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| SECTION H– ELECTRICITY |
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| H 04 | ELECTRIC COMMUNICATION TECHNIQUE |
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| H 04 K | SECRET COMMUNICATION; JAMMING OF COMMUNICATION |
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| Note |
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| In this subclass, the following expression is used with the meaning indicated: |
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| – | "secret communication" includes secret line and radiation transmission systems, i.e. those in which apparatus at the transmitting station modifies the signal in such a way that the information cannot be intelligibly received without corresponding modifying apparatus at the receiving station. |
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1/ | 00 | Secret communication (ciphering or deciphering apparatus per se G 09 C; systems with reduced bandwidth or suppressed carrier H 04 B 1/66; spread spectrum techniques in general H 04 B 1/69; by using a sub-carrier H 04 B 14/08; by multiplexing H 04 J; transmission systems for secret digital information H 04 L 9/00; secret or subscription television systems H 04 N 7/16) |
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1/ | 02 | . | by adding a second signal to make the desired signal unintelligible |
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1/ | 04 | . | by frequency scrambling, i.e. by transposing or inverting parts of the frequency band or by inverting the whole band |
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1/ | 06 | . | by transmitting the information or elements thereof at unnatural speeds or in jumbled order or backwards |
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1/ | 08 | . | by varying the polarisation of transmitted waves |
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1/ | 10 | . | by using two signals transmitted simultaneously or successively |
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3/ | 00 | Jamming of communication; Counter-measures (counter-measures used in radar or analogous systems G 01 S 7/00) |
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