04052565 is referenced by 87 patents and cites 4 patents.

A digital speech scrambler system allowing for the transmission of scrambled speech over a narrow bandwidth by sequency limiting the analog speech in a low-pass sequency filter and thereafter multiplying the sequency limited speech with periodically cycling sets of Walsh functions at the transmitter. At the receiver, the Walsh scrambled speech is unscrambled by multiplying it with the same Walsh functions previously used to scramble the speech. The unscrambling Walsh functions are synchronized to the received scrambled signal so that, at the receiver multiplier, the unscrambling Walsh signal is the same as and in phase with the Walsh function which multiplied the speech signal at the transmitter multiplier. Synchronization may be accomplished by time division multiplexing sync signals with the Walsh scrambled speech. The addition of the sync signals in this manner further masks the transmitted speech and thus helps to prevent unauthorized deciphering of the transmitted speech.

Title
Walsh function signal scrambler
Application Number
5/581695
Publication Number
4052565
Application Date
May 28, 1975
Publication Date
October 4, 1977
Inventor
Charles Michael Reeves
Dalton
MA, US
Denmer Dix Baxter
Orlando
FL, US
Agent
Howard L Bernstein
Gay Chin
Julian C Renfro
Assignee
Martin Marietta Corporation
FL, US
IPC
H04K 1/00
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