Furuno 520 Operator's Manual page 49

Locking the control unit
The LOCK feature renders the following commands inoperative from the control unit at
which the LOCK feature has been actuated.
Menu operation
Changing the steering mode
Course setting
Waypoint switching
1. Rotate the course control knob to select "LOCK" from the SYSTEM SETUP menu.
2. Press the course control knob to show the lock options window.
3. Rotate the course control knob to select "LOCK" or "UNLOCK" as appropriate.
4. Press the course control knob.
To unlock, press the [STBD] (►) key while holding the [TURN/MENU] key down.
UNLOCK
LOCK
Lock options window
4. MENU OPERATION
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