US PATENT SUBCLASS 380 / 38
.~ Frequency shift or inversion
Current as of:
June, 1999
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380 /
HD
CRYPTOGRAPHY
9
DF
ELECTRIC SIGNAL MODIFICATION (E.G., SCRAMBLING)
{18}
38
.~ Frequency shift or inversion {1}
39
DF
.~.~
> With plural band pass filters
DEFINITION
Classification: 380/38
Frequency shift or inversion:
(under subclass 9) Subject matter which modifies a segment of the frequency spectrum of the information signal.
SEE OR SEARCH CLASS
370, Multiplex Communications,
343+, and 480+ for combining or distributing information via frequency channels, absent cryptography.
375, Pulse or Digital Communications,
240+, for bandwidth compression or expansion to facilitate digital signal handling, rather than conceal information.
704, Data Processing: Speech Signal Processing, Linguistics, Language Translation, and Audio Compression/Decompression,
500+, for audio signal bandwidth compression or expansion for purposes other than concealment of information.
