Planar PL1920M User Manual page 12

Option 2: OSD & Power button lock – all 5 buttons including the "POWER" button are locked.
Press and hold the ▲ button and then the
button for 3 seconds to lock all 5 buttons.
The TFT LCD Monitor will show an "Lock Out" message for 5~10 seconds and the message will
disappear automatically.
Repeat this step to unlock.
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