US1992441A - Single side band transmission and reception - Google Patents

Description

Feb. 26, 1935, s pURlNGTON 1,992,441

I I SINGLE SIDE BAND TRANSMISSION AND RECEPTION Filed Sept. 6, 1930 2 Sheets-Sheet I :zza

8/) IRAMS 61/77 ER INVENTOR ELUSON S. PURINGTON BY 7*% ATTORNEY k mm 00 an l mm B A S T llllllllllll ll i q. C V 2 m W G 1 H n m a V ma 4 ESE: M Q

Patented Feb. 26,1935

S, JPATE NT arms 14 Claims.

This invention relates-to' a method of single side band transmission and reception. More particularly it relates to'a method of single side band transmission in which, due to the suppression of the carrier frequency componentat' the transmitter,.it is necessary, inorder to reconstruct the audiosign'als, to supply at the receiver a carrier component the frequency of which'should very closely. approximatezthe frequency of the carrier. component originally suppressed;

This invention further relates to, the secret transmission and reception of intelligence by the method of single side band transmission, in which the suppressed carrier frequency is wobbled durcurrent at the receiver, is appropriately varied as to frequency so as to produce intelligibleaudio Therefore,wonelobject of thisinvention is to provide a method of and apparatus for single side band transmission. 1

- Another. object'of this invention 151 5 provide a method of and apparatus forthe receptionof single side band transmission.

A further object of this invention mission of intelligence by the single side Lband method.

. 7 in drawings. l

A still further object of thi's'inventicn isv to provide for the reception of'secret transmission by the single side band transmission method.-

A more specific object of thisinven'tionis to provide a method of and apparatus forthe controlqof the heterodyne required'in reception by the single side band transmission method, which includes. the transmission of, frequency-component.

These and further objects of this invention will become apparent, from the following specification taken in connection with the accompanyan auxiliary tone In transmission of intelligence by the single side band method, it is necessary to maintain an oscilla'tora'tthe receiver in synchronism with the highcarrierfre'quencyoscillator at the transmitter to within'a, small degree .of variation; ;-In

order that the quality. of the received signal shouldbe good; it is'necessary that theifrequency f of the receiver-oscillator should be within130 ing transmission and the reconstructing carrier 7 is to provide amethod of and apparatus for the secret transtransmission and the lack oftechnique for prop erly receiving single side band transmission.

- My copending applications Serial Nos. 480,165

and 480,166 vfiled concurrently: herewith cover methods of producing high frequency single side band transmission, and thus overcome the first difiiculty noted above... V The present application covers a correct receiver for single side band reception, showing a methodofmaintainingthe high frequency oscilm lator'at the receiver in synchronism with the carrier: frequency oscillator at 1 the transmitter.

above. 1 L The transmitterused to transmit the single side band signal may be of the type indicated, in

.It'thus. overcomes the second difficulty noted either my copending application Serial No;

480,166 filed September'd, 1930, ormy copending application Serial No. 480,165 filed September: 6,

1930, or of any other suitable type of single side 7 bandtransmitter ,wherein. the carrier frequency energy is suppressed. V I

.In addition to side, band components representativeof the voice frequencies, in accordance with the present invention, I introduce into the side band a component representative ofa fixed audio tone of, for example, 6,000 cycles'which is of a frequency above; the audio frequency tone range required for good speech ormusical transmission. This tone is for the purpose of adjusting the high frequency introduced in reception and is in itself eliminated from the final receiveroutput. r

The auxiliary tone at duced by a constant frequency source; and a-simithetransmitter pro-jlar source-although of differentfrequencyisf.

tained correct to within two or three cycles per, second without any particular dificulty This may be done by any. constant speed motor or elecprovided at the receiver; It is obvious that the 1 frequency of these sources may be easily maintricallydriven tuning fork, etc., the details of i which; constitute no part of the present'invention.

:The pitch of the auxiliarytone as reproduced at the receiver, which pitch,.it is, to be understood;

is dependent upon. the frequency of the high frequency oscillations supplied at the receiver, is compared with the pitch of the locally produced tone frequency. The comparison is accomplished by means comprising amplifiers adaptedto supplythe'driving magnet of a set of reeds tuned to and adapted to vibrate at the normal tone difference or beat, and frequencies slightly above and below thisfrequency. These 7 and the adaptation of my method of 3 control in' aiding the supplying of the suppressed carrier frequency current at the receiver, carefully matched with that at the transmitter as regards frequency wobble rate and degree" of frequency variation.

