| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent a noise video image from being outputted onto a monitor, by rightly switching a changeover switch even in the case where an AGC circuit operates at a maximum. SOLUTION: In a system, a video camera is installed on a platform of a station, a train and the platform are shot by the video camera, frequency-modulated and optically transmitted to an optical receiver on the train by an optical transmitter, and an output signal of the optical receiver is demodulated by a video signal demodulation apparatus 12 and displayed on a monitor in a driver's room. In such a system, a first changeover switch 27 and a second changeover switch 37 are provided within the video signal demodulation apparatus 12, a squelch level determination circuit 33 for controlling switching of the changeover switches 27, 37 in accordance with a reception signal level is provided and a squelch function is duplexed, thereby preventing a malfunction caused by noise. COPYRIGHT: (C)2007,JPO&INPIT
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