US1465961A - Wireless signaling system - Google Patents

Description

E. F. W. ALEX/ANDERSON WIRELESS SIGNALING SYSTEM Fiied April 19. 1916 2 Sheets-Sheet 1 E. F. w. ALEXANDERSON WIRELESS S IGHALING SYSTEM Filed April 19 1916 2 Sheets-Sheet 2 Fig.4.

lnven tor Ernst FVV. Ne nderspn,

i atented Aug. 28, R9230 entree sraras I eraser Pemeaten,

ERNST I. W. ALEXANDERSON, OF SENIEG'IADY, NEW YORK, ASSIGNOR T0 GENE ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

WIRELESS SIGNALING SYSTEM.

Application filed April 19, 1916. Serial No. 92,156.

To all whom it may concern:

Be it known that I, ERNST F. W. ALEX- ANDERSON, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Wireless Signaling Systems, of which the following is a specification. 9 My present invention relates to wireless signaling systems, and more particularly to a system in which means is provided for over- :oming the effect of static disturbances in the receiving instruments.

Electrostatic disturbances occur continuously in the atmosphere, sending out electromagnetic waves of varying frequency, which will in the description which follows be referred to as strays. These waves are absorbed by the receiving antenna and among the variety of waves absorbed there are always some which are in resonance, that is, which have the same length as a signal which is to be received and consequently act upon the receiving devices in the same way as the signal. Having analyzed this condition both mathematically and experimentally I have come to the conclusion that F a fundamental rule must be the basis of any device used for decreasing the effect of static disturbances. Any discrimination be- 1 tween a wave of the same frequency origi nating from static and from the signal must be based on some difi'erence in character between these two waves. If the strays were like the signals both in frequency and amplitude variation, and in addition to that stronger than the signals, there would be no way conceivable for discriminating between one and the other. The longer the period is during which the strays and the signaling waves can be compared, the greater is the chance for finding a distin uishing difference in the sequence of amplitude variations if in nothing else. In order that the device be effective for discrimination against .strays, it should therefore be designed so that the wave trains can be distinguished by comparing their character for sufficiently long periods. The receiving devices which are at present used commercially are constructed so as to take advantage of this law to a certain extent by using a highly resonant receiving circuit on which the signal can be allowed to act for a considerable number of successive alternations. The reason why these devices do not entirely discriminate against strays is the fact that the receiving antenna is set in oscillation by static shocks and stray waves of short duration and thus I the time during whichthe disturbance can act upon the receiving device is prolonged to about the same degree as the signal.

One of the objects of my invention is to provide a means for prolonging the time during which the signal can act with accumulative effect on the receiving device considerably beyond the time during which disturbances can act.

In attaining this object I make use of a tuned circuit of lower than radio frequency but above audibility, for effecting the prolongation of the time during which the signal and disturbance may be compared. The desired lower frequency is provided by means of interference'beats between two radio frequencies: Both of these frequencies may be produced at the sending station, or one of them may be produced .at the receiving station. I also provide means for roducing, transmitting and receiving th radio frequencies. An arrangement of this kind is more effective than one employing a single radio frequency because it is more selective and proof against interference, both frequencies being nec essary to produce an impression in the receiver. Also when means is rovid d at the sending station-for establishing the beat frequency a less delicate adjustment of frequency is necessary than when the beat freucncy is the result of the difference between two high frequencies. A further object of my invention is to provide means for em.- ciently producing signals of the desired character. Another object of my invention is to provide suitable receiving apparatus for ren dering audible at the receiving station the signals sent from the transmitting station and for enabling the receiving operator to readily distinguish between efi'ects roduced by the static shocks and those pro need by the desired signal. Still another object of I The features of my invention which I believe to be patentable are pointed out with particularity in the appended claims. The invention itself however, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figs. 1, 2' and 3 illustrate different modifications of the circuit connections which may be employed in transmitting signals in accordance with my invention, and Figs. 4, 5, 6 and 7 show different modifications of the receiving circuits which may be employed.

In the form of transmitting system shown in Fig. 1, an alternator 1 supplies current of radio frequency to the antenna 2 through the coupling transformer 3. This alternator is designed to furnish continuous waves of a definite frequency and amplitude. Instead of transmitting the signals by waves of this nature, however, I produce amplitude pulsations in the waves supplied by the alternator of such a nature that the resulting wave may be resolved into two waves of different frequeneies which may be transmitted simultaneously. In order to accomplishthis 1 divide the antenna circuit into two branches and in these branches connect the windings of two ma netic controllers or amplifiers 4 and 5. Each of these branch circuits include half of the secondary of transformer 3 the middle point of which is grounded. he magnetic controllers or amplifiers which ll prefer to use in the present case,

' audibility.

