| 摘要 |
PROBLEM TO BE SOLVED: To easily confirm the operating state of a video processing circuit from a video signal actually inputted to an input part with the inexpensive diagnostic system of simple structure. SOLUTION: An input part 2 and an output part 3 are connected by a cable 20, an input terminal (b) of a switching circuit 5 is connected to an output terminal and when a reference signal is outputted from a reference signal generator 4 after the reference signal generator 4 is switched to a state not to apply any special effect to a signal, this reference signal is inputted from the output part 3 through the cable 20 to the input part 2. During this operation, when an input terminal (a) of the switching circuit 5 is connected to the output terminal by the switch timing signal of a timing generator 21 and the reference signal generator 4 is switched to a state to apply the special effect to the signal, the special effect is applied to the reference signal inputted to the reference signal generator 4, the data of the reference signal, to which the special effect is applied, are sampled by a sampling circuit 6, afterwards, the value of the data is compared with the reference value of a reference value circuit 8 by a comparator circuit 7 and it is displayed on a display 9 whether a video processing circuit 1 is normal or not.
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