| 摘要 |
PURPOSE:To switch a video signal without deteriorating performance and losing a synchronizing signal with inexpensive circuit constitution by providing a data selection means switching a video switching a command signal, the synchronizing signal and the video signal and a gate circuit. CONSTITUTION:A write of a ramp signal digital data in a memory 3 or a ramp signal memory in the memory 3 is selected during a video signal switching period. A video switching command signal 5 is zero during the period. A selector 4 is in the selecting state while an identification signal 6 is zero, that is, during a video period other than the period including a horizontal synchronizing signal. The selector 4 is in the nonselecting state during the period including the horizontal synchronizing signal, that is, while the identification signal 6 is logical 1 and no horizontal synchronizing signal is not lost. Moreover, a luminance signal during the period is kept to a pedestal level. Then in case of switching a video signal by a panel switch or external control or the like, since the synchronizing signal is not lost, a consecutive composite video signal is obtained. |