' Having thus briefly described my invention,

attention is invited-to :the" accompanying; draw-l ings in..which; v

' Fig. 1 represents'the frequencyrspectrumine volved in transmission of intelligence in accordance with my single side'bandtransmssion SYS':

'tem. J J

Fig. 2 represents the frequency spectrum in; volved in the receiver operating in accordance with my invention:v V l 'Fig. 3 represents a'i'circuitfor transmitting intelligence in accordance with my invention.

Fig. 4 represents a circuit for receiving single side band transmission in-accordance with my invention. I

Fig. 5'is a detail of the'frequency controller for use in reception indicating: its .relation to the receiver of Fig. 4. 1 y Fig.' 6 is' a diagram indicating a transmitter for secret transmission employing single side bandtransmission. J

Fig. 7 is a receiver for the ofFig. 6. 1

Referring more particularly to-Fig. .1, the carrier frequency'bywhich the single side band transmission is produced is representedat C, and the side bandtransmission is represented at S, and the side frequency representative. of the auxiliary control frequency is.irepresented as A.. Thus the-total transmission represented secret transmission as T may extend from the allocation of the care rier frequency 0 to the side band representative of the auxiliary'frequency A.

In Fig. 2, which represents the 'frequencies'at the receiver,- C represents the high frequency oscillations supplied to combine with the side frequencies S" which are received from the transmitter and also with the auxiliaryside frequency A similarly received. 1." Referring now more particularly-to Fig. 3, the intelligence which istobe-tran'smitted is'i1n-. pressed through the microphone 10 .and the transformer 12 uponthe grid of the combining tube 14, and the high auxiliary audio frequency .A of, for instance, 6,000 cycles produced by .the oscillator circuit 16, is similarly impressed .upon the grid'of the combiningtube' '18. Combining tubes 14 and 18 have a common plate circuit including the high potential source 20 and the primary 22 of the output transformer 24. The devices 14. and 18 are supplied with low potential and biasing source in the usual manner as shown. Inductively related to the primary 2-2 of the transformer 24 is the secondary 26" which suppliesthe combined voice and auxiliary frequencies to the single side band transmitter 28,

which transmitter is of the type as shown in either of my copending applications.

This transmitter produces the high carrier frequency C. The audio frequencies and auxiliary frequency A, supplied through the winding 26 serve to modulate the carrier C, and the transmitter is adapted to transmit the frequency band T as indicatedin Fig. l, but the high carrier frequency C is not transmitted. This output energy is radiated by means of the antenna system 30, and the usual groundconnection 32 in the usual well known manner.

' Referring now more particularly to Fig. 4

which shows a receiver adapted to cooperate with the. transmitter of Fig. 3, the incoming energy is absorbed by antenna '40 in conjunction with the ground 42 and input inductance 44. The energy thus received is supplied to the tuned input circuit 46 and is in turn impressed upon the grid of the beat detector device 48. Also impressed upon the grid circuit of the device 48 is the highafrequencycurrent Cysupplied by the high frequency oscillator generally represented at 50, through the transformer 52 and across the terminals Z.

Fig. 2 shows the relation of the radio frequency currents. The output of the detector includes currents formed by beating of C with S, and C with A'. These currentsare of the frequencies produced by oscillator 16 and microphone 10 provided that C equals C.

The low frequency components .ofv this. energy are supplied to the amplifier .56 and to any appropriate amplifiers as'required, and the energy asthus amplified is supplied through the transformer 58 of the inputsof filters60-and 62.

Thefilter 60 is adapted to cut out all high frequencies and thus eliminates from the result of detection and amplification process the high received audio: frequency 'A, and thus'permits only the desired voice currents to pass to the audio amplifier 64; The, audio voice. currents are thus amplified'and supplied to the receiver which may be of anydesired type.

