To generate a multiple video signal generated by video recorder 2, a conforming or nonconforming ID signal superimposed on a video signal is detected by an ID detecting circuit 11. Operation of appending a conforming ID signal is switched by a selector 14 based on the output of a state determination...http://www.google.com/patents/US6744475?utm_source=gb-gplus-sharePatent US6744475 - Video switching apparatus for switching between a plurality of channels
