Take a look at this link. http://www.koga-signature.com/docs/L...ux_English.pdf. It might be useful. It reads like the Power line of the tail light connects to the power switch on the eDelux, and the ground wire connects to the frame. This makes sense if the hub dynamo was also grounded to the frame. I'm not familiar with this setup, but that's how vehicle lights are wired on older cars. The negative side of the alternator and battery are grounded to the vehicle frame. A single power/positive wire to the light was all that was needed because the light was grounded to the frame.