.Filter 62 is-adapted to. pass only the high received audio frequency. component A which "is supplied to the amplifier devices 65 and'66. The latter amplifier supplies thisenergy to the fre quency controller 68 through the terminals X. The controller 68 is also supplied through the terminals Y with a high audio frequency current A, the frequency of which is regulated to differ from the high'audio frequency A supplied by the source 16 .of Fig. 3.by a predetermined amount. The frequency controller 68 is adapted to control thefrequency C produced by the high fre-' quency source 50 by means of the control rod R, which control action will be'clearly described in connection with Fig. 5 to which attention is now invited.

The operation of the frequency controllerwill become'more apparent from a considerationof Fig. 5 to which attention is now invited. The frequency controller consists of twocombining thermionic devices 82 and 84 operating as detectorsor :rectifiers. These combining tubes are supplied with .the received high audio frequency A, and the locally generated high audio frequency A through the terminals Xand Y as providedin the outputs of 66 and respectively.

The output of devices 32 and 84 include a common high potentialsource and-an impedance, as showmand the beat-frequencyis adapted to be supplied through a condenser to the primary of the audio transformer 86. The'secondary of the transformer 86 is adapted to. supply the coil 88 ofan 'electromagnet which is adapted toex-t cite thehreeds which aretuned to various frequencies. which may be expected to existnas' will be explained moreiiclearl y hereinafteri i For forming contact *withthe vibrating reeds 90, there.are provided-aseries of "contacts 92 which are connected to=diffrentpoints in the re sistor 94.;Across'the resist0i'r94wis-provided a low potential sourcegcomprising, twoysections 96 and.98, the .entire source ,of Twhichis adapted to supply the .field 100 of motor:101. -The armature 102 of motor-.101 "is supplied by: a variable voltage,

. as shown, depending upon .which of the contacts 92 closes, as will .bedescribedmore clearly hereinafter.

Rotation of the armature;l02ifof the motor. 101 is reduced through gear; 80-.and. is supplied throughthe rod R to rotate aycdndehserflfi.

. Generally indicatedat 50, as-rdiscussed inconnection with Fig. 4, isthe high-freguencysource adapted to supply the;ghighjfrequency.current to replace the .suppressedcarrier inorder to receive the single side .band transmission This current is supplied through the "terminals" Z of Fig. 4 to. the inputof device 48, as was dised bq in The oscillator;- .is in theformgof a vacuum tube oscillator with suitable shield and tempera ture control. It-comprisesathermionic device and its associated circuits. The control 011- cuit for controlling the-frequency of the oscillations produced is generally representedat 72 and includes condensers "74 and 76. Theformer of thesecondensers is adapted'to; be. adjusted by hand, and the latter is adapted to be regulated other words, with a high .audio' frequency], of

6,500 supplied .byfthe source 700f Fig." 4, when the high frequency current supplied'by oscillator 50 is of normal frequency, the highfrequency one direction,.but the'ldirection and strength of audio component A will b.e 6,000 "the difie'rence frequency will 500;; and the ce'nter reed 91: 1

will vibrate. i r I The fieldcurr'ent asabo'vejis at all" times in the armature currentjandjtherefore, the .direc tion and speed ofjthe armaturerotation is determinediby the difference of. the generator auxiliary'frequency A.., lasproducedflby the source 70, and the difference frequency"A'5C".the lat-.

ter being the carrier-Supplied. by the sourcefiilc This difference will be of-theforderof 500 cycles when normal. .voltage of the. frequency. A' C" is impressed upon the tube 82 of Fig. 5,.and lvoltage of the frequency. A.'"Iis impressed upon the tube 84. These tubes exhibit plate rectification and thecommon impedance carries a current of the difference frequency nominally (Al' -Q) A". which wouldnormallybe 500 cycles for the example given. .The:current of this frequency is impressed upon the Sfr'equency meter causing closure of the contact 91 to ground. When this reedis actuated,.nc current flows toethe arma ture since the reeds between the :contacts are i so arranged: that contact-forreed 91 is equal potential with the junction pointofthetwo hat 7 teries 96, 98.

. When however other of contacts close current is suppliedtoarmature 102. causinguit to .rotate in'such. a direction asto vary the frequency generated by 50 until the normal frequency (A -C")-Af. exists.

