Originally Posted by
Michel Gagnon
– Both Shimano hubs are grounded to the frame. Therefore, if you use a Lumotec Oval Plus, it has to be mounted on a plastic bracket to insulate it.
I used to think this too, and when I installed my first Oval Plus it was on all of the time. Then somebody pointed out that there's a Phillips screw on the Oval Plus which, if you loosen or remove it, disables the ground connection so the switch works normally.
Sheldon "Who Knew?" Brown