| 摘要 |
PURPOSE:To realize a charged TV broadcast in a simple constitution, by giving a scramble process to the signal level with an AC signal obtained from an AC power source for transmission and then giving a scramble process to the received signal with an AC signal synchronizing with the precedent AC signal. CONSTITUTION:The composite video signal CV1 received a certain pedestal level is supplied to the signal switch circuit 3 along with the signal CV2 which is shifted via the level shift circuit 2, and then turned into the signal having the signals CV1 and CV2 arranged alternately by the rectangular wave SWS which is obtained by giving a waveform shaping to the AC signal ACS of an AC power source. The above-mentioned signal received through the antenna 7 is supplied to the electronic control attenuator 11 and then receives such amount of attenuation by which the peak level in the period of high level of the control signal SWR obtained by giving a waveform shaping to the AC signal ACR synchronizing with the signal ACS of the transmission side becomes in agreement with the peak level in the period of low level. Thus the signal is supplied to the picture receiver 12 in the form of the normal TV signal. |