' actions are opposite.

both as to their construction and method of operation, are described in detail in my Letters Patent of the United, States 1,328,797.

Each controller comprises a reactive winding consisting of two coils 6 and 7 wound upon independent magnetic cores 8 and 9. The two coils of each Winding are connected in parallel with each other in the circuit and are so arranged that their magnetizing Each magnetic con troller is also provided with two controlling windings 10 and 11 wound around the magnetic cores 8 and 9 as indicated, so that magnetization produced by the currents in the controlling windings will be in the same direction in both cores. Controlling windings 11 are both supplied from the same source of current, which in the present case may be an alternator 12 of much lower frequency than that of alternator 1, yet having a fre uency above the range of ontrollifig windings 10 are supplied with direct current from any suitable source, such, for example, as

thedirect current generator 13 shown in.

the drawing. The controlling windings 10 are so connected to the generator 13 that magnetic effects upon the controllers are opposite with respect the instantaneous magnetic reactions setup in the mea er controllers by current from generator 12.

The controlling windings 10 and 11 are so proportioned and the current sources 12 and 13 so chosen and adjusted that-the maximum ampere turns of winding 11 is approximately equal to the ampere turns of the controlling winding 10. As a result the controller 4: will have a maximum of controlling ampere turns when the controlling ampere turns of controller 5 is practically zero and vice versa. The characteristics of the controllers 4 and 5 are such that the alent to an open circuit in the connection to the other terminal. After the phase of the controlling current wave supplied by alternator 12 is changed 180 electrical degrees the other controller acts as a short circuit and the first as an open circuit, thus reversing the .polarity of the radio frequency current led to the antenna. At intermediate points the voltage varies between these two extremes in accordance with the sine wave law. The current wave thus supplied to the antenna has an amplitude pulsation substantially in accordance with the sine wave law and the impulses in every other group of waves are opposite in phase to corresponding impulses in the intermediate groups of waves. The frequency of these amplitude pulsations is equal to the frequency or a multiple of the frequency of the alternator 12.

For 'a description in greater detail of the operation of this arrangement reference may be had .to my nited States Patent 1,386,830.

The wave thus produced in the antenna may be resolved into two waves of constant amplitude, one having a frequency greater than that of the alternator l by an amount equal to the frequency of alternator 12 andthe other having a frequency as much lower than that of the alternator 1. If either one of the magnetic amplifiers 4: and 5 were used alone it would be possible to transmit from a single antenna waves of any one of three frequencies, and, by providing multiple tuning of the antenna, waves of two'or more frequencies may be transmitted simultaneously. For example, the variable inductance let may provide for one tuning and th variable condenser 15 in shunt to inductance 16 may provide for a second tuning at a different" requencyf' If, for example, alternator 1 has a frequency of 'Z5,000 cyelres' and alternator 12, 5000 cyc es, the antenatal-nay be tuned for 80,000v and 75,00O.cycles; 80,00()

- and 7 0,000.cycles,or 7 5;000. and70,000 cycles.

iding a third tuned circuit in mul- By prov I tiplewith the antenna-all three frequencies fundamental frequency is suppressed and the antenna. will be tuned for the two. frequen cies into which the resultant wavejmay be resolvcdythat is, one frequency higher than that of the alternator-'1 byv an amount equal to the frequency of the alternator 1. Variable-condensers. 17

; may be connected in series with the windings 6'and 7 of the controllers to neutralize the.

ill

V plitude pulsations} cillating energy storage circuit may be made leakage inductance in the windings thereof so' as to bring the minimum value" of the impedance as-near as possible to a short C1I cuit. It may also 'be' desirable to employ condensers 18 in series with each} branch of the high frequency winding of sucha value that they offer very littleiimpedance to the flow of the high frequencycurrentfrom alternator 1, but a high impedance to currents of the frequency of valternatori'l2; which may be 'inducedin the closed i i formed y the owindingsfi andz7;

is less thanit would be. if it" delivered full I power continuously. To overcome-thisdisadvantage an oscillating circuit may pro 1 vided which is capable of storingupconsiderably more-energy than thealt'ernator-J must give out during "oneiperiod of the ammay be stored up in theoscillating circuit when the energy taken by the antenna is a minimum and when the energy taken by the antenna is a 'maximurn' energy may be drawn momentarily from the oscillating ciredit at a greater rate than the alternator is abler'to deliver, In the presentcase the os up of the primary of transformer 3 and condenser 19'.

