| 摘要 |
In a television transmission system comprising an analog video channel scrambled with a control word which is changed occasionally and a NICAM sound channel scrambled with a control word which is also changed occasionally, and different scrambling and modulation circuits having independent clocks for the sound and video signals, a single control word generator is used for the sound and video signals and when this control word is changed for the video signal (17), a bit or a specific group of bits is incorporated in the subsequent sound data packet (18) indicating that a new control word is available, but the new control word will only be used for a subsequent data packet (19).
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