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 generator generates a randomized sequence of digital signals. A preselected first portion of each of the digital signals is utilized 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. The system includes an alarm function which becomes operative upon the occurrence of a malfunction and also includes various other safety devices to prevent the transmission of uncoded voice data in case of a malfunction of the system.
Inventors
👤 Kenneth M Branscome
👤 William M Feath
👤 George E Goode
👤 Kenneth W Heizer
👤 Barrie O Morgan
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-30 03:06
CPC Classifications
H; H04; H04K; H04K1/00; H04K1/04
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
108 words
A method of determining optimum subsets of a plurality of possible arrangement permutations of frequency sub-bands of a voice signal for use in a voice scrambler system comprising: grouping said possible arrangement permutations into a plurality of possible subsets while excluding preselected forbidden arrangement permutations which provide intelligible voice data; cross-correlating the arrangement permutations of each possible subset; assigning an articulation index representative of the intelligibility to each arrangement permutation of the possible subsets having the lowest cross-correlation indexes; and determining the subset having the lowest average articulation index as the optimum subset for use in rearranging the order of the frequency sub-bands in a voice scrambler system.
Claim 2
Independent Claim
108 words
A method of determining optimum subsets of a plurality of possible arrangement permutations of frequency sub-bands of a voice signal for use in a voice scrambler system comprising: grouping said possible arrangement permutations into a plurality of possible subsets while excluding preselected forbidden arrangement permutations which provide intelligible voice data; cross-correlating the arrangement permutations of each possible subset; assigning an articulation index representative of the intelligibility to each arrangement permutation of the possible subsets having the lowest cross-correlation indexes; and determining the subset having the lowest average articulation index as the optimum subset for use in rearranging the order of the frequency sub-bands in a voice scrambler system.
Claim 3
Dependent Claim
18 words
The method of claim 1 wherein an optimum subset of sixteen permutations of five frequency sub-bands is determined.
Claim 4
Dependent Claim
20 words
The method of claim 2 wherein ones of said sixteen permutations are randomly selected by random four bit digital words.