US2407308A - Method and apparatus for secret signaling - Google Patents

Description

Sept m, 946- R. LoRENzEN ETAL 2,407,308

METHOD AND APPARATUS FOR SECRET SIGNALING Filed Jan. 1e, 1941 5 sheets-sheet 1 /llo Esse-r" La/zeazsq ATTORN Sept. l0, 1946.

Filed Jan. 1e, '1941 5 Sheets-Sheet 2 Sept. w; 194s.

R. LORENZEN ETAL METHOD AND APPARATUS FOR SECRET` SIGNALING Filed Jan. 16, 1941 5 Sheets-Sheet 3 as se a1 34 AMPLIFIER INTERMEDIATE AMPLIFIER DD# MoDuLAToR MoDuL-ATING MoouLA'roR A oscILLA-roR A A ss do 4I 4e 35 AMPLIFIER INTERMEDIATE AMPLIFIER CARRIER ED- MoDuLAI'oR MoouLATING MoouLAToR FREQUENCY B oscILLAToR e osclLLAToR FI B FC I FC CFIAFSA: 4a 44 4s FctrFxBtl-'SBJ Pci I: FIC-1 Fsc: 42 AMPLIFIER INTERMEDIATE AMPLIFIER DD- MoDuLAroR` MoouLArINs MoouLA'roR C oscILLAToR c 49 `5o 5I s2 sa 54 4s g I e I Q I@ f Vs C *og 9 4"? Qvs R026* Fs F A #s e? 6%* f" Q4. o f* ss 57 sa En so eI ss ftp? e" 50e Q- Q@ Oo Qr .5S ov @Q F O Q v S e9 6' QVQ 9 Q o I B gvc o@ of QWQQ & QQ YF* 9 es e4 es es e7 se A e A0 v E Q- Qs? 09s' i 6 oy' s@ V lIF l QV Y o A@ Q @o `k- Qv o sc '9. Q0 o@ o?. VQQO o@ YQ Q6 INVETFO RBEQTLORENZE' R* Flam); Spia sc ATTORNEY Sepl0, 1946. R. LoRENzl-:N ETAL METHOD AND APPARATUS FOR SECRET SIGNALING Filed Jan. 16, -l94l 5 Sheets-Sheet 4 INVENTOR Egger L WEA/25N ATTORNEY.

Sept., M), w46.

R. LORENZEN ET AL 5 Sheets-Sheet 5 Patented Sept. 10, 1946 METHOD AND APPARATUS ron SECRET SIGNALLNG Robert Lorenzen and Felix Spiegel,

New York, N. Y. Application January 16, 1941, Serial No. 374,790

2 Claims. l

The present invention relates to methods and apparatus for secret signaling.

The disadvantages of present existing communicationg systems are: (l) the possibility of blanketing-out or jamming the audiofrequency signal modulation by a third party, thereby disrupting communication service, and (2) the possibility of a third party intercepting signals that are desired to be kept secret.

The need for new communication systems is to obviate the above mentioned disadvantages and shortcomings of present systems, for the present invention introduces a multiplicity of communication systems which can either be used alternately or in conjunction, whenever the need arises. Thus, if by remote chance one of the hereinafter mentioned systems should fall into the hands of a third party so that this third party discovers the technique employed in the new system, it is merely necessary to adopt one of the manifold alternate systems.

The possibility of employing a multiplicity of alternative communication systems is obviously of considerably greater advantage than would be the case if the number of communication systems were limited to three as at present, for if it is assumed that any one of the multiplicity of the new systems is employed, then any means for blanketing-out or jamming the conventional eX- isting transmissions lwill leave the new system unaffected, despite the fact that the means employed by the third party have electively paralyzed the yconventional existing means of communication. By the employment of the new systems, hereinafter to be described, the desired communication is enabled to be continued without interruption or interference.

One of the objects of this invention is to show how an innitely large number of diierent communication systems are made available instead f merely the present limited number of available systems, namely, three.

Another object of the present invention is to show how uninterrupted communication may be maintained between two parties, despite the fact that a third part may, by the process of creating artificial noise and interference, cause the iamming of conventional communication systems so as to result in a complete disruption of communication service.