In order to transmit telegraphic signals by the system described a. key 20 may be in-' serted in the circuit of alternator 12. When this key is open the impedance of the two controllers 4 and 5 will be equal and since they are connected in opposition to each other no current will be supplied to the antenna. When the key is closed currents having amplitude pulsations will be supplied to the antenna in the manner described.

In Fig. 2 I have shownan organization in of the alternator 12 and the other frequency asmuchlower than that By this meansenergyployed to secure .the desired frequency splitting. In this case a single controlling windwhich a single magnetic controiier 21 is em- 1 ing 22 is shown and the alternator 12 is con- I I ling windings 6 and 7 of this controller-.-arc V connected in shout to the secondary of transformer 3 instead of in series as in the arrangement shown in Fig. 1. An oscillat 'ing' energy storage circuit comprising inductance 24 andcondenser 25 connected in' shunt to. thesecondary of transformer 3 functionsfin a manner similar to that of the energy storagecircuit described in connec-' tion-with the arrangement of Fig. 1, Two different antenna tunings may be secured by means of the variable inductance 26 anithc' variable condenser 27 and inductance 28- in: shunt'toa portion ofinductance 26- In Fig. 3 Ihaveillustr tedanother modiyficationin which the circuit which provides :the second tuning for theiantenna is also utilized as an energy storage circuit. Controller 5'in this case is connected in series with the antenna and controller 4 in a circuit in shunt to the secondary of trans- I 1 v former 3. The main antenna tuning is made 'VVith thesystem whi hhas-been'described' above, in orderv tov producecthe amplitude' pulsations of current, the Outputdelivered by means of variable inductance '30 and the lse'cond tuning by variable condenser 31 "This-condenser in connection with inductanc'es32 forms an energy storage circuit. When controller 4 forms a short circuit if the phase relations of the currents are properly adjusted energy will be delivered to the'storage circuit by means of transformer 33v and when controller 5 forms a short circuit energy will be delivered to the antenna from the alternator and the storage circuit.

. In Fig. 4 I 'haveindicated a simple form IOU of receiving outfit which maybe employed.

for receiving the signals transmitted by the means illustratedin Fig. 1, 2 and3. In

this case the signals made up vof continuous waves having amplitude pulsations which result from the combination of the two frequencies transmitted are received by the antenna 34 which may be aperiodic or strongly damped, so that it will not be set into oscillation by static shocks. The sig nals thus received are impressed upon a cirrcuit which includes the grid 35 of an amplifier-36 of the electron discharge type comprisinga heated cathode 37 and cooperating anode 38 with a battery 39 in the external circuit between cathode and anode. A few of the cells of this battery 40 may also be connected between cathode and grid in order to adjust the grid potential to a value at which the device is most eiiicient in amplifying the received signals. The current flowing in the circuitl'of this amplifier which comprises electrodes 37 and 38, and battery 39, which for conveniencein description I designate the plate circuit, will be a pulsating current. The alternating current component of this current will flow in the secondary of transformer 41 and the circuit 42 which comprises the secondary of this transformer, inductance 43, and variable condenser 44 is tuned to the frequency of the amplitude pulsations of the waves which are to be received. The impulses act accumulatively until the current in circuit 42 has attained its maximum amplitude. If this circuit is a highly tuned circuit the time during which the current amplitude will be built up may be as much as that covered by 100 cycles of the amplitude pulsations; that is, if the frequency of these pulsations is 5000 cycles it may require 1/50 of a second for the oscillating circuit 42 to reach this maximum. If the radio frequency is 50,- 000 cycles the time for the oscillating circuit 42 to reach its maximum may correspondto 1000 cycles of the radio frequency and thus it is apparent that the energy stored in the oscillating circuit may represent the accumulated energy of 1000 Cycles of the radio frequency. The antenna as Well as the secondary oscillating circuit. will also be affected by'static shocks and to a certain degree accumulatively. However, it can be proven by the law of probability that the accumulative effect of successive static shocks in any oscillating circuit increases by the square root of the time in which these irregular shocks are taking place, whereas the oscillations due to the signal, if this is a continuous wave, increase arithmetically until the circuit has approached its maximum amplitude. WVhile it can therefore not be expected that the secondary oscillating circuit will be free from static disturbances, the relative intensity of the signal and the static is greater the longer the time during which the energy of the signal can accumulate. In order to make the signal audible a local source of alternating current 45 of slightly different frequency from that of the current in circuit 42 is introducedin the grid circuit of amplifier 46, so as to create beats in the receiver 47 which is inserted in the plate circuit of this amplifier and detect the-current of secondary frequency by the well known heterodyne method. In previous attempts which have been made to suppress static by tuning for an audible group frequency in a spark system or its equivalent, the operator has been required to distinguish between the signal and static by the pitch of the note which is heard in the receiving telephone. In this case although tuning is applied to the circuit of the audible group frequency and the intensity of the currents produced by static relative to the intensity of the signal has been decreased in somewhat the same manner as that described, there has been practically no gain by reason of this action because of the fact that i the currents produced by static are changed to a pitch for'which the ear is particularly sensitive, and in fact, are changed to a pitch similar to the signal. In my system, however, in which the secondary tuning is at an inaudible-frequency, the receiving device discriminates between currents of the static and the signal purely by magnitude, and the tone pitch at which the signal is received is regulated independently by the heter'odyyne' receiver Withoiit reference to the frequency of the discriminating oscillatory circuit.