For thatpart of my inventionwhich includes secret communication,=I utilize in general a system outlined above with; however, the1modifica-, tions which will now be described.

-The frequencygcontroller which has just been described will only operataat a perceptible time interval, and therefore, wouldnot be suitable to cause-the frequency at the. receiver to follow,a rapidlyjvarying,frequencybeing emitted by the transmitter. Therefore, in order to .obtain sec'recyin which a rapid variation rate is necessary, a motor isutilizedto vary the carrier frequency at the transmitter and a similar motor to vary that atlthe receiver. Thejlatter motor would control thefrequency ofthe-generator. for;

' supplying the carrier, frequency. This motor be:

ing driven synchronously with that which varies the carrier frequency atthe transmitter by means of a method such as is shown in my copending application Serial No. 313,713, filed October 20, 1928. i

The method offrequency controlling outlined above is added to the synchronizing arrange; ment in order to correct for. any small variation in frequency due to differences in the transmitter and receiver ,high frequency. circuits, and also to correct for changes or variations in the fundamental transmitter high frequency.

Having thus briefly described that part of m invention which relates to secret transmission of intelligence, attention is now invited to Fig. 6 which shows a; transmitter suitable;v for trans: mitting in accordance with this part of my invention- At 128 is indicated a single side band transmitter similar to transmitter 28 of Fig. '3. This transmitter is adapted to radiate single side band transmission-by means of the antenna circuit including the antenna 130 andtheground 132. For supplying the high carrier frequency for usejin the. side band: transmitter, theregis provided a carrier frequency generator indicated.

at ill, the frequency of. which is in'partcone trolled by. the condenser i 14. fThis condenser is varied cyclically by means of the: Wobbler motor 112.: The audiolfrequencyto be transmitted i is .supplied through the usual microphone 'cir cuit including themicrophone 110 and the auxiliary frequency is supplied by a generator 116 whichis similar'to th'e generator 16' of'Fig'J 3. There is thusemitted from the transmittenof. Fig.6. a'spectrum similar 'tothe spectrum T of Fig. 11,; except that the} location of this spectrum will be continuously varied due carrier frequency.

to the. change in Referring now to Figf'l, the incoming-energy is absorbed bythe antennafcircuit including antennal40 and ground i421, and is supplied to the receiver and detector 'l44 fwhich is similar to the amplifier and detectercircuits shown in Fig. 4. Theoutputof the detector 144 is supplied-through the low pass filter and signal amplifier 160 to the receiver 164 in the same manner as the receiver 64 of Fig. 4 is supplied. In Fig. 7 the generator 50 of Fig. 51 is replaced by the high frequency source ;"the'frequencyof which is controlled by condensers l5l andj Condenserliil is so arranged'as to have its capacity'cyclicallyvaried by means of thewobbler motor 152 which isoperated synchronously-with wobble'r motor ll2'of Fig.6. v

Thevhigh pass filter 162 serves to" supply" the auxiliary. high audiofrequency a to the frequency controller'168 which is similar to the controller shown in Fig. 5. The source 170 serves to supply the frequency controller 168 with the controlling highaudio frequency a". The frequency controller 168 serves to vary condenser 133 in order that the frequency, generated 'by'the high frequency generator 150 'may be correct to give the properaudio tone to thesig'nals' 'sup-plied to the receiver-164; The operation of thus controlling the frequency of 150 is in all'particulars the same supplied through thetransmitter 10 and thehigh auxiliary audio frequency a which'is normally 'above the audio frequency range necessary for good reception; Thus the output of 'the tran's mitter 2 8 of Fig. 3 will comprisean' audio fre-- quency side band S and above it a side frequency A. At the receiver after detection, filters are pro 7 vided to separate the audio 'component s' of the 'Fig. 5;

