Signal transmission apparatus and signal transmission method

A signal transmitting apparatus for transmitting a digital signal representative of contents of information to be transmitted, comprising:

• a conversion part for converting the digital signal to an analog signal to be one of outputted and transmitted together with the digital signal;
• a protection detecting part for determining whether the contents are protected by copyright;
• and
• a copyright protecting part for performing a copyright protection operation for the analog signal when the contents are determined as protected by copyright based on a result of the determination conducted by the protection detecting part.

A signal receiving apparatus for receiving a digital signal representative of contents of information, comprising:

• an authentication part for determining if the contents are protected by copyright;
• a conversion part for converting a digital signal to an analog composite video signal when the digital signal of the contents is an image signal;
• a signal generating part for generating a copy-guard signal;
• and
• a signal adding part for superimposing the copy-guard signal on the composite video signal when the authentication part determines that the contents are protected by copyright.

A signal transmission system comprising:

• a signal transmitting apparatus for transmitting a digital signal representative of contents of information to be transmitted, comprising:
• a conversion part for converting the digital signal to an analog signal to be one of outputted and transmitted together with the digital signal;
• a protection detecting part for determining whether the contents are protected by copyright;
• and a copyright protecting part for performing a copyright protection operation for the analog signal when the contents are determined as protected by copyright based on a result of the determination conducted by the protection detecting part;
• and
• a signal receiving apparatus for receiving a digital signal representative of contents of information, comprising:
• an authentication part for determining if the contents are protected by copyright;
• a conversion part for converting a digital signal to an analog composite video signal when the digital signal of the contents is an image signal;
• a signal generating part for generating a copy-guard signal;
• and a signal adding part for superimposing the copy-guard signal on the composite video signal when the authentication part determines that the contents are protected by copyright.