Just as the change from analog to digital has caused significant changes to the video signal, it has also caused similar changes to the way that we measure the video signal. Scopes have changed from oscilloscopes to computer generated graphic displays of the video signals. Some of these instruments take the same stand-alone form as their predecessors. Others, called rasterizers, separate the electronics and display. The advantage of the second format is that a much larger display can be set to show several different displays simultaneously (Figure 9.1).