said detection so that from the resistor in the input of device 62' of Fig. 4, the high audio frequency currents will be eliminated. Thisthen permits only the speech frequencies s'to pass through the filter 60 to the receiver amplifier 64. The filter 62,"on the other hand, filters from 'the' audio components of detection" passing through the transformer 58 all of the'l-low' audio frequencies, thus permitting only the high audio component a to pass therethrough. This audio frequency a is supplied to the frequency'controller through the connection Xjof Fig. 5. An auxiliary high audio frequency currenta", supplied by the'audio frequency generator 70 is similarly supplied to the frequency controller through the terminals Y, of V The'frequency' of source 70 may be; for instance, 6,500 while the auxiliary frequencymur rent at the transmitter a may be of la frequencyof 6,000. There thus' exists' inthe output of the combining tubes 82 and'8 i a beat frequency of the order of 500or'a," (A" C). This beat fre quency is supplied to the "winding 88 and is adapted to operate upon thevibrating reeds 90. It is obviousthat if these reeds are tuned to different audio frequencies as discussed above'of, for instance, 440, 460, 480, 500,520, 540 and 560 cycles per second, they will set into'vibration when the corresponding beat frequency exists in winding 38. Contacts 92 are arranged in contact with the various"reeds when they vibrate, and these con tacts are arranged to complete the armaturecirf cuit of the motor'101 to cause it to rotate in differ.- entdirections. Y Y

This is obtained by means of the split low power source 96- 98 and the resistor94 whichis divided into varioussections by, the contacts 92. When, for instancathe reed 91 closes with" its contact, there will be no voltage' impressed upon the ar mature 102 but when other of the contacts are closed, .due to the beat current being incorrect, the armature 102 will cause the rotor of condenser '76'to rotate in the proper direction to so alter the carrier frequency produced by oscillator'50 as to correct the incorrect beat frequency then existing.

rier frequency of the transmitter result in a similarv alteration in the'auxiliary carrierfrequency supplied'at the receiver. With respect to the secret transmission)" the intentional variation of the carrier frequency, as caused by means of the Wobbler motor 112 of Fig. 6, will cause a cyclic variation in the-location of the spectrum T of Fig. 1. The Wobbler motor 152 of Fig. 7, which is synchronized with 112' of Fig. 6, causes a variation in the frequencyproduced by the carrier frequencygenerator150,'and the frequency controller168 which operatesthe same as that of Fig.

5, will"cause the condenser153 to control the fre-v quency generated by the carrier frequency generato'r-150 so as to cause it to'be at all times correct in spite of irregularities due tovariations in condensers-power, voltages, etc.

' Having thus described myinvention, attention is invited-tdthefact that various modifications may be madawhich come within its spirit and scope, andthat 1am therefore not to be limited good 'au'dibility, modulating the carrier frequencyv current by'said'auxiliary frequency current, and thus includingin the'transmission of said transmitterja side frequency representative of said auxiliary frequencyygeneratinga current-of an auxiliary frequency at the receiver having a normally small' difference, frequency with respect to the frequency of the auxiliary current at the transmitter, generating a current of the carrier frequency, thefrequency of which it is desired to control, wobbling the frequency of said locally generated carrier frequency current to correspond s'ubstantially'to the wobble of said carrier at the transmitter, receiving the transmitted side band, 1

detecting said sideband by the use of said locally generated carrierfrequency current, separating fromthe product of said detection the high auxiliary current representative of the auxiliary 'm'odulating current at said transmitter, comparing the'frequency of the auxiliary current as thus detected and that locally generated and producing a beat frequency therefrom, changing the beat frequency energy into corresponding frequency mechanical vibrations and "controlling the frequency of the locallygenerated carrier frequency 7 reception, the method of controlling the frequency of the local heterodyne at the receiver-to correspond 'to, the suppressed carrier frequency current of the transmitter which comprises generating a current of a carrier frequency, wobbling thefre'quency of said' carrier current, modulating 'the carrier frequency current by a high auxiliary-frequency current and thus'including in the transmission of said transmitter a side fre- I chanical vibrations.

