Lenovo LXM-WL19CH - Manual (Page 13)

CLOCK (pixel frequency) controls the number of pixels scanned by one
horizontal sweep. If the frequency is not correct, the screen shows vertical
stripes and the picture has not correct width.
FOCUS adjust the phase of the pixel clock signal. With a wrong phase
adjustment the picture has horizontal disturbances in light picture.
For FOCUS and CLOCK adjustment use Win 95/98/2000/ME shutdown mode
pattern.
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