Telegraphy – Systems – Line-clearing and circuit maintenance
Patent
1975-01-29
1976-11-09
Birmiel, H.A.
Telegraphy
Systems
Line-clearing and circuit maintenance
325 32, 325 58, 179 15R, 178 22, H04L 900
Patent
active
039912710
ABSTRACT:
The specification discloses a voice scrambler technique wherein a voice signal is split into a plurality of discrete frequency sub-bands. A random code genertor generates a randomized sequence of digital signals. A preselected first portion of each of the digital signals is utiized to control the rearrangement of the order of the frequency sub-bands according to a limited subset of all possible combinations of rearrangements of the frequency sub-bands. The limited subset is chosen to include only the most unintelligible of the possible combinations of rearrangements of the frequency sub-bands. A preselected second portion of each of the digital signals is utilized to control the random inversion of ones of the frequency sub-bands. The rearranged and inverted frequency sub-bands are then transmitted over a conventional voice communication line to a similar voice scrambler unit which operates in synchronism to rearrange and invert the frequency sub-bands to the original state in order to render the voice signal intelligible. The system includes a unique synchronism technique which automatically compensates for time delays in transmission and which allows tolerance of transmission errors, with the randomized signal generator being rapidly stepped prior to initial transmission to generate a prime word, the rapid advancement serving to compensate for transmission path delay.
REFERENCES:
patent: 2411683 (1946-11-01), Guanella
patent: 3463911 (1969-08-01), Duproz et al.
patent: 3586776 (1971-06-01), Salava
patent: 3773977 (1973-11-01), Guanella
Branscome Kenneth M.
Feath William M.
Goode George E.
Heizer Kenneth W.
Morgan Barrie O.
Birmiel H.A.
Datotek, Inc.
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