Originally Posted by VonHelm
It's essentially just a big switching transistor.
About the electronics ... one of the photos of the controler shown in the attached link revealed one of the components was an electrolytic capacitor. Seeing this was dissapointing. Electrolytic capacitors have lousy thermal properties and inferior resistance to vibration, but are otherwise favoured by $/capacitance (i.e. cheap). In view of BMW's reputation for reliability I'd expected to see a more robust type of capacitor used on my "unstoppable" bike.
Shortcut to: http://www.motorcycleinfo.co.uk/index.cfm?fa=contentGeneric.nvxszdkebklxuaer&pageId=428065