Capacitive coupling

From HwB

A capacitor is used together with the internal resistor of the input (input impedance) as a high-pass filter. DC component of the signal will be removed.

A 220 µF electrolyte capacitor rated for 6.3V is typical for video signals.

                      +           Video display
Video source ---------||---------O--===---GND
                     220uF          75Ω