In Fig. 5 I have shown a double tuned antenna, the branch of the antenna comprising inductance 48 and variable condenser 49 being resonant to one of the frequencies sent out at the transmitting station and the branch which comprises inductance 50 and variable condenser '51 being? resonant to the other frequency which is transmitted. The two frequencies thus received in coils 52 and 53 will combine to produce amplitude pulsations and these amplitude pulsations may be amplified by an amplifier such as the amplifier 36 in Fig. 4, or may be directly impressed upon the secondary oscillating circuit 42 of Fig. 4.

In the arrangement shown in Fig. 6 I have illustrated an additional safeguard against the transmission of static shocks to the receiving circuit in which an iron core transformer is substituted for the trans former 41 of Fig. 4. This transformer is so designed that the normal strength of a signal will work the iron at its maximum permeability whereas any sudden and excessive shocks by static will saturate. the iron so that full force of the shock will notbe transmitted to the secondary. This transformer is, in other words, a .voltage limiting transformer which is capable of transmitting without saturation a. voltage only slightly in excessof that produced by the signals. As indicated in the drawing the transformer in the present case com- I prises two cores 53 and 54, each having a primary winding 55 and a secondary windmg 56. In order to regulate the saturatiou of this transformer a third winding 57 which is common to the two cores, is supplied with a direct current from battery 58, and the value of the current thus supplied may be adjusted in order to secure the desired degree of saturation.

In Fig. 7 I have shown another modification of receiving circuit in which an inductance 59, which may be similar in structure to the magnetic controllers used at the transmitting station, is inserted in the plate circuit of amplifier 36. The saturation of the iron'core of this inductance is adjusted by varying the current in winding 60 supplied by battery 61 so that increase of current in the windings 62 brings the inductance closer =to-perfect tuning for the frequency of the. current which results from the combination In this way it is possible to design aresult will produce but slight increase'in.

cumulative buildin u of the two sets of waves received. This change in current will change the induc-- tance and this change in inductance will cause a further change in the current, this. process taking place accumulative'l maximum amplitude is reached. his acsembles the self excitation of a dynamo-electricmachine and takes an appreciable time.

cillating circuit with very high ecrement If currents produced by the point of maximum sensitiveness and as v the current fiowing'in the circuit.

In the above description of receiving ap paratus it has beenassumed that the signals which are to be received are produced by means of two different frequencies inthe, manner set forth in connection with Fig's.= 1, 2 and 3; It will,however, be apparent that similar results may obtained by ro-.

, ducinga current havin" amplitude p sasource of current differing therefrom in he.

tions by the interaction between signals produced by a single'frequency and a local uch an arrangement is-illustrated in Figs.

4 and 6 in which a, high frequency source of current 63 is con led to the antenna 34 b means of a coup ing transformer 64 whic may be coupled to the coil 65 which sup-.

- plie s' the, amplifier 36, or may be connected to any suitable point in the receiving sys-.

