| 摘要 |
PURPOSE:To attain the security and the degradation of quality of a voice signal by applying AM modulation to a transmission voice signal by a pulse corresponding to the tail ridge of the scrambled horizontal synchronizing signal, mixing the video signal subjected to scramble processing and converting it into an RF frequency at the encoder side. CONSTITUTION:A signal part of the transmission voice signal corresponding to the tail ridge of the scrambled horizontal synchronizing signal is AM- modulated. Since the part is always delayed to the scrambled horizontal synchronizing signal, a person trying furtive audience can not recognize the scrambled horizontal synchronizing signal period except for the elapse of the period at all times. Moreover, since the voice signal corresponding to the tail ridge of the scrambled horizontal synchronizing signal is AM-modulated, then the width of the AM modulation part of the scrambled voice signal is decreased and the effect of the voice is reduced in comparison with a conventional device where the AM modulation part appears at the entire horizontal synchronizing signal period. |
