| 摘要 |
PURPOSE:To prevent charged information from being copied by modulating an oscillation signal of prescribed frequency with an address code supplied to a terminal device and mixing respective parts corresponding to respective bits with a composite video signal corresponding to respective horizontal scanning periods of the composite video signal. CONSTITUTION:An address signal generating circuit 5 and an address signal superposing circuit 6 mix the characteristic codes supplied to the terminal device including a receiver 2 with the video signal and then sends out the composite signal to a video signal amplifying circuit 3. Namely, oscillation signals of one or plural frequencies are generated, for example, amplitude-modulated to generate an address signal indicating and address code characteristic to the terminal, and this address signal is mixed with the composite video signal by superimposing, etc., corresponding to the respective horizontal scanning periods of the composite video signal. Therefore, when illegal copying operation is performed, a terminal device which performs the illegal copying is found easily and speedily. Consequently, the illegal copying operation is precluded. |
