What is the OVR/SVC switch?

I have tried the unplugging for about fifteen minutes, and have the unit unplugged now. Will try again this afternoon.

Thanks
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Zone 1: Outlaw 990, Outlaw 7700, Panasonic Plasma, Apple TV, 24" Intel iMac, ReVox A77, Mission 77 Series, Mirage LF-150
Zone 2: McIntosh MA1650, Dual 1219, Smaller Advent Speakers
Zone 3: Victor V, Victor Exhibition Soundbox