| 摘要 |
PURPOSE:To render a person who does not pay a charge to know some part of broadcast contents by performing selectively an action of a cipher machine, by ciphering either a video or a sound and by the person, who does not pay a charge, outputting information of non-ciphered part. CONSTITUTION:In case of ciphering only a video signal, a transmission side 31 ciphers a video signal 20 with aid of the prescribed cipher key 23 by means of a cipher device 22, while non-ciphered sound signal 21 is multiplexed and transmitted by a multiplex circuit 24. A receiving side 32 separates a video and a sound by a separator circuit 30. The sound signal is properly outputted by an output part 27, while the video signal can be decoded by only the audience who will pay a receiving fee and has a decoding key 29. This decoding is carried out by a decoder 28 with aid of the key 29, and its output is properly performed to a monitor 26. However, the person having no such a key can catch more detailed contents than a program guide on newspapers, etc., by means of the free sound signal. |
