| 摘要 |
A CCTV(Closed Cable TeleVision) system is provided to supply power to a CCTV in a video/audio receiving unit and modulate and transmits a video signal of the CCTV and an audio signal of a microphone to the video/audio receiving unit. A CCTV system comprises a video/audio transmitting unit(200) and a video/audio receiving unit(300). The video/audio transmitting unit comprises a DC/DC converter circuit, a CCTV camera module, a microphone, a voice amplifying circuit, a modulation circuit and a modulation signal amplifying circuit. The DC/DC converting circuit converts DC power supplied from the video/audio receiving unit into power suitable for the video/audio transmitting unit. The DC/DC converting circuit supplies the converted power. The modulation circuit modulates a video signal outputted from the camera module by an AM type and an electrical voice signal outputted from the voice amplifying circuit by an FM type. The video/audio receiving unit comprises a power circuit, a DC power supply circuit, a demodulation circuit, a video amplifying circuit, a voice amplifying circuit, a monitor, a speaker, a video/voice storage unit and a micom circuit. The power circuit supplies DC power to the video/audio receiving unit and the video/audio transmitting unit. The demodulation circuit demodulates video and voice signals from the modulated signal transmitted from the video/audio transmitting unit and outputs the demodulated video and voice signals.
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