Toyota Repair: 2000 LC VSC & Center Differential Lights, vehicle stability control, differential lock

Question
2000 Land Cruiser---Two warnings lit up on the dashboard this evening:  VSC OFF and the diagram for the Center Differential Lock indicator.  After cross-referencing the owner's manual, I finally figured out that I had accidentally hit the center differential lock button on the dash.  All is now well but I want to know when one would want to turn off the vehicle skid control & center differential.  Would this be used while driving over deep sand (with the tires properly deflated)?  Thanks!

Answer
The center diff should not be locked unless there are extreme driving conditions such as mud,sand snow/ice, when the diff is locked the vehicle stability control(VSC) is disabled turning the light on the dash on. Locking the center differential applies equal power to all the wheels.