NEC PA721X User Manual page 106

[IMAGE OPTIONS]
CLOCK ................... Use this item to fine tune the computer image or to remove any vertical banding that might appear. This
function adjusts the clock frequencies that eliminate the horizontal banding in the image.
This adjustment may be necessary when you connect your computer for the first time.
PHASE ................... Use this item to adjust the clock phase or to reduce video noise, dot interference or cross talk. (This is
evident when part of your image appears to be shimmering.)
Use [PHASE] only after the [CLOCK] is complete.
5. Using On-Screen Menu