Acesonic PK-6000 - Manual (Page 12)

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Unlocking the Screen
In Figures 01 and 02, note the lock icon at the upper right of the screens (unlocked
in 01, locked in 02). Click and hold for 2 to 3 seconds to toggle between the settings.
In Karaoke and Video modes, automatic locking is disabled (you can do it manually).
Otherwise, you set the locking function to your preference by setting the screensaver time.
Figure 01 Figure 02