To perform display with high visibility and excellent image quality when outputting a plurality of video signals onto a monitor of a master unit in the same timing by matching vertical synchronism of video signals imaged by cameras of a plurality of slave units, respectively.

The vertical synchronism of video signals imaged by cameras 101 of a plurality of slave units 1a, 1b, ..., 1n is matched by a reference synchronizing signal generated by a signal processing section 203 of a master unit 2. Furthermore, the vertical synchronism of video signals imaged by the cameras of the plurality of slave units each including a synchronous coupling function 104 is matched by external synchronization control signals generated by external signal sources 3a, 3b, ..., 3n or by the reference synchronizing signal generated by the signal processing section of the master unit.

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