04058677 is referenced by 7 patents and cites 5 patents.

Intelligence, such as voice signals, is scrambled for secrecy communication by translating the frequency spectrum of the intelligence by mixing the signals within the frequency spectrum with a local oscillator signal having a frequency that varies between a plurality of discrete frequencies at a selected rate. The translated spectrum is split into two or more channels, and the scrambled intelligence having a frequency spectrum above a selected value is passed through a first channel wherein the frequency spectrum of the signals is reduced to a frequency spectrum at the lower end of the spectrum of the unscrambled intelligence that is not being used by the translated intelligence. The entire frequency spectrum of the translated intelligence is passed through a second channel and the output of each channel is combined and the bandwidth thereof is limited to a selected bandwidth.

In a complete communication system the scrambled intelligence is unscrambled by translating the frequency spectrum of the scrambled intelligence by mixing the signals within the frequency spectrum of the scrambled intelligence with a local oscillator signal having frequencies that vary between a plurality of discrete frequencies at a selected rate in synchronism with the local oscillator signal of the scrambler unit. The translated scrambled input is passed through two or more channels with the signals above a selected frequency level being passed through a first channel wherein the frequency spectrum of the scrambled intelligence is reduced to the frequency spectrum at the lower end of the frequency spectrum of the unscrambled intelligence that is not being used by the translated intelligence and the outputs of the channels are combined as clear intelligence and bandwidth limited.

Title
Sound scrambling equipment
Application Number
464365
Publication Number
4058677
Application Date
July 30, 1975
Publication Date
November 15, 1977
Inventor
William H Draeger
Corona
CA, US
Peter Maitland
Fort Lauderdale
FL, US
Agent
Christie Parker & Hale
Assignee
Lear Siegler
CA, US
IPC
H04K 1/04
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