| 摘要 |
PURPOSE:To enable the exact transmission of a video signal even if the fluctuation in light conversion efficiency or the fluctuation in intrinsic characteristic arises in isolation devices. CONSTITUTION:A variable gain amplifier 14 is provided on the patient circuit side of the device in which the patient circuit is connected via the isolation devices 12a, 12b to the output circuit. A sample-hold circuit 18 which sample- holds the reference level of the video signal is provided on the output circuit side thereof. A control loop to feed the sample-held signal back to the variable gain amplifier 14 in the state of including the isolation devices 12a, 12b and controlling the level of the video signal so as to maintain the specified level is formed. Then, this loop acts to compensate the fluctuation component even if the fluctuation arises in the video signal. The stable transmission of the video signal is thus enabled.
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