Located next to the buttons is a fader bar. On the Mix A bus punch up the video source. Make sure the fader bar is in the correct position. Gradually, move the fader bar from one bank to the other. Preview Bus Sometimes when setting up an effect it is necessary to preview it on the monitor because of its complexity.
Most switcher setups have a preview monitor devoted for such a purpose.
The mix bank is punched up on the preview monitor and the effect can be tested. Some switcher setups will employ a preset system, instead of preview. If Camera 1 was on the program output and the director wishes to go to Camera 3, the technical director will immediately punch up Cam 3 on the preset bank. What used to be a very fancy effect, early in TV, has become very standard on virtually all broadcasts. For example, let's say you wanted to create a composite image with a camera shot in the middle of an electronic still of a picture frame.