Marine PC MPC-SL21W User Manual page 27

"KEY LOCK" Mode Function setting screen:
When you press "MENU" and "BRIGHTNESS" KEY simultaneously for 3 seconds, you will
enter the "KEY LOCK" mode. At the same time, the screen will show "KEY LOCK" image
as below for 5 seconds and then disappear.
In the "KEY LOCK" mode, it will be no function to press any key. When you press the key
in the "KEY LOCK" mode, the screen will show "KEY LOCK" image as below for 5 seconds
and then disappear.
To Release/Unlock "KEY LOCK" Mode Function setting screen:
In the "KEY LOCK" mode, when you press "MENU" and "BRIGHTNESS" KEY simultaneously
for 3 seconds, you will release/unlock the "KEY LOCK" mode. At the same time, your
screen will show "KEY UNLOCK" image as below.
Page 27