GB570488A - Improvements in systems for the secret electrical transmission of speech - Google Patents
Improvements in systems for the secret electrical transmission of speechInfo
- 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
Links
Classifications
-
- 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
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.
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) |
-
1941
- 1941-12-20 CH CH228346D patent/CH228346A/en unknown
-
1942
- 1942-11-18 FR FR891738D patent/FR891738A/en not_active Expired
-
1943
- 1943-03-16 GB GB4286/43A patent/GB570488A/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
FR891738A (en) | 1944-03-17 |
CH228346A (en) | 1943-08-15 |
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