Still another 'object `of this invention shows how it i-s possible to maintain uninterrupted communication between two parties even though some third party has discovered the principle of ysystems which employ ultra-audible waves in a Imaterial medium as a means of c-ommunication. Stil1 another object of the present invention isV to show how the herein described principle may be applied to communication systems which employ electromagnetic waves of a non-radio character as the carrier of the transmitted signals. Typical of such systems are those which utilize a light-beam as the means of transmission, or infra-red rays as the carrier of the transmitted signals, or ultra-violet as the signal carrier.

Another object of the invention is to show the application of the present system to those communication systems which employ wired wireless, i. e., where the signals are transmitted along either a conductor or a dielectric guide.

Another principal object of the present invention is the simultaneous transmission of different signals when but. a single carrier frequency is employed.

Still another object of the invention is the simultaneous transmission of the desired signals and false signals, soI that, although only the desired signals are received by the two parties between whom communication is established, any outside third party receives only the false signals and is thereby deceived as to the real content of the transmitted messages.

Still another object of the invention concerns itself with a new method of scrambling signals so as to make the interception of transmitted messages impossible to any outside third party who is not informed both as to the method of scrambling and the principles underlying these new communication systems.

The present invention will be described Iwith reference to the accompanying drawings, but it will be realized that other application-5 and embodiments lie within the scope of the invention, for it should be understood that the scope of the present invention is so broad that only the general features are herein disclosed. Subsequent patent applications will describe the various specic embodiments and give in more concrete form the manifold applications and modifications of the principle herein described.

Fig. 1A represents the generalized set-up of a through space, this, in turn,

transmitter which employs multiple modulation,l

Fig. 4A represents a transmitter whichV is capable of transmitting both the desired as wellV assv false signals, while Fig. 4B represents a receiver for receiving the desired signals.

Fig. A represents a transmitter employing triple modulation in which the signals are scrambled in such a manner that part of .the scrambled signals modulate the first intermediate-modulating frequency and the otherpart of the scrambled signals modulate-the secondintermediate-modulating frequency. Fig. 5B represents a receiver for the reception of such scrambled transmission.

In the conventional communications system,.at the transmitter a signal frequency modulates a carrier frequency, this latter being propagated is received at areceiver, Where, after' suitable demodulation, the original signal frequency is obtained. AsY will hereinafter be disclosed, the present conventional method is but a very special case of the new general principle, which concerns itself with means and methods superimposed and multiple modulation of signals. In order to reduce the complexity of description,

the principles underlying multiple modulation Again, although later descriptions will utilize various combinations of amplitude, frequency, and phase modulation, further simplicity of description will at this time be secured by making the two following assumptions: (1). amplitude modulation is employed throughout, and (2) spurious modulation products are disregarded. In addition, although it will shortly be seen that the new principle is will first be discussed.

-applicable .to other than itsemployment'in radio :i

transmission and reception, the preliminary description will restrict itself to its application to radio communication.

Referring to Fig. 1A, which represents in block diagram form a transnriitterv employing multiple modulation, I represents either a source or pickup of the signals fs. Signals from l go to the amplier-modulator 2', the output of which is employed to modulate an oscillator 3 which isv oscillating at the frequency fn. Oscillator 3, which shall be called the first intermediate-frequency oscillator produces an oscillation which is some multiple, not necessarily integral, of thefrequency of the signal frequency. If the signal is comprised of a band of frequencies, as would be the case when the signal consists of speech or music, the rst intermediate frequency oscillator will have a frequency which is some multiple of. the highest signal frequency. The output of intermediate frequency oscillator 3'feeds into the input of the amplifier-modulator 4, where the signal-modulated fn frequency is amplified and then employed to modulate the second intermediate frequency oscillator 5, whose oscillation frequency fi2 is Ysome multiple of, that of the for producing andY utilizingV frequency remains, this into a,V radiatorY Il), which in 4 rst intermediate oscillation frequency fn. The foregoing process continues, as indicated by the dashed lines, until the multiply-modulated resulting signal is fed into .the amplifier-modulator 6, the output of which is employed to modulate the nth intermediate frequency oscillator l, whose oscillation frequency fin is some multiple of the (n-Dth intermediate frequency oscillator. The output of the nth intermediate frequency oscillator 1 goes to an amplifier-modulator 8, which is employed to modulate the carrier frequency oscillator 9. The modulated outputofthe carrier frequency oscillator 9 is then either directly, or after further amplification, fed the case of radio transmission would consist of an antenna system,

