US2530142A - Secret signaling system - Google Patents

Description

Nov. 14, 1950 c. E. ATKlNs SECRET SIGNALING SYSTEM Original Filed Aug. 11, 1944 kai km @SEEE JNVENTOR. C4 RL 50W/wo Anf/Ns 1] Wma/,4M ATTORNEYS Nov. 14, 1950 c. E. ATKINS SECRET SVIGNALINE SYSTEM 2 Sheets-Shet 2 Original Filed Aug. 11, 1944 1%* Wmwmmww A TTORNEYS Patented Nov. 14, 1950 SECRET SIGNALING ASYSTEM VCarl Edward Atkins, Elgin, Ill., vassignor to Tung- Sol Lamp Works, Inc., Newark, N. J., a corpo'- rationof Delaware Original. application August '11, 1944, Serial No. 549,015. Divided and this application February 7, 1950, Serial No. 142,888' Y 2 Clails.

vThis invention relates to secret signaling and constitutes a division of my application for United States patent, Serial No. 549,015, led August 1l, 1944, and entitled Secret Signaling System.

"More particularly, my inVention comprises a system whereby intelligence may be scrambled at one station and transmitted from that station for reception and decoding at `a plurality of other stations withoutdanger of detection by unauthorized interceptors of the transmitted scrambled intelligence. Briefly and in general, the system of the present invention comprises the like treatment at each station of capriciously varying energy available at each station and the subsequent utilization of suchv treated energy for scrambling at the transmitting station the signal to Vbe transmitted and for unscrambling, at the other stations, the received energy. The like treatment'of the varying' energy at each station may be effected in various ways. For example, a suitable capriciously varying signal such as a delayed replica of signal intelligence or noise could be usedV to scramble the signal Vintelligence to be transmitted and received andsuch capriciously varying energy ornoisefmay also be further treated lor modified by a signaluniformly varied in either voltage or frequency. Thus in general secrecy is achieved in the system by like treatment known only to the station concerned of energy which may or may not beVv known to an eavesdropper and theV scrambling of the transmitted signal with such treated energy.

For a better understanding of the invention reference may ber had to the accompanying drawings, of which Fig. 1 is a diagram explanatory of the invention; and Y Fig; 2'is a block diagram illustrating one em-V bodiment thereof.

The term scrambling as'used` herein relates to vfthe'mixing or compounding of an intelligible signal `vvith'other signals to form an unintelligible result for purposes of transmission to another station.

The underlying theory of the system of the invention will best be understood by reference to Fig, 1 which represents diagrammatically the secret transmission of intelligence from a single transmitting station A to each of a plurality of receiving stations B. At station A and at each of stations B there is available capriciously varying energy which may, for example, be that radiated from a separate station C. At station A and also at each of the stations B are like means for treating the energy received from C. Such means may be formal scrambling devices known to the art or other scrambling means hereinafter described may be employed. At station A the capriciously varying energy from source C is first treated by the scrambling means at that station andthen the signal to be transmitted is scrambled with the so treated capriciously varying energy and radiated to the receiving stations. At each station B the capriciously varying energy from station C is received and likewise the radiated mixture, including the signal, is received from station A. As each station B includes a scrambling means identical to that at station A, the capriciously varying energy can be similarly treated-'and the lsignal mixture decoded Aby using the treated capriciously varying energyV for unscrambling the signal'mixture. Thus although an eavesdroppermight pick up the energy radiated from C and also that from station A, he would not-be able to decipher the signal. This is so because in order to get a clue to the deciphering or decoding of a message, an eavesdropper Vdepends upon getting an intelligible result. The energy radiatedl from source Cy contains no signalias it is merely capriciously varying energy. The mixture radiated from station A includes components corresponding to the energy radiated from C, components introduced by the scrambling device'and theactual signal intelligence. If the energies from source C and station A were compared by the eavesdropper, the result, being the signal scrambled by the scrambling device at station A, is not intelligible. However, at the various stations B, the signal can be detected because of the inclusion in the station equipment of scrambling means identical with' that at station A.

In Fig. 1 the sourceC of capriciously varying energy has been indicated as being a separate station transmitting energy to station A and to all stations B. Obviously this source could as well belocatecl at stationA or at any station B.

