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4. Up arrow Key
The Up key is used to select a certain option on a menu.
In some menu option, the Up arrow key is mostly used to increase
the value, such as: sensitivity value, noise reject value, depth
alarm value, etc.
5. Down arrow Key
The Down arrow key is used to select a certain option on a menu.
In some menu option, the Down arrow key is mostly used to
decrease the value, such as: sensitivity value, noise reject value,
depth alarm value, etc.
