Hitachi 50EX8K/10B - Manual (Page 19)

REAR PANEL CONNECTIONS
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• A single VCR can be used for VCR#1 and VCR#2, but note that a VCR
cannot record its own video or line output (input 1 in the example on pg.
12). Refer to your VCR operating guide for more information on "line"
input-output connections.