Y The method (if-and apparatus for trans-,- l 2,5 mitting'signals, shown in Figs. .1, 2 and 30f this application, are described and claimed inmy copending application Serial. No.

,244339, filed July 15,1918, which is a divis sion of this ap lication. I

s for receiv- The method of and apparatu ing signals, shown in F1gs.4, 5,6 and 7 bf i I this application, are described and claimed l in my copending application Serial No.

244,840, filed- July 15, 1918, which is a division of this application. A

It will of course be understood that the.

double tuned antenna may be used with the receiving circuits illustrated Fig. Tas indicatedeither with .or without an ampli fier, and that many modifications may be' made in the arrangement of the transmit- .ting and receiving apparatus without departing from the scope of my invention as set forth in the appended claims;

What I claim as new and desirefto seruntil of the current revtection of this current. j

two sets of waves to interal'ct'to produce a current having amplitude pulsations of a frequency equal 'tothe difference between the cure Letters Patent of the United States, J

simultaneously receiving the waves'of dif-; 1

ferent frequencies, means for causing the two radio frequencies but-above audibility,

, anoscillating circuit resonant to this last frequency, and means cooperating with the oscillating circuit for detecting the signals.

2..The combination in a wireless ,signaling-system of means at a-transmitting station for producing radio frequency currents having definite amplitude pulsations of afrequency above audibility, a transmitting antenna tuned to two different frequencies,

means at a receiving station foichanging the radio frequency currents received into alternating current of a frequency corresponding to the amplitude pulsations of the currents produced at the transmitting station, and-means for the selective reception and detection of this current. 3.'-The combination in awlreless' signaling system of means at a transmitting station' for producing radio frequency currents having definite amplitude pulsations of a frequency-above audibility, a'jdouble' tuned guency by an amount above audibihty;

antenna at a receiving station for receiving signals transmitted by the currents thus roduced at the transmitting station, means 4 or changing the radio frequency currents received by this a'ntenna to an alternating current of a frequency corresponding to the amplitude pulsations of the currents pro- .duced at the transmitting station, and' means for the selectivereception and de- 4.The combination in i; eless 'signaling system of transmitting 'apparatus ;com-' ergy of much lower frequency but: above audibility for controlling the flow of current --fr om the radio frequency source so that. the resultant radiation consists of waves of two radio frequencies differing by an amount at least as great as the frequency of the controlling source, means at a receiving station for combining the currents of two radio frequencies and roducing an alternating .current" of a fiequency corresponding to the frequency of'the controlling source at the sending station, and means for.

the selective reception and detection of the current thus produced.

5. The combination in a wireless signal -ing system of transmitting apparatus comprising a source of;energy of radio freios.

no Y

"Wang 3 mm of energy -radiojfreq y, a S eCOBd controlhng sou'rcejof.en-

' double turied antenna for transmittingwaves' quency, a second controlling source of ener bi ity for controlling theflowof current from J the, radio fr uency source so as to produce amplitude 11 sations therein of a frequency equal to t t of the controlling source, a

' of two different radio frequencies which may be derived from the current having amplitude pulsations, means at a receiving station for receiving and combining the waves of two radio frequencies and producing an alternating current of a frequency corre- 'tion havin the receiving station for combining the waves of two difi'erent radio frequencies to sponding to the frequency of the control ling source in the sending station, and:

means for the selective reception and de-* tection of the current thus produced.

6. The combination in a wireless signaling system of transmitting apparatus comprising a source of energy of radio frequency, a second controlling source of env audibility for controlling the flow of cur rent from the radio frequency source so as to produce amplitude pulsations'therein of a fre uency corresponding to that of the contro lmgsource, a double tuned antenna at a receiving station for receiving waves of two different radio frequencies derived from the current at the transmitting sta amplitude pulsations, means at produce an alternating current of a fre- 'ency corresponding to the frequency of e controlling source at the sending station and means for the selective reception and detection of the current thus produced.