At the receiving station, as illustrated in Fig. 1B, the multiply-modulated signal is picked up by antennai t which is connected to amplifier i2. This amplifier i2 is capable of amplifying the carrier frequency and should have an amplifying bandwidth capable of amplifying the accompanying multiply-modulated signal. After suitable amplification.V by amplifier l2. the signal is fed to demodulator i3, which removes the carrierI frequency fc and leaves only the multiply-modulated signal jin. The output of demodulator I3 goes to amplifier if, which amplifies the signal at frequency jim and which possesses a band-width capable of amplifying the accompanying multiple modulation. The output of amplifier I4 goes to demodulator l5 which removes the nth intermediate modulating frequency, so that the output of demodulator ifa-consists of the multiplymodulated @L -1) th intermediate modulating frequency. This signal is fed to amplifier ing frequency` and which has an amplifying bandwidth suitable for amplifying the accompanying multiply-modulated signal. This process is repeated, as indicated by the dashed lilies, until only thev multiply-modulated second intermediate being amplified by amplifier il, after which it is fed to demodulator I8; Demodulator iremoves the second'intermediatemodulating frequency, thereby leaving only the signal-modulated first intermediate-inodulatingA frequency, Tlieoutput of demodulator iS goes to amplifier lil, which is capa-ble of amplifying the first intermediate-modulating frequency and its accompanying signal modulations. The output of amplifier IS goesto demodulator 20 which removes the first intermediate-modulating frequency and leaves only the original signal frequency.

rihe output of demodulator 20 then goes to amplifier 2l which ampliiies theV original signal frequency. After sufficient amplification the'original signal frequency may be taken from the output of amplifier 2l to actuate any suitable device, such as, for example a loudspeaker or telephone receiver.

Having explained the general principle of multiple modulation, there will now be considered a simple, example of multiple modulation, namely, when only a single intermediate modulating frequency is employed. The symbol fs willv be used. to designate the signal frequency, which, for co ivenience, may consisty of those frequencies of which music or speech sounds are comprised. The symbol fr will be used to represent the intermediate modulating frequency, which, in this case, we may assume to be a fixed frequency of 100,000 cycles. Similarly, the symbolfcshall be used to designate theV carrier frequency, which, in this I6, which. ampliiies at the ('n-Dth intermediate modulatcase, should preferably be greater than one megacycle.

Referring to Fig. 2A, which shows a block diagram of the transmitter, the microphone 22 picks up the speech sounds which it is desired to transmit. The microphone connects to the amplifiermodulator 23, which rst suitably amplies the signal frequency and then is employed to modulate the intermediate-modulating frequency fr produced by the intermediate-frequency oscillator 24. In consequence, the resulting output is comprised of the intermediate modulating frequency fr in conjunction with the sum and difference sideband frequencies due to the signal frequency fs. This resulting output then goes to the amplifier-modulator 25, where, after suitable amplification, it is used to modulate the carrier frequency oscillator 2B which is oscillating at a frequency fc. As a result there is obtained an output which is comprised of the carrier frequency in combination with the sum and difference sideband frequencies due to the complex of the signal frequency and the intermediate-modulating frequency. After suitable amplification, if desired, the doubly modulated carrier is radiated into space by means of the antenna 21.

At the receiver, as shown in Fig. 2B, the doublymodulated carrier impinges upon antenna 28 and is then amplified by amplifier 29. The output of amplifier 2S consists of the doubly-modulated carrier frequency and this is fed to the demodulator 30 which removes the carrier frequency and leaves only the signal-modulated intermediatemodulating frequency. This, in turn, is amplified by amplifier 3| and is then fed to the demodulator 32 which removes the intermediatemodulating frequency and leaves only the original signal frequency fs. After suitable amplification by means of amplifier 33 the resulting signal frequency may be used to actuate a loudspeaker.

It is therefore seen that even when using such a simple set-up as the one just described, a considerable degree of secrecy of message communication may be obtained. For, if in the attempt to intercept a message from the transmitter of Fig. 2B, an ordinary receiver were tuned to the carrier frequency fc, nothing would be heard for the resulting demodulated frequency would be the intermediate-modulating frequency fr, and since this was chosen to be about 100,000 cycles it is beyond the audible frequency range and would not, therefore, be heard. Only a receiver which doubly demodulates the doubly-modulated carrier would be capable of properly receiving the transmitted message.

In a similar manner, two intermediate-modulating frequencies may be employed to obtain a triply-modulated carrier, thereby making it still more dicult for the uninformed to intercept the transmitted message. It is unnecessary to describe such a system at this point, as this type will later be used when the description of superimposed modulation as used in conjunction with multiple modulation is described.

