US2510338A - Means for and method of scrambling speech signals - Google Patents

Means for and method of scrambling speech signals Download PDF

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Publication number
US2510338A
US2510338A US695030A US69503046A US2510338A US 2510338 A US2510338 A US 2510338A US 695030 A US695030 A US 695030A US 69503046 A US69503046 A US 69503046A US 2510338 A US2510338 A US 2510338A
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frequency
bands
band
sub
speech
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US695030A
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English (en)
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Guanella Gustav
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Radio Patents Corp
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Radio Patents Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication
    • H04K1/04—Secret communication by frequency scrambling, i.e. by transposing or inverting parts of the frequency band or by inverting the whole band

Definitions

  • the frequencies of one or more subbands may be inverted by known means to increase the degree of secrecy obtained.
  • the present invention also relates to a scrambling method of this general type known as frequency substitution scrambling, and has for its main object to further increase the degree of secrecy obtained and to substantially prevent the deciphering or decoding of a scrambled message by an unauthorized listener or receiver.
  • the invention involves basically the subdivision of a given signal frequency band, such as a speech frequency band, into a plurality of sub-bands which are mutually interchanged in accordance with the substitution scrambling method.
  • the thus obtained scrambled frequency band is divided into at least two secondary or partial frequency ranges which are mutually interchanged and at least one of which may be inverted, said secondary frequency ranges being so related to the primary scrambling sub-bands that their common limit or separating frequency or frequencies coincide with a frequency within one of said sub-bands.
  • the limit or separating frequency of the partial ranges should not coincide with any of the limit frequencies of the primary scrambling sub-bands, as will become further evident from the following.
  • Fig. 1 is a theoretical diagram illustrating the successive steps of converting a given speech frequency band into a final scrambled band in accordance with the invention.
  • Fig. 2 shows a practical system in block diagram form for carrying into effect the scrambling method illustrated in Fig. 1.
  • Figs. 3 and 4 are partial diagrams illustrating
  • an original speech frequency band a covering a range from 300 cycles to 2,700 cycles, which has been found in practice to be fully sufcient' for the transmission of intelligible speech, is at first transposed or shifted to the range between 8,300 and 10,700 cycles by modulating it in the modulator M1, Fig. 2, upon an auxiliary displacement carrier oscillation u1 supplied by a multi-frequency or harmonic generator G and having a frequency f,1 8,000 cycles.
  • band pass lter F1 the upper side band from the output of modulator M1
  • the frequency band b is obtained in a manner well understood.
  • Filters F2 and F3 may be band-pass or low-pass and highpass lters, respectively, of known design, as is readily understood. 4An essential requirement to obtain a high degree of secrecy is the fact that within each of the frequency bands c1, c2 c6 there exists a different ratio between the partial ranges produced in accordance with the above. In other Words, the individual frequency bands c1, c2 .ce is displaced periodically relative to the fixed frequency t in the manner clearly seen from the drawing.
  • The' resulting lower and accordingly Vinyerted side bands obtained from this modulation are seg-f regated by means of a band-pass filter F4.
  • the partial ranges or 'primary sub-bands .of higher frequency of the speech frequency bands ci', jcz ce are again inter- Vno ulated the :modulator Mtv-lith the respectite aukiliary'os'cillations "us, '1 4 L. u8 and the upper side bands' ofthe'modulation product also segregated by the band-pass filter F4.
  • subba-'nd portion g4 is uninverted, While sub-band ponticn fyi jisvigxryerted and contains the lowest q ,i equencies of the original speech frequnecy band g.
  • An essential condition for the attainment of crecyV is the fact that the lowest s which are predominantly e intelligibility of speech are always cohtainedin the sub-band portion g4 of only i200 cycles band Width.
  • the various elements and parts required for carrying the invention into effect may be of standard design and construction well known in the art. This applies especially to the lters and amplifiers, all of which are common and standard equipment in communication systems.
  • the multi-frequency generator -G may also be of any known construction.
  • a suitable form of such generator is shown in Fig. 3, comprising a tuning fork Oscillator O feeding a harmonic generator A3 in the form of a vacuum tube amplifier designed and operated to produce a highly distorted output wave form, such as by the provision ofa high negative grid bias, as indicated in the drawing.