Fig. 2 illustrates diagrammatically a system embodying the invention. In this figure random noise impulses produced by a noise generator at station A, are used, after formal preparation, to scramble the intelligence transmitted from that station. Key 'I is the source of the signal intelligence to be transmitted and it actuates the main Scrambler or gate 6, passing energy to the main transmitter 8. The output of noise generator 60 is radiated directly by auxiliary transmitter 2. In order that the noise may be used to scramble telegraph signals using gates as instrumentalities, it is necessary to select a certain 3 specific portion of the noise spectrum and prepare it for application to scrambler or "gate 6. Accordingly, energy from noise generator 60 is fed to a scrambler 4a, to which is also applied energy from a variable frequency oscillator 62, the frequency of which is shifted in a predetermined manner by electro-mechanical means 63 activated by a motor 64. Scrambler 4a is any suitable device known in the art for heterodyning the energy received from noise generator 60 with the energy delivered by oscillator 62. The output of Scrambler 4a is fed to a band pass filter 65 which stations. Thus an unauthorized intercepter of the transmitted mixtures can not, from either mixture alone or from both together, determine the communicated intelligence. Various alternative arrangements within the scope of the invention will occur to those skilled inthe art. Preferably, the scrambling and unscrambling means at each of the stations, particularly when the signals to be communicated are telegraphic symbols, are electronic gates but other scrambling means could be employed if desired.

serves to select those frequency components that are within its band at a given time. Energy passing through filter 65 is fed to an amplitude discriminator 66 which selects pulses having an amplitude in excess of a predetermined level, or sufficiently above the average level of the noise energy passing through filter 65. Discriminator 66 could be, for example, a voltage delayed diode circuit such as used as noise limiters in communication receivers. The output of discriminator 66 is fed to an electronic switch 61 which is triggered by the impulses selected by unit 66 on an on-andoff basis. That is, if one impulse turns the switch 61 on, the next impulse turns it off and the next succeeding impulse turns it on again. As electronic switches of this type are knownin the art, further description thereof is deemed unnecessary. The control impulses from the electronic switch 6l are used to scramble the signal intelligence in gate 6.

At station B noise energy transmitted from transmitter 2 of station A is picked up by antenna l2, demodulated in auxiliary receiver I3 and delivered thereby to unscrambler Mia. In -unscrambler Illa the demodulated noise energy is heterodyned with energy from a variable frequency oscillator 68, the frequency of which is varied synchronously with that of oscillator 62 by electromechanical means 69 driven by synchronous mot or 18, motors 64 and 'I8 being synchronously operated by any suitable means and the variations of frequency of oscillator 68 taking place at a slightly later time than the corresponding variations of oscillator 62 in order to compensate for the distance between the stations.

l The heterodyned energy delivered by unscrambler Ilia is treated as is the output of Scrambler la at station A in order to prepare it for application to unscrambler unit I6, that is, it is passed through band pass lter "I9, amplitude discriminator l0 and electronic switch 1I, corresponding respectively to units 65, 66 and 61 of station A. Un-

scrambling gate yIIS activated by the pulses It is also to be understood that the variable sig- V,nal energy produced by the oscillators 62 and 68 and used for treating the noise need not be of a ,l constantly variable frequency but may follow any bling noise energy from said source with said predeterminedly varying energy, means at each station connected to said scrambling device for converting the output thereof into energy impulses,

means at the transmitting station for scrambling signal intelligence with the pulses delivered by said last mentioned means, atransmitter and antenna at the transmitting station for radiating they scrambled signal, means at a receiving station for receiving the scrambled signal transmitted from the transmitting station, an unscrambling device at the receiving station actuated by the impulses delivered by the converting` means at that station and by the received scrambled signal and means associated with said devices for compensatingy for. transit time of said noise energy and of said radiated scrambled signal whereby said last mentioned .device yields the signal introduced at the transmitting station.

2. The system according to claim 1 wherein said source of noise energy is located at the transmitting station and wherein means are provided at such station for transmitting the energy therefrom to the receiving stations for application to the scrambling device at such stations.

CARL EDWARD ATKIN S.

REFERENCES CITED The following references are of record in the.

file of this patent:

UNITED STATES PATENTS 2,476,337 Varian July 19, 1949

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