, quency representativeof. said auxiliary frequency, generating atthe receiver a current of an auxiliary :freque'ncy. having r, a. normally "small :dif-

ference frequency with; respect to 1the frequency of the auxiliary currentat, the transmitter, en- 7 V crating a current of the a carrierzfrequency; the

frequency of whichit is desiredto control, wob- ,pressed carrierrat thentransmitterh J bling the frequency. of 'saidlocallygeneratedcarrier frequency current .to, correspond. substantially to the wobble of saidycarrier at the transmitter,

receiving and'detectingthe high auxiliaryccun rent representative-of: the auxiliarymodulating' current at thetrarismitter, comparingxlthegrfrea quency of theauxiliary current as thusdetected and that locally generated, producing a beat frequency resultingc..from said comparison: and

changing the beatffrequency energy into corresponding frequency mechanical vibrations; and controlling the frequency. of thelo'cally generated carrier frequency in accordancewith the frequen,

031' of the mechanicalvibrations whereby the frequency of said locallygenerated'carrieris maintainedsubstantially the'same as thatof the sup:

11 3. .The method ofsecretsingle'side bandtranse mission and reception which comprises producing and radiating a single side band representative r the intelligence to Flier-transmitted, fwobbling the frequency of said side band; including in said side band-a side frequency representative of a high frequency auxiliary": current; receiving :the

side: band thus transmittemfproducing a local heterodyne, wobbling thefrequency of said heter odyne to correspondto the wobble ,of theradiated side band, locally generating athig h frequency auxiliary current: differingginfrequency from the auxiliary current, 'atythe transmitter by a predetermined amount, detecting from the I received energy the auxiliary. current" representativer of the L auxiliarycurrent, at; the. transmitter; :combining this latter currentv with: the; locallygen-z erated auxiliary current to producea beat-frequency current, changing said currentinto :cor-

responding frequencymechanical vibrations, and controlling the, frequency. of theLlocal heterodyne in accordance with the mechanical vibrations.

' i '4. The method. of secret: transmissiont'and re-r ception which comprises producing a single-side band transmission by .the use .of as suppressed wobble carrier-frequency; ;said transmission in cluding in addition :to frequenciesirepresentative of :the intelligence to be transmitted a side ,frequency representative of'aj high audio-frequency control current, producing a similar high fre quency control current at .the receiver, detecting the incoming'energy by the ,useof alocal heterodyne wobbled similarly to the wobble.,of the ,suppressed ,carrierat the transmitter, detecting the current representative of the high auxiliary con trol currentiof the transmitter, combiningthis detected current with the locally;ge'neratedauxiliarycurrent to produce abeat frequency, changing the beat frequencyenergy into corresponding 'mechanical vibrations andtcontrolling, the mean frequency of the local heterodyne*bythem- V 5; The method of secret ception basedupon; the wobbledj carrier, suppression system which comprises radiating: a :wobble'd 7 side band including in addition to frequencies representative of the intelligence to be trans: mitted, a frequency representative of a fixed auxe iliary frequency current, at thereceiver-generating a second fixed auxiliary frequency, current having a 1 predeterminedffrequency relationship ofithe wobbled localheterodyne current used in the detection of said'current, as well as in the detectionfofzthe audio frequency currentrep- 'resentative of a the intelligence to be transmitted.

.6 .1 Apparatus forsingle side band transmission andzreception comprises meansfor, gen-'- erating a,carrierzfequency-current; means for generating a current of" an auxiliary frequency above good audibility, means for continuously modulating ,the carrier current by said auxiliary frequency"current,,meansfor modulating the carrier current by -a ,currentrepresentative of the intelligence to be transmitted, means for suppressing saidcarrierffrequency and one of the. side bands produced bysaid modulation from the result, of said modulation, means for radiating the single side band remaining, means for receiving-the energy thus radiated, means forlocally producing-a carrier. frequency current, the

frequency of whichitis desired tocontrol, means for, combining -the, received energy and the 10- cally generatedenergy and thus-producing, the desired signaIsl and a current representative of the transmitted auxiliary current, means for generatingia; 1ocal; auxiliarycurrent, the frequency of; which has a-predeterrnined relationship with ,respectlto the;freq uency of the transmitted auxiliarycurrent, means forcontinuously comparing the'two auxiliary frequencies thus produced, and ,electro-mechanical means; for determining the frequency of thebeatresulting from said comparison, fcontacts adaptedto be'closed by saidlast. mentioned means, a motor, connections forzrotating said motor in. various directions and various speeds in accordance with which of said contacts 2 i, r e closed, means for varying, the

