GB570488A - Improvements in systems for the secret electrical transmission of speech - Google Patents

Improvements in systems for the secret electrical transmission of speech

Info

Publication number
GB570488A
GB570488A GB4286/43A GB428643A GB570488A GB 570488 A GB570488 A GB 570488A GB 4286/43 A GB4286/43 A GB 4286/43A GB 428643 A GB428643 A GB 428643A GB 570488 A GB570488 A GB 570488A
Authority
GB
United Kingdom
Prior art keywords
sub
bands
speech
frequency
attenuators
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB4286/43A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Patelhold Patenverwertungs and Elektro-Holding AG
Original Assignee
Patelhold Patenverwertungs and Elektro-Holding AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Patelhold Patenverwertungs and Elektro-Holding AG filed Critical Patelhold Patenverwertungs and Elektro-Holding AG
Publication of GB570488A publication Critical patent/GB570488A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04KSECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00Secret communication
    • H04K1/04Secret communication by frequency scrambling, i.e. by transposing or inverting parts of the frequency band or by inverting the whole band

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)

Abstract

570,488. Secret transmission. PATELHOLD PATENTVERWERTUNGS- & ELEKTRO-HOLDING AKT.-GES. March 16, 1943, No. 4286. Convention date, Dec. 20, 1941. [Class 40 (iv)] Secrecy is obtained by attenuating at least a substantial part of the speech band, the attenuation being dependent on frequency and variable with time. The speech band may be divided into sub-bands of equal or different widths, the attenuation over a sub-band being constant or varying with frequency ; some or all of the sub-bands may be displaced in frequency, with or without inversion. The speech frequencies may be equalized initially. In the arrangements shown, original speech Zo is divided by filters into 5 sub-bands which are displaced, by modulation and selection of lower side bands, to a common range 3000-3500 #. The outputs of the modulators M are connected by a permutation switch R to selected attenuators W which may be greater in number than the number of sub-bands, the selection being changed from time to time. The outputs of the attenuators are connected over a further permutation switch Q to devices C providing different delays and connected by a third permutation switch P to modulators N which displace the sub-bands from the common range so that they are distributed over the whole of the speech range. The delay stage may precede the attenuation stage or the delay stage may be omitted. The receiver, which performs corresponding restoring operations, has its permutation switches synchronized with those at the transmitter. The permutations preferably occur at a frequency greater than syllable frequency. The attenuators may comprise valves or other elements controlled by variable voltages which may be differently phased voltages derived from a common source.
GB4286/43A 1941-12-20 1943-03-16 Improvements in systems for the secret electrical transmission of speech Expired GB570488A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH570488X 1941-12-20

Publications (1)

Publication Number Publication Date
GB570488A true GB570488A (en) 1945-07-10

Family

ID=4520880

Family Applications (1)

Application Number Title Priority Date Filing Date
GB4286/43A Expired GB570488A (en) 1941-12-20 1943-03-16 Improvements in systems for the secret electrical transmission of speech

Country Status (3)

Country Link
CH (1) CH228346A (en)
FR (1) FR891738A (en)
GB (1) GB570488A (en)

Also Published As

Publication number Publication date
FR891738A (en) 1944-03-17
CH228346A (en) 1943-08-15

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