7. The combination in a wireless signal 1 ing system of means at a transmitting station for producing currents of radio frequency having amplitude pulsations'of sine wave formand'of a frequency above audi-..

bility, means for conducting this current through the antenna circuit which is resonant to two frequenciesdiflering from one" another by an amount above audibility in order to radiate two'sets of waves of dif-' tecting the alternating current thus pro-V duced. V

8. The method of wireless signaling which consists in transmittin signals by means of two sets of waves 0 constant amplitude andradio frequency difiering in frequency by an amount above audibility, receiving the waves thus transmitted and combining them to produce an alternating current having a frequency corresponding to the difierof much lower frequency but above King a frequency corresponding quency of the amplitude pulsations of the current produced at the transmitting staence in frequency of the two sets of of much lower frequency but above audiaccumulating the energy of thi alternating? current in a resonant circuit and utiliz g the accumulated energy for the operation of sultable detecting apparatus.

9. The method of wireless signaling which consists in producing atatransmittmg'sta tion a current of radio frequency having amplitude pulsationsof a much lower frequency but above audibility, transmitting signals by means of waves derived from the current thus "produced, receiving the trans- .mitted waves and producing from the reaccumulated energy for the operation of suitable detecting apparatus.

10; The method of wireless signaling which consists in produclng at a transmitting station two sets of waves of constant amplitude and radio frequency differing in frequency by an amount above audibility, transmitting si nals by means of these waves, causing t e waves transmltted to interact at a receiving station to produce alternating current having a frequency corresponding to the difference in frequency of the two sets of waves transmitted accumu lating the energy of this current 1n a reso' nant circuit and causing the current in the resonant circuit to interact with a current of difi'erent frequency to produce current pulsations of audible frequency.

11. The method of wireless signaling a which consists in producing at a transmitting station a current of radio frequency having am litude pulsations of much lower frequency ut above audibility, transmitting signals by means of waves derived from the current thus produced, receivin fi -,1)v

transmitted waves and producing from the received waves an alternating current havtion, accumulating the energy of this current in a resonant circuit and causing the current in the resonant circuit to interact with a current of different frequency to'produce'current pulsations of audible frequency.

12, The method of wireless signaling which consists in producing at a transmitting station a current of radio frequency having definite amplitude pulsations of a frequency above audibility, transmitting signals by means of waves derived from the current thus produced, receiving the waves thus transmitted in a multiple circuit tuned to two different frequencies, producing by means of the waves thus received an alternating current-0f a frequency. corresponding 3o lectively receiving and detecting the. alter- Q CGiVlDQi Ii';

biningthem to roduce an alternating curequency corresponding to to the amplitude pulsations of the current produced atf'the transmitting stationand selectively receiving andv detecting the alter- I, nating current thus produced. w

The -method of-wireless signaling iwhich consists in transmitting signals by *means of two sets of waves of constant am-' plitude and radio frequency differing in frequency/byi an amount above audibility, re-

e waves thus transmitted, com

rent having a the difference in frequency of the two sets of waves, andselectively receiving and detect ing the alternating current thus produced.

14. The method of wireless signaling --which consists in producing at a transmitting station a current of radio frequency having amplitude pulsations of much lower 1 frequency but above audibility, conducting this current through an antennacircuit which is resonant to two frequencies differ ing. from one another by an amount'above raudibility and thereby radiating waves. of 7 --two difierent frequencies, receiving the waves thus radiated and combining them to produce an alternating current having a freuency corresponding vto the difference in requency of. the two sets of waves, and senating currentthus-produced. I 15. The method of wireless signaling which consists in transmitting signals by means of two sets of wares of constant amy plitude and radio frequency differing in frequency by an amount above audibility, receiving these waves in .a-multiplecircuit which is resonantto the two frequencies,

combining the received'waves to produce an 49 alternating current having afrequency corresponding to the difl'erence in frequency of .the two sets of Waves and selectively receiv-.

ing, and detecting" the alternating current thus produced. 2w

16. Themethod' of wireless signaling which consists in producingv at antransmitting station a current of radio frequency having amplitude pulsations of much lower frequency but above audibility, conducting 9 this. current through an antenna circuit which is resonant to two frequencies differing from one. another by an amount above audibilit and thereby radiating waves of two mdi erent frequencies, receiving the sations in the flow of power from a high frequency source in such a way that the character of the signals depends upon sucham- V plitude pulsations, tuning an antenna at one station for more than one frequency so that the continuous wave components into which the wave having-amplitude pulsations can be resolved are transmitted efficiently through "the several corresponding frequencies for which the antenna is tuned, and

recombining the several components into a current havin amplitude pulsations similar to those originally produced.