frequency of the-locally generated I carrier; andja I connection whereby 7 said :motor will control. said last neutioned means and thus control the locally generated carrier frequency; to be substantially the same asthatrof the suppressed carrier freill-Q1 63 current atthe transmitter. r 1 7.;Apparatusiforsingleside bandtransmission and reception which comprises means for ,gen-

erating; ;acarrier frequency current, means for generating an auxiliary;, frequency current, the frequency of which is above audibilitmmeans for continuously modulating, the carrier frequency current :by the auxiliary frequency current thus including in the transmission of the transmitter aside frequency representative of saidlauxiliary 'frequencycurrent; means for-generating a current iof an auxiliary frequency at the receiver i having a normallysmall' difierence frequency with respect to the frequency ofthe auxiliarycurrent at the transmitter, meansfor generating a current of the. carrier frequency, the frequency of V which it is' desired to control, 'means for-receivingthe transmitted side band, mea nsfor detectingsaidside bandby the useofsaid locally generated carrierfrequency current, means forlseparatin'g from the product ofsaid detection; the auxiliarycurrent representative of the auxiliary modulating-current atthe transmitter,

means forcontinuouslybeating the frequency of theauxiliaryfcurrentj as thus detected andthe' 4 locally generated'lenergy toproduceja beat, fre- 6 V quency, means to transform the beat frequency energy into corresponding frequency mechanical vibrations, and'means'for' controlling the fre-' quency of the locallygenerated carrier frequency current inaccordance withthe frequency of the produced vibrations, whereby the frequency of said locally generated carrier frequency current is maintained substantiallyfthe same as that of the suppressedcarrier frequency current at the I transmitter. .-l .l v

V 8. Apparatus for single side band transmission I and receptionwhich comprises means for genervibrations, and means for controlling the fre-. quency of the'locally generated carrier frequencyating at the transmittera current of an auxiliary frequency'above good audibility, means for continuously modulating the carrier frequency current by the auxiliary frequency current'thus including in the transmission of said transmitter a side frequency representative of said auxiliary frequency current, means for generating, at the receiver a current having'a'normallysmall difference frequency with respect to the "frequency ofthe said auxiliary; current at'the transmitter,

means for receiving the transmittedside band, a

detector for detecting said side band, means for separating the product of said detection} to sepa-- rate outthe'high auxiliary current representative of the auxiliary modulating current at the transmitter, means for continuously comparing the frequency of the auxiliary-current a's 'thus detected, and that locally generated and producing therefrom a beat frequency; means for changing the beat frequency energy into correspond ing frequency mechanicalvibrations, means-for controlling the frequency of the locally'generated carrier frequencycurrent in" accordance" with the frequency ofthe mechanical vibrations, whereby the frequency of said locally -g'enerated carrier frequency current ismaintained;substantially the same as Y that of thesuppressed carrier frequency current at the transmitter, 1

9; Apparatus-for single side band the suppressed carrier frequency current at the transmitter, which comprisesmeans forcontinuously including in the transmission of the transmitter aside frequency represenative' ofa high auxiliary frequency, at the receiver means for.

generating a current of a-secondhigh auxiliary frequency having a normally small 'difference frequency withrespect to'the frequency of said" auxiliary frequency current at the transmitter;

means for receiving said high auxiliary frequency current at the receiver, means for con- 'tinuouslyfconiparing the frequencyof the auxiliary current thus received and that locally generated and producing beat frequency mechanical current in accordance with thefrequency of the V mechanical vibrations, whereby the frequency of said locally generated carrier frequency current is maintained substantiallyjthe same as that of thesuppressed carrier frequency current at the transmitter. r

10. Apparatus for secret singlesidev band trans- 7 mission and-reception which comprises means for generating a carrier frequency-'current,'- means for wobbling the frequency of said carrier frequency current, means for generating a current of an" auxiliary frequency above good audibility, means for, modulating the carrier frequency current by said auxiliary frequency current and thus in-f eluding in the transmission of transmitter transmission 7 and reception includingapparatusfor controlling the frequency of the-local heterodyne generator at the-receiver to correspond to the frequency'of the side frequency representativeof the said auxiliary frequency, at the receiver means for. generating a current of an auxiliary frequency having anormally small difference frequency with respect tothe frequency of the auxiliary current at thesaid transmitter, means for generating acurrentof the carrier frequency, the frequency-of quency of the auxiliary current as thus detected and that locally generatedto produce electrical energy of beat frequency, a resonator system havingJmeans for resonating at different predetermined frequencies, means controlled by said beat frequency energy for controlling the frequency. 7

