The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 10, 1978
Filed:
Feb. 24, 1976
Gretag Aktiengesellschaft, Basel, CH;
Abstract
A method of scrambling and unscrambling speech transmissions by first dividing the speech frequencies into two frequency bands and reversing their order by modulating the speech information, the width of the bands being varied by varying the carrier frequency used in the modulation process, adding to the reversed frequency bands at least one supplementary signal derived from the modulation process and transmitting the resultant signal. The transmitted signal is unscrambled by first subtracting from it a supplementary signal which is generated at the receiving station from the received scrambled signal, the last mentioned supplementary signal being identical to that added to the reversed frequency band signal prior to transmission and then subjecting the resultant signal to the same modulation processes as referred to above to reassemble the frequency bands into a frequency band containing substantially the same speech frequencies as those that are scrambled. Apparatus for carrying out the above method can comprise a separate transmitter and receiver or a single transmitter/receiver whose mode of operation is controlled by a speech key, the transmitter and receiver each including a frequency scrambling device employing modulators and a time scrambling device for generating the supplementary signal.