| 摘要 |
<p>An arrangement for tracking the black level reference of a received video signal waveform comprises a capacitive storage means on which a voltage representing the reference may be established, a comparator to one input of which the signal waveform is applied and to the other input of which the voltage representing the reference is applied, and two current sources to charge and discharge the capacitive storage means respectively in dependence on the output of the comparator, the current sources providing currents of values in a ratio dependent upon the distribution of the received waveform above and below the black level reference. <IMAGE></p> |