18. The method of wireless signaling which consists in the use of continuous wave signals having amplitude pulsations, resolving the signal wave into its continuouswave components, passing these components through circuits at one station which are in resonance with the frequencies into which the signal wave has been resolved, and recombin ng these continuous Wave componature to that of the signal current.

19.The method of receiving wireless signals produced'by two transmitted currents of radio frequency differing from each other in frequency by an amount above audibility,

which consists in combining the two currents at a'rece'ivlng station to produce an alternating current havinga frequency corresponding to the difference in frequency of the twocurrents, accumulating the energy of this alternating current in a resonant circuit, and utilizing the accumulatedenergy for the operation of suitable detecting apparatus. l

20. The method of receiving wireless sig nals produced by two transmitted currents of radio frequency differing from each other by an amount above audibility which connents to produce another current similar in I sists in combining the two currents at a receiving station to produce an alternating. 'current having a' frequency corresponding to the: difference in frequency of the two currents, accumulating-the energy of this current in a resonantcircuit, and causing the current in the resonant-circuit to interact with a current-of'difi'erent frequency to produce current pulsationsof audible frequency. I 21."The combination in a wireless signaling system, of means at-a receiving station for producing by means of two continuous wave signaling currents derived'from separate circuits at the receiving station a radio frequency current having amplitude pulsa tions of much lower frequency, but above' audibility, means for producing therefrom, an alternating current having a frequency corresponding to the amplitude pulsations, means comprising a resonant circuit for accumulating the energy of this current, and means for causing the accumulated energy to interact with energy from a source of different frequency to produce a current of audible frequency.

for producing in two separate circuits two currents of radio frequency, one of which corresponds to the frequency of the signaling current and the other differing there 4 from 'by an amount above audibility, means for combining the two currents to produce an alternating currenthaving a frequency corresponding to the difference in frequency between the two currents, and means for selectively receiving and detecting the current thus produced. a

23. The method of overcoming the effects of staticdisturbances in a wireless signaling system, which consists in employing a sig-.

naling .current of radio frequency having amplitude pulsations of much lower frequency, producing from the signaling current an alternating current having a frequency corresponding to the amplitude pulsations and passing this current through a circuit containing a device for limiting the energy passing therethrough to a predeter mined value, and then through a circuit which is resonant to the frequency of the alternating current.

24. The method of overcoming the effects of static disturbances in a wireless signaling system, which consists in transmitting signals by means of currents of two different radio frequencies, receiving and amplifying the signals thus transmitted, producing from the amplified signal currents an alternating current having a frequency corresponding to the diflerence in frequency of the two radio frequency currents, and pass ng this current through a circuit containing a device for limiting the energy passing there through to a predetermined value, and then through a circuit which is resonant to the frequency of the alternating current.

25. The combination in a wireless receiving.

system of an antenna, means'for amplifying signaling currents received thereby, acir- 'cuit through which the amplified current will flow and an iron; core inductance included in said circuit, the core of said inductance beng saturated? to sucha degree that the current which will flow through theinductance cannot exceed a predetermined desired value 26. In a wireless receiving system, an oscillating circuit, an iron core inductance in said circuit and means for adjusting the permeability of said iron core, the iron core being normally so adjusted that the time required for oscillations to build up to a maximum is greater than the time corresponding to the natural oscillations of a circuit having corres onding inductance and capacity.

27. he combination in a wireless signal- 'reeaeei ing system, of -a receivng antenna having two branches tuned to two radiofrequencies difi'ering; from. each. other by an amount 22. The combination in a wireless signaling system, of means at a receiving station two radio frequencies differing from each other by an amount above audibility, means for producing from the-waves? received thereby an alternating current having a frequency corresponding to the difference in' frequency of the two sets of waves received,

and means for selectivelydetecting th'e'current thus produced.

29. The combination in ai wirele' s s signaling system, of means at a receiving station for simultaneously receiving signal waves of two radio frequencies differing from eachother by an amount above audibility, means for-causing the two sets of waves to interact to produce a current having amplitude-puldifference in frequency of the tw'o currents received, and means in the receivin circuit whereby the energy of the current t usp'ro- .dueed may be accumulated for a greater length of time than the nauraljoscillations of the radio frequency current? afg 30; The combination in a wireless signaling system, of means at a receiving station for simultaneously receiving signal Wavesof; two different radio frequencies, Imeans-zfor' causing the two sets of waves received to interact to roduce a current having amplitude pulsations of a frequency. equal'to the difference between the two radio frequencies,-

but above audibility, an os'cillating circuit resonant to this last frequency and means cooperating with the oscillating circuit for detecting the signals.

