| 摘要 |
Apparatus is disclosed in a video signal processing system for automatically controlling the blanking (black) current level of an image reproducing kinescope having cathode and grid intensity control electrodes. During measuring intervals when cathode blanking current is to be monitored, a fixed voltage is applied to the cathode over the entire measuring interval, and a locally generated auxiliary signal is applied to the grid electrode during a portion of the measuring interval. A version of the grid signal appears as a cathode output signal proportional to the level of cathode blanking current conduction. A voltage responsive sensing network coupled to the cathode provides an output difference voltage proportional to the difference in cathode current conducted over the measuring interval. This voltage is utilized to modify the cathode bias in a direction to produce the desired cathode blanking current level at or in the vicinity of kinescope cut-off. |