  • the auxiliary frequencies u1, u2 us are derived from the harmonic spectrum in the anode current.
  • the various modulators used for shifting or transposing the frequency bands to desired points on the frequency scale ⁇ may also be of any type known'in the art.
  • LA system for secret transmission of speech comprising means for sequentially and periodically producing from an original speech frequency band a plurality of equal components eachl displaced Awith respect to the next one by equal frequency ranges being a fraction of the total band width of one over the number of components produced, means for splitting of said components into two partial frequency ranges atv a common andY xed separting frequency, furtherpmeans for shifting the respective partial ranges into a common frequency range of band width' :equal *to the;v original speech n frequency bandfandwith'one of said partial frequency ranges" being inverted, to produce a plurality of pre-scrambled frequency bands comprising par-lk tial ranges of varying relative width, means for,
  • band-pass filter means for segregating from said last-mentioned component equal bands of limited width equal to the above-mentioned fraction of the total original frequency band and having upper and'lower limit frequencies lying at both sides of said separating frequency, and means for unequally shifting the bands selected by said filter meansto positions so as to adjoin each otherand toA form a final scrambled signal of band widthl equalto the original speech frequency band.
  • a system for secret transmission of speech comprising means for sequentially and periodi ⁇ cally producing from an original speech frequency band-a plurality of equal components each displaced with respect to the next one by equal frequency ranges being a fraction of the total band- Width ofA one over the number of components *L produced, means forsplitting of said components into Vtwo partial frequency ranges at a common and fixed separating frequency, further means for shifting the respectivepartial ranges into a.V
  • 3. ⁇ A system for secret transmission of speech comprising means for sequentially and periodically producing from an original speechA frequency band a plurality of equal components each displaced with respect to the next one by equal frequency ranges being a fraction of the total band width of one over the number of components produced, means for splitting of said components into two partial frequency ranges at a common and fixed separating frequency, further means for shifting the respective partial ranges into a ⁇ common frequency range of band width equal to the original speech frequency band and with one of said partial frequency ⁇ ranges being inverted, to produce a plurality of ⁇ sequential prescrambled frequency bands comprising partialI ranges of varying relative width, means for in turn producing from each Vof said pre-scrambled frequency bands a plurality of relatively displaced components coinciding respectively with said first-mentioned components, band-pass filter means for segregating from said last-mentioned components equal bands of limited width equal to the.
  • a system for secret transmission of speech comprising scrambling means for subdividing a given speech frequency band into a pair of primary sub-bands, means for frequency inverting one of said sub-bands, means for sequentially and periodically varying the relative band Width of said primary sub-bands further means for additionally dividing the pre-scrambled frequency band into a number greater than two of secondary frequency sub-bands the limit frequencies of which coincide with diierent intermediate frequencies of said primary sub-bands, means for frequency inverting part of said secondary frequency bands, further means for sequentially and periodically varying the relative band width of said primary sub-bands, and means operated in synchronism with said last mentioned means for varying the interchanging code of said secondary sub-bands.
  • the method of secret signalling consisting in subdividing, by sequential steps of frequency substitution scrambling, a given signal frequency band into groups of different numbers of partially inverted frequency sub-bands, the limit frequencies of the sub-bands resulting from one scrambling step coinciding with intermediate frequencies of the sub-bands resulting from another scrambling step.
  • a system for secret transmission of speech comprising scrambling means for subdividing a given speech frequency band into a pair of primary sub-bands, means for frequency inverting one of said sub-bands, further means for additionally dividing the pre-scrambled frequency band into a number greater than two of partially inverted secondary frequency sub-bands, means for sequentially and periodically varying the relative band width of said primary frequency subbands whereby the separating frequency of said primary sub-bands successively coincides with the center frequencies of different secondary subbands, and further means operated in synchronism with said last-mentioned means for varying the interchanging code of said secondary sub-bands.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
US695030A 1945-09-15 1946-09-05 Means for and method of scrambling speech signals Expired - Lifetime US2510338A (en)

