| 1/00 | Secret communication (ciphering or deciphering apparatus per se
G09C
; systems with reduced bandwidth or suppressed carrier H04B 1/66
; spread spectrum techniques H04B 1/69
; by using a sub-carrier H04B 14/08
; by multiplexing H04J
; transmission systems for secret digital information H04L 9/00
; secret or subscription television systems H04N 7/16, H04N 21/00
) |
| 1/02 | Secret communication (ciphering or deciphering apparatus per se
G09C
; systems with reduced bandwidth or suppressed carrier H04B 1/66
; spread spectrum techniques H04B 1/69
; by using a sub-carrier H04B 14/08
; by multiplexing H04J
; transmission systems for secret digital information H04L 9/00
; secret or subscription television systems H04N 7/16, H04N 21/00
) by adding a second signal to make the desired signal unintelligible |
| 1/04 | Secret communication (ciphering or deciphering apparatus per se
G09C
; systems with reduced bandwidth or suppressed carrier H04B 1/66
; spread spectrum techniques H04B 1/69
; by using a sub-carrier H04B 14/08
; by multiplexing H04J
; transmission systems for secret digital information H04L 9/00
; secret or subscription television systems H04N 7/16, H04N 21/00
) by frequency scrambling, i.e. by transposing or inverting parts of the frequency band or by inverting the whole band |
| 1/06 | Secret communication (ciphering or deciphering apparatus per se
G09C
; systems with reduced bandwidth or suppressed carrier H04B 1/66
; spread spectrum techniques H04B 1/69
; by using a sub-carrier H04B 14/08
; by multiplexing H04J
; transmission systems for secret digital information H04L 9/00
; secret or subscription television systems H04N 7/16, H04N 21/00
) by transmitting the information or elements thereof at unnatural speeds or in jumbled order or backwards |
| 1/08 | Secret communication (ciphering or deciphering apparatus per se
G09C
; systems with reduced bandwidth or suppressed carrier H04B 1/66
; spread spectrum techniques H04B 1/69
; by using a sub-carrier H04B 14/08
; by multiplexing H04J
; transmission systems for secret digital information H04L 9/00
; secret or subscription television systems H04N 7/16, H04N 21/00
) by varying the polarisation of transmitted waves |
| 1/10 | Secret communication (ciphering or deciphering apparatus per se
G09C
; systems with reduced bandwidth or suppressed carrier H04B 1/66
; spread spectrum techniques H04B 1/69
; by using a sub-carrier H04B 14/08
; by multiplexing H04J
; transmission systems for secret digital information H04L 9/00
; secret or subscription television systems H04N 7/16, H04N 21/00
) by using two signals transmitted simultaneously or successively |
| 3/00 | Jamming of communication; Counter-measures (counter-measures used in radar or analogous systems G01S 7/00) |