Grass Valley 1200 Operation Manual - Manual (Page 56)

3-10
Section 3 — Controls & Menus
DSK Preview
When you select [DSK PREVIEW], the preview monitor option
displays the downstream key over the current Program
background, and the Keyer and Key bus delegate to the DSK.
DSK Cut
When you press the [DSK CUT] pushbutton, the downstream key
immediately cuts on air (or off if it was already on).
DSK Mix
When you press the [DSK MIX] button, the downstream key mixes
on over the Program output (or off if it was already on) at the
frame rate shown in the DSK Transition Rate display. If you press
the button a second time during a transition, the key transition
will reverse.