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CH2510338X 1945-09-15

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4058677A (en) * 1974-04-26 1977-11-15 Lear Siegler, Inc. Sound scrambling equipment
US4156107A (en) * 1978-02-03 1979-05-22 Bell Telephone Laboratories, Incorporated Speech signal scrambler
US4179657A (en) * 1958-08-28 1979-12-18 The United States Of America As Represented By The Secretary Of The Air Force Anti-jamming communication system
US4184117A (en) * 1956-04-16 1980-01-15 The United States Of America As Represented By The Secretary Of The Army Communication security method and system
US4188506A (en) * 1973-07-02 1980-02-12 Gretag Aktiengesellschaft Method and installation for masked speech transmission over a telephone channel
US4591673A (en) * 1982-05-10 1986-05-27 Lee Lin Shan Frequency or time domain speech scrambling technique and system which does not require any frame synchronization
US5949878A (en) * 1996-06-28 1999-09-07 Transcrypt International, Inc. Method and apparatus for providing voice privacy in electronic communication systems

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1196713B (de) * 1962-08-30 1965-07-15 Deutsche Bundespost Verfahren zur Sprachverschluesselung
DE2523828C2 (de) * 1975-05-30 1982-08-12 TE KA DE Felten & Guilleaume Fernmeldeanlagen GmbH, 8500 Nürnberg Verfahren zur Verschleierung von Sprachsignalen mit Hilfe orthogonaler Matrizen

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1725566A (en) * 1927-12-15 1929-08-20 Bell Telephone Labor Inc Secret communication system
US2301455A (en) * 1939-10-27 1942-11-10 Wireless Res Corp Apparatus and method for communication
US2402059A (en) * 1942-04-29 1946-06-11 Hazeltine Research Inc Secrecy communication system
US2411206A (en) * 1943-04-05 1946-11-19 Radio Patents Corp Electrical signaling method
US2411683A (en) * 1943-06-23 1946-11-26 Radio Patents Corp Method and arrangement for scrambling speech signals

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1725566A (en) * 1927-12-15 1929-08-20 Bell Telephone Labor Inc Secret communication system
US2301455A (en) * 1939-10-27 1942-11-10 Wireless Res Corp Apparatus and method for communication
US2402059A (en) * 1942-04-29 1946-06-11 Hazeltine Research Inc Secrecy communication system
US2411206A (en) * 1943-04-05 1946-11-19 Radio Patents Corp Electrical signaling method
US2411683A (en) * 1943-06-23 1946-11-26 Radio Patents Corp Method and arrangement for scrambling speech signals

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4184117A (en) * 1956-04-16 1980-01-15 The United States Of America As Represented By The Secretary Of The Army Communication security method and system
US4179657A (en) * 1958-08-28 1979-12-18 The United States Of America As Represented By The Secretary Of The Air Force Anti-jamming communication system
US4188506A (en) * 1973-07-02 1980-02-12 Gretag Aktiengesellschaft Method and installation for masked speech transmission over a telephone channel
US4058677A (en) * 1974-04-26 1977-11-15 Lear Siegler, Inc. Sound scrambling equipment
US4156107A (en) * 1978-02-03 1979-05-22 Bell Telephone Laboratories, Incorporated Speech signal scrambler
US4591673A (en) * 1982-05-10 1986-05-27 Lee Lin Shan Frequency or time domain speech scrambling technique and system which does not require any frame synchronization
US5949878A (en) * 1996-06-28 1999-09-07 Transcrypt International, Inc. Method and apparatus for providing voice privacy in electronic communication systems

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CH246844A (de) 1947-01-31

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