| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem of edge production even when a super key input signal is superimposed by itself. SOLUTION: A-gate circuits 1-1 to 1-n gate super video input signals when the super video input signals v1 to vn are superimposed by a super key. B-gate circuits 3-1 to 3-n gate the super video input signals when the super video input signals v1 to vn are superimposed by themselves. C-gate circuits 5-1 to 5-n gate the super video input signals when the super video input signals v1 to vn are superimposed by themselves. An edge key generating circuit 7 generates an edge key signal ek from the super key input signals passing through the A-gate circuits. The super key input signals passing through the B-gate circuits are switched by a changeover circuit 4 according to a switching signal sw from the C-gate circuits and become a super video signal v0.
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