| 摘要 |
<p>Various methods and systems are disclosed for television transmission, as well as for scrambling a plurality of input signals for secure transmission thereof. The scrambling technique, in one form, includes modulating an in-phase component of at least one carrier signal in response to one and then another of a plurality of input signals in a sequence of time intervals such that parts but not all of the one and another of the input signals are carried by the in-phase component. A quadrature component of the carrier signal is similarly modulated in response to the aforementioned one and another of the plurality of input signals in a sequence of time intervals such that the in-phase and quadrature components together are carriers of the one and another of the input signals in their entirety. The modulated in- phase and quadrature components are combined for transmission. A decoder for unscrambling and selecting one of the plurality of signals is also disclosed. The various television transmission methods and systems involve the provision of additional audio signals, in scrambled or unscrambled form, with the normal television audio and video signals so that a multilingual programme service as well as other services can be provided.</p> |