At this point it will be well to examine the number of different communication systems which are possible as a result of the employment of multiple modulation.

When only one intermediate modulating frequency is employed it will be seen that: (1) The signals may modulate the intermediate-modulating frequency by means either of amplitude, frequency, or phase modulation, and (2) the intermediate-modulating frequency can modulate the.

6 carrier frequency by either amplitude, frequency, or phase modulation. Under these conditions the number of permutations is nine, so that nine different communication systems result. This mayV be seen from the following table.

I Method by sgr which intermemodulate g. diete-modulaff s Inter ing frequency lgliegle'nlllgl' modulates the g eq y carrier frequency Amllilitude IAmplitude o. requency Do. Phase Frequency mplitude v O. IeqlleIlCy Do. Phase Phase Amplitude Do. Frequency L Do. Phase twenty-seven, it is seen that twenty-seven different possible communication systems are possible when two intermediate modulating frequencies are utilized. v

Similarly, when three intermediate-modulating frequencies are employed, the resulting number of different communication systems is eightyone.

In general, when n intermediate-modulating frequencies are employed the resulting number of different communication systems is 30H1).

Since all of these different systems may be t simultaneously employed, the total number N of different communication systems, and including the conventional single modulation, which result is given by the expression N=31+32+33+341 3(1L-l-l) where n represents the number of intermediatemodulating frequencies. It is readily seen, therefore, that the number of different communication systems which become available increases very rapidly as the number of intermediatemodulating frequencies is increased. The rapidity with which different communication systems become available is shown by the following chart.

Number of Number of intermediateavailable commodulating munication frequencies systems 0 3 1 12 2 39 3 120 4 363 5 1, 092 ad infinitum ad infinitum of indefinite extensionr there are, nevertheless,

practical limitations. Which..mitigate against such indefinite extension. This practical limitation is dependent upon the amountv of frequency bandwidth available, for, asthenumber ofV intermediate modulating frequencies areiincreased, so, likewise, is the necessity for an increased frequency band-width. Consequently, as more and more intermediate-modulating frequencies are employed the higher must the frequency of the carrier become: in. order to maintain the frequency band-width required at some given percentage of the carrier frequency.

The intermediate-modulating frequency f1 is not restricted toV any single frequency and may assume various values, such as ffl, frz, frs, etc. for anygiven carrier frequency f,.the same (or different) station may employy the intermediate-modulating frequenciesfrl, frz, T13, etc., to modulate the carrier. Since, in this event, bandpass filters would be employed .to prevent any interaction or interference. of the various intermediate-modulating frequencies, it is seen that the-simultaneous transmission of diverse signals may be transmittedand received although but a single given carrier frequency is employed.

A typicalV example.V of a transmitter which enables the simultaneoustransmission of different signals when. but a single` carrier frequency is employed is illustrated. in Fig. 3A. For simplicity of description only one intermediate-modulating frequency is used, as the extension of the-method.

so asi to employ twoor. more intermediate-modulating, frequencies is` obvious. The microphone 34 picks up the speechV` signals. fs. at point A and these are fed to the amplifier-modulator 35. The intermediate-modulating oscillator 36, whose oscillation frequency fm may, for example, be

100,000 cycles, is modulated by amplifier-modu-` lator 35. This modulated output then goes to amplifier-modulator 31, which', in turn, modulates the-carrier frequency oscillator't. The doublymodulatedwaveis thenfedinto the' antenna 41.

In a similar manner, microphone 33- picks up the speech signals fsB at point B and are then suitably amplified` by means of amplifier-modulator 39. The intermediate-modulating oscillator has a frequency fm which is different from that of intermediate-modulating oscillator 36, and it may be assumed, for example, that the intermediate-modulatingv frequency fm is 200,000 cycles. Amplifier-modulator'then causes thisresulting. signal to` modulate. the' carrier frequency oscillator.y

The microphone 42, the amplifier-modulator 43, the intermediate-modulating oscillator All, and `the amplifier-modulator 45 operate in a similar manner. Again the' frequency fic of intermediate-modulating oscillator Ml is different from that of the intermediate-modulating oscillators 36 and 40, so'that, for example, the oscillation frequency fic of intermediate-modulating oscillator 44 may be. 300,000 cycles.

It is, of course,.not necessary that the single carrier frequency oscillator 43 be employed. Instead, separate carrier frequency oscillators may be used; the carrier frequencies of the separate oscillators being the same ordierent'as desired.