at which the resonator operates, and means for controlling the frequency generated by the local 7 carrier frequency generator in accordance with the operation of the resonator, whereby-the frequency of said locally generated carrier frequency current is maintained substantially the same as that of'the suppressed carrier at the transmitter. 11. Apparatus for secret single side band transmission and reception which includes means for generating a carrier frequency. current, means forwobblingthe frequency of said carrier current; means for modulating the carrier frequency current'by a high auxiliary frequency current, and thus including in the'transmission of said transmitter a side frequency representative of said auxiliary frequency; means for generating at the receiver a current of an auxiliary. frequency having a normally small difierence fre- Y quency with respect to the frequency of the auxiliary current 'at the transmitter, means for generating a current of the carrier frequency,

the frequency of which it is desired to' control,

means for wobbling the frequency of said locallyv generated carrier'frequency current to correspond' substantially to the Wobble of said carrier at the transmitter, meansfor receiving and detecting the high, auxiliary current representative of the auxiliary modulating current at the transmitter, means for combining the frequency of the auxiliary current as thus detected and that local- .ly generated to produce a beat frequency, a variablemechanical resonator system adapted'to be controlled by the energy of beat frequency, and

means-for controlling the frequency of the local- V ly generated carrier frequencyin'accordance with the operation of said resonator whereby the frequency of saidlocally generated carrier is main- 'tained in substantially the-same as that of the suppressed carrier of the'transmitter. I

12. Apparatus for secret single side band transmission and reception which includes means for sentative of the intelligenceto be transmitted, means for wobbling the frequency -of-'said side band, means for including in said side band a side frequency representative' of a' high frequency auxiliary current, means for receiving the side band thus transmitted, a local heterodyne generator at-the receiver, means for Wobbling the frequency of'said heterodyne generator to correspond to 1 the' wobbleof a the radiated side band,

producing and radiating a single side band repre auxiliary current representative of the auxiliary currentat thetransmitter, means for combining this latter current with the locally generated auxiliary current to produce a beat frequency; a

mechanical resonator device for controlling the frequency of the local heterodyne, said'mechanical resonator being controlled by the beat frequency energy. v v

13. Apparatus forthe secret transmissionand reception of radiant energyby a wobbled carrier frequency suppression system which comprises means for radiating a'wobbled side band, and ine cluding therein in addition to the'frequencies representative of: the intelligence to be trans mitted a frequency representative of a fixed auxiliary frequencycurrent and at the receiver means forgenerating asecond fixed auxiliary frequency current having a predetermined frequencyrela-V tionship with respect to said first mentioned auxiliary current, means for detecting, the audio frequency current thus transmittedand means for beating said last mentioned 7 frequency with the locally generated auxiliary current, *and means for controllingby the resultantbeat frequency energy themean,frequency'ofthewobbled i v H 1 local heterodyne currentused in the detection of V saidcurrent'as well as in the detection offlthe audiofrequency current representative of the intelligence to be transmitted, said last named ;m eans including a multi-frequency mechanical resonator'device.

14. Apparatus for controlling thelocal carrier frequency generatorat a receiveradapted to receive radiant intelligence transmitted bythe suppressedicarrier frequency. method which comprises means for continuouslyimpressing upon the transmitted energy a constant auxiliary frequency, means at the receiver for. producing a dif-' ferent constant auxiliary frequency, means for comparing the received and locally generated auxiliary frequency and producing a difi'erence frequency, electro-mechanical means actuated by said differencefrequency, additional electro-mechanicalmeans actuated by higher and lower difierence frequencies, a'motoncontacts adapted to be closed by said electro-mechanical means, means for" controlling the frequency, of'the local carrier frequency generator adapted to be operated by said motor, and connections whereby,

closure of various of said contacts. will actuate said motor in such a manner; as to cause the locally generated carrier frequency to correspond to the suppressed; carrier frequency within small degree of variation. V I g ELLISON s. PURINGTO-N. V

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