Zero reference pulse

If the modulation index yields more than % 10 for maximum level input (high residual carrier), the efficiency of the transmission drops, i.e., low contrast.

On the other hand, if the RF level is below % 10 (low residual carrier), aural and visual signals begin to interfere each other.

The receiver has a facility to switch off RF for a short interval in each consecutive line.

The interruption on all lines in a frame is observed as a vertical white bar on a visual monitor.

Taking the level difference between the sync tip and the 0 pulse as % 100, the maximum CVS should be 10% or 12.5%.