' 31. The combination iii'a wireless "signal-' ing system, of means at a receivng station a no if for simultaneously receiving signal waves of two different radio frequencies, means for causing the two sets of waves to interact to produce a current having amplitude, pu1-' sations of a frequency corresponding tothe difference between the two radio-frequencies,

and means in the receiving circuit whereby the energy of the current thusproduced may be accumulated for a greater len' hyof timethan the natural: oscillations 0 frequency currents.

32. The method of receiving wireless signals produced by two currents of radio frequency differing. from each other in fre'-'.

quency byan'amount above audibility, which the radio ernating CUT-3' x30 7 90 sations of a frequency corresponding-to the p the difference in frequency of the waves received and selectively detecting the alternating current thus produced. I

33. The method of receiving wireless signals produced by two currents of radio frequency differing from each other in frequency by an amount above audibility, which consists in utilizing an antenna tuned to the two fre uencies, producing by means of the waves t ereby received an alternating current having a frequency correspondlng to the difference in frequency of the two sets of waves received, accumulating the energy of this current in a resonant circuit and causing the current in the resonant circuit to interc act with a current of different frequency'to produce current pulsations of audibile freiqu y- 34. In a wireless receiving system, an oscillating circuit having an iron core inductance included therein, said iron core inductance being so adjusted that an increase of current accumulatively changes the inductance in the direction required for exact tuning to a desired frequency whereby the circuit is made so sensitive as to approach instability. Y I 35. A receiving device for a wireless signaling system, comprising an oscillating circuit having therein an iron core inductance and means for adjusting the saturation in the iron core the saturation of said iron core being normally adjusted so that the oscillating circuit approaches a state of instability. on account of the change in permeability of the iron with changes in the current in the circuit. 36. A receiving device for a wireless signaling system, comprising an oscillating cir- ,-cuit having therein an iron core inductance T, which has, in addition to the alternatlng current winding, a winding supplied by a variable direct current for adjusting the saturation in the iron core the saturation of said 4 iron core being normally adjusted to such a point on the saturation curve that the oscillating circuit approaches a state of 1nstability on account of the effect of the alternating current'upon the permeability of'the iron, whereby the time required for building up oscillations to a maximum is prolonged beyond the time required for a corresponding circuit with constant inductance.

37. In electrical signaling, the method which consists in producing a signal-representing undamped current of radio frequency varying in amplitude at predetermined lower frequency above audibility,

converting the same into a current of frequency corresponding with said predetermined frequency, producing a current reacting with said converted current to produce beats, and utilizing said beats whose 7 frequency is the diiference'between the fre quency of said converted current and the frequency of said third named current to reproduce the signal.-

38. In electrical signaling, the method which consists in producing a signal-representing undamped current of radio frequency varying in amplitude at; predetermined lower frequency above audibility, converting the same by rectification into a current of frequency correspondingv with said predetermined frequency, producing a current reacting with said rectified current to produce audible beats, and utilizing said beats whose frequency is the difference between the frequency of said rectified current and the frequency of said third named current to reproduce the signal.

39. The combination with transmitting apparatus comprising means for producing sustained high frequency energy varying in amplitude at a predetermined frequency, means for'controlling the energy to represent a signal or message, of receiving apparatus comprising means for producing ,a current of frequency differing from said predetermined frequency to produce beats, and a translating device utilizing the beats whose frequency is the difference between said predetermined frequency and the frequency of said current to reproduce the signal or message.

40. In electrical signaling, the method which consists in transmitting a signal-representing current of radio frequency varying in amplitude at predetermined lower frequency, producing a current of frequency reacting with the received current to roduce beats, and utilizing said beats w ose frequency is the difference between said pre-.

determined frequency and the frequency of said slecond named current to reproduce the signa 41. In electrical signaling, the method which consists. in transmitting a signal-rep resenting current of radio frequency varying in amplitude at predetermined lower frequency above audibility,'-producing acur- 'rent of frequenc reacting with the received current to pro uce beats of audible frequency, and utilizing said beats whose frequency is the difference between said predetermined frequency and the frequency of said second named current to reproduce the signal.

In witness whereof, I have hereunto set my hand this 17th day of April, 1916.

ERNST F. W. ALEXANDERSON.

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