Returning tothe preceding case, the complex of Waves radiated by transmitting antenna. 41 arepicked upby antennas d'8, 55, and 62 of`Fig.

3B; Considering. the first ofi these receivers, antenna 43 connects to amplifier 49 which amplifies the carrier frequency. Afterv suitable amplification the complex signal is demodulated by demodulator` thereby eliminating the carrier.' The: output' of the demodulator willi contain all of the intermediate-modulating frequencies and' their accompanying modulations. Accordingly; a band-pass-lter 5i isinserted-in the output circuit. of demodulator 50. This band-pass lt'er should beV operative at frequency fm, namely, at the frequency of the intermediate-modulating oscillator 361 of thetransmitter, and' it should have a' pass-band suflifciently Wide as to pass' the origiinal` signals of frequency tenuation. The output ofthe band-passfilter Will' then contain intermediate-modulatingi frequency fmwhich has been modulated by the original signal frequency fsa. This is-thenamplied' by amplifier 52- and then demod'ulated by demodulator 534 so that the intermediate-modulating frequency fla is removed. The remaining signalv frequency fs. is thenA amplified by amplifier Sli, the output of whichY goes to` any suitableI device, as for example, a loud speaker or ear phones;

The operation cf the second receiver is similar to that just described. Antenna receivesthe complex of signals radiated by transmitting antenna 41 and this is fed tothe amplifier 56- which amplifies at the carrier frequency, after which demodulator 51 removes the carrierY frequency. Since in this case it is desired'Y to receive the signal frequency fsa the band-pass filter-5B' operates at' frequency fm corresponding to frequency fm of' oscillator 40 in thetransmitter.

Itis now possibleto' examine how this'neW communication system may be utilized so that the regular transmission ofv unimportant signals which employv the customary direct modulation may be simultaneously transmitted in conjunction with multiply-modulated signals containing the essential information, in order to deceive any third party who may the attempt' to intercept. the desired signals'. Atypical transmitter' for. performing. this function is shown in Fig. 4A. The desired signals fs are picked up by microphone ES', are' amplified' by ampli'er-mod'ulatorv 1D', and' are then employed' to modulate theintermediate-modulating frequency oscillator 1|'. The frequency of' oscillation fr of the intermediatemodulating frequency oscillator 1|' may be any suitable value, as. for example, 100,000 cycles..

The' modulated' output of intermediate-modulat'- ing frequency oscillator 1'I is fed'to' the. amplifiermodulator 12, which latter is used" to modulate the-carrierfrequency oscillator 13, and these signals are radiated' into" space via antenna 16. Simultaneously with the' preceding, the falsesignals Fs are rpicked'up by microphone 14', are amplified bythe amplifier-modulator 15*y which latter also modulates the` carrier frequency oscillator 1.3',-

. after which these false signals are. also radiated int'osp'ace via the antenna 161.

It is therefore seen thatthe radiati'ons'emanatingfrorrrantenna'16` consist ofthe' desired' signals andJ the; false signals;

ff.- Will receive only the false signals since itwill be unresponsive tov the intermediate-modulating frequency fr.'

In" order. to 'receive' the, desired signals Yav receiver of the type shown in FigAB may be employed. Antenna 11 picks up the signal" radiated from antenna 16'.

fsA without undue' at- Y A conventional receiver' which is tuned to` receive the carrier frequency This doubly-modulatecl signal is amplified by amplifier 78. The demodulator 79 removes the carrier frequency so that the output of demodulator 'I9 contains the desired signalmodulated intermediate-modulating frequency and the false signals. The band-pass filter 89 permits only the signal-modulated intermediatemodulating frequency to pass through, so that the output of band-pass filter Gi does not contain the false signals. After further amplification by means of amplifier SI the signal-modulated intermediate-modulating frequency goes to demodulator 82 which removes the intermediate-modulating frequency and leaves only the original desired signals. After further amplification by amplier 89 the desired signals may be utilized to actuate any suitable device, as, for example, a loudspeaker or earphones.

rihe signaling system just described is not limited merely to the use of a single intermediatemodulating frequency, but may employ multiplef modulation using any number of intermediatemodulating frequencies, as desired.

