| 摘要 |
Transmitting and receiving circuits of a video signal for power line communication are provided to modulate a video signal, photographed by a camera and amplified, into the video signal of a composition modulation waveform by an oscillation IC, transmit the modulated video signal through a power line via a transformer, demodulate the video signal received through the power line, amplify the demodulated video signal, and transmit the amplified video signal to a monitor, thereby displaying a clear image without configuring a private line or a separate modem. An input control unit(1) of a VR1(Variable Resistor1) controls the input level of a video signal photographed and transmitted from a camera. A bias current control unit(2) converts the video signal of the controlled input level into a bias voltage necessary for signal processing by a VR2, a R1(Resistor1), and a R2. A differential amplifying unit(3) amplifies the video signal through the R1 and the R2 operated by the bias voltage. A modulation unit(4) of a modulation IC(Integrated Circuit) is operated by using the video signal amplified in a broadband by the differential amplifying unit as input power and loads the video signal to a carrier frequency of an oscillation frequency. Transformer units(5) abandons a video signal of an AC(Alternating Current) from the video signal, modulated by the modulation unit, by a transformer(T1) and condensers(C1,C2), performs the voltage-resistance processing of the modulated video signal, and outputs the processed video signal to a power line.
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