faults or brightness set very high; in this case a white retrace line shows on the screen, often alternating between fairly steep diagonals from right to left and less-steep diagonals back from left to right, starting in the lower right of the display.

In analog television systems the vertical blanking interval can be used for datacasting (to carry digital data), since nothing sent during the VBI is displayed on the screen; various test signals, VITC timecode,