There will now be described a typical method whereby the desired signals are scrambled so that the separately scrambled portions of the scrambled signals modulate difierent intermediatemodulating frequencies. One of the manifold of transmitters for accomplishing this purpose is shown in Fig. A. The desired signal fs is picked up by microphone 34, these signals then being suitably amplified by means of amplifier 85. From here the signals go to a Scrambler 86 which breaks the signals up in any desired manner. One portion of these scrambled signals feeds into the amplifier-modulator 8l while the other portion of these scrambled signals feeds into the amplifiermodulator 89. That portion which Went to amplifier-modulator 81 is utilized to modulate the first intermediate-modulating frequency oscillator 88, the output of which also goes to amplifiermodulator 89. Amplifier-modulator 89 then modulates the second intermediate-modulating frequency oscillator 90. In other Words, the second intermediate-modulating frequency oscillator 90 is modulated both by a portion of the scrambled signals and by the signal-modulated first intermediate-modulating frequency. The output of oscillator 9! consisting of the superimposed modulations then goes to amplifier-modulator 9|, which latter modulates the carrier frequency oscillator 92. After further amplification, if desired, by means of amplifier 93 the scrambled complex of triply-modulated and doubly-modulated Waves are radiated into space by means of antenna 94. Although for the sake of simplicity it has not been shown, it is obvious that the system just described can be used in conjunction With the transmission of false signals.

The reconversion of the original desired signals is accomplished by means of a receiver of the type shown in Fig. 5B. Antenna 95 picks up the compleXly-modulated carrier which is then amplified by means of amplifier 96. The process of demodulation by means of demodulator 91 removes the carrier, the output of the demodulator then going to the descrambler 98. Descrambler 98 is arranged to act in synchronism with the Scrambler 86 of the transmitter, and is so adjusted that the doubly-modulated portion goes to amplifier 99, While the single-modulated portion goes to amplifier IUI. After suitable ampliflcation by means of amplifier 99 the doubly-modulated portion is demodulated by demodulator |09, so that the second intermediate-modulating frequency is removed. The output of demodulator li then goes to amplifier iI, as did also one portion of the desorambled signals coming from descrambler 98. After suitable amplification by amplifier I EI, demodulator IGZ removes the first intermediate-modulating frequency, so that the original signal now appears in the output of the demodulator. After suitable amplification by means of amplifier IGS, the output of this ampliier may be utilized to aetuate any suitable device, such as, for example, a loudspeaker or earphones.

The principle herein described is not limited in its scope merely to radio transmission and reception, for the principle of multiple-modulation may be utilized in conjunction with supersonic signaling, to Wired Wireless, as well as to signaling by means of other non-radio electromagnetic radiations, such as light-beam signaling, infrared signaling, and ultraviolet signaling.

Thus, in supersonic signaling, if IU in Fig. 1A, 27 in Fig. 2A, s1 in Fig. 3A, 'I6 in Fig. 4A, and 94 in Fig. 5A represent supersonic output sources, the transmitters described in these various figures may be employed to transmit multiplymodulated supersonic waves. Similarly, if I I in Fig. 1B, 28 in Fig. 2B, 48, 55, and 62 in Fig. 3B, 'I1 in Fig. 4B, and 95 in Fig. 5B consist of supersonic pickup devices, the various receivers described in these various figures may be employed to receive multiply-modulated supersonic waves.

In a similar manner, a third party who attempted to intercept the signals of multiplymodulated light-beam, infrared beams, or'ultraviolet beams would receive the false transmissions if such were transmitted, but would not, for the reasons already given, be able to intercept the real signals which it Was desired to transmit.

The principle herein described, together with the various systems evolving from this principle is not, of course, limited in scope to the doublesideband transmissions which were used for illustrative purposes only, but may utilize the various other forms of transmission technique as, for example, single-sideband transmission, asymmetric-sideband transmission, suppression of the carrier at the transmitter, as Well as the other transmission techniques known to the art.

We claim:

1. A radio signaling system including a transmitter and a receiver, and in which the transmitter is provided with a pickup device and a carrier frequency oscillator, and interposed modulators and companion oscillators employing amplitude, phase, and frequency modulations; and in which the receiver is provided with a receiving element and a translating device, and interposed modulators and oscillators for receiving from the receiving element such amplitude, phase, and frequency modulations as originated in the transmitter and delivering same to the translating element.

2. A radio signaling system as claimed in claim l, wherein the number of oscillators and their companion amplitude, phase, and frequency modulators are arrangeable in a selected sequence.

ROBERT LORENZEN. FELIX SPIEGEL.

Images