| 摘要 |
PURPOSE:To make the phase detecting sensitivity different between a vertical synchronizing pulse period and other pulse periods by using a pseudo composite synchronizing signal where the polarity of a vertical synchronizing pulse is inverted as a reference input. CONSTITUTION:A composite synchronizing signal inputted to an input terminal 1 is applied to a vertical pulse extracting means 2 and a vertical pulse having the same period as that of a vertical synchronizing pulse is led out of an output terminal 3. Then this vertical pulse is applied to one input of an EX-OR circuit 4 and ORed exclusively with the composite synchronizing signal applied to the other input. As a result, the pseudo composite synchronizing signal inverted only during the vertical synchronizing period is obtained at an output of the EX-OR circuit 4 and this is given to a gain adjusting means 12 via an inverter 5. On the other hand, a vertical pulse from the output terminal 3 is also applied to the gain adjusting means 12, thereby allowing to make the phase detecting sensitivity different between the vertical synchronism period and other periods. |
