IBM 9513AG1 - T 55A - 15" LCD Monitor User Manual page 21

OSD Lock / Unlock
This feature allows you to secure the current control settings, while allowing
the user to adjust Brightness and Contrast, so that they cannot be
inadvertently changed. You can unlock the OSD controls at any time by using
the same procedure.
Push and hold the button for 10 seconds to Lock or to Unlock. When locked, a
"LOCKED" message will be displayed.
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