the electrons emitted by the filament, when heated, will be forced back thereon and hence no currentwill flow in the plate circuit. This condition w1ll be unaiie-cted by small potential variations impressed. on the grid by normal signals.

received by the antenna system.

The negative potential of the grids of output of the amplifier.

tionas a power oscillator.

devices 64and' 65 is so adjusted that the normal currents are transmitted by the detector 58 and the disturbing currents, if of such large value as to exceed the cut-off value of the detector 58 which value may be suitably predetermined, will change-the potential of the'grids 64 and 65 of the push-pull amplifier sufficiently to enable.

one or the other side of said amplifier to transmit the signal current. The larger the disturbing current within reasonable limits, the greater will be theamplification of the signal currents as explained in connection with Fig. 6 and the signal currents are thus so augmented that the signals are still strong after the currents have passed the large attenuating resistance 66 inthe ings 63 and 67 the output waves are impressed on the input circuitof detector 68 by which they are rendered audible in receiver 59. A. tuning condenser69 is shown which maybe connected across the coil 67 by closing the key 70-if desired.

Fig. 8 discloses a modulator similar to that of Fig. 7 with the addition of tubes '81 to '85 having the required grid potentials By means of windand output resistances to give the operatmg characteristics"shown in Fig. 9, the

'chzwacteristics of tubes 65, 80, 82 and 84 being respectively the same as those of tubes 64, 81, 83 and 85. The'source ofelectromotive force 62iis of such value, as in Fig.

7, as to normallypreventfiow of space current. The two groups of tubes therefore motive force reverses in 1 direction. The

either group beginning with 64cor 65, are

shown at R, S, T and V respectively, Fig.

act alternately as the impressed electro,

operating characteristics of thet'ubes of" i 9, and W is the characteristic of thecombination. It will be noted that the curve 'W' maybe made substantially parabolic over a relatively very wide operating range and that this modulat ng system lstherefore "well ada-p tedifor powerfulmcurrents. The

system may also be used as a detector, and

with proper feed-back circuits, will func- The necessary coupling may be obtained by inductively ord can always be obtained without oblit-- erating the signal.

115 relating coils 63 to coils 86, for example.

, a receiving WVhile the invention has been illustrated and described with particular reference to circuit for electromagnetic waves, it is not to be limited to such a system sinceit is evident that the antenna 1 may be equally well considered as the terminal of a wire line. Also the particular discharge devices illustrated are not to be considered as limiting the invention nor are the relations set out inthe various curves that have been given to be considered as liinitingthe invention but merely as illus-'.

trative oi principles involved and as aids to a disclosure of the invention. Nor is the invention to be limited in other respects by the specific embodiments shown as a whole or to the particular details, but only by the scope out the appended claims.

What is claimed is: V r

1. The method of signaling in the presence of. a disturbing current which comprises automatically increasing the amplification of the signal current as the disturbing current increases and attenuating the resultant current.

2. The method of receiving signal currents in the presence of abnormal currents which comprises automatically reinforcing 'said signal currents as the strength of the abnormal currents increases and then causing all said currentsto be attenuated.

3. The method of maintaining signal currents in the presence of large abnormal currents which comprises automatically reintorcingsaid signal currents as the magnitude of said abnormal currents increases.

apThe method of receiving signals by space discharge devices, each including a control electrode having different values of polarizing potentials applied thereto, to produce different degrees of amplification, which method comprises applying such a polarizing potential to one of said devices as to produce one degree of amplification of received signals in the absence of disturbing energy, and applying polarizing potentials to others of said devices such that under control of received disturbing energy a.

higher degree of amplification for thereceived signals is effected.

5. In a signal receiving circuit, a signal energy absorber, a receiver and two parallel current paths between said energy absorber andsaid receiver, one of said paths contaming a detector and the other of said paths.

said energy absorber comprising two 'discharge devices, each having a cathode, an anode and an impedance controlling electrode, said cathodes having a common connection andsaid impedance controlling electrodes being connected to said common connection in opposite sense relative to the coupling with said energy absorber, a receiver, meansfor connecting said receiver to said anodes, a source of potential connected to said common connection and to said means, and a current-limiting and attenuating means connected between said source of potential and said means.

8. A current limiting circuit comprising a plurality of space discharge devices, a common source of space current for said devices, an attenuator included in the space current path, means for applying to the.

grids of said space discharge devices a biasing potential'of such value that space current is normally prevented from flowing therethrough and means for applying to said grids a potential of such value as to overcome said biasing potential whereby space current is permitted to fiow'through saidspace discharge devices. v

i In. witness whereof, I hereunto subscribe my name this 19th day of November, D.

1923. I V CLARENCE ALSPRAGUE.

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