Ever since I got my Rover last year I've been wondering what the heck is this switch? It doesn't appear to do anything that I can tell, at least it's not a self destruct switch.
Just recently returned from a trip to Germany last week, which incidentally I saw a lot of Rovers: Discos, Defenders and Range Rovers, oh my. When we got on the Autobahn I saw the symbol for the A/B which curiously looks like my the symbol on my switch.
Is it a dimming feature? I'm not wired for fog lamps I know that.

 

Cruise Control.

 

No wonder I couldn't figure it out because the C/C is disconnected at the moment. Thanks.

 

If you would like an electronic copy of the owner's manaual it is part of the RAVE download, which has workshop, electrical, owners, etc. Free links below.