A free wheel hub control system for a free wheel hub mechanism is positioned between a drive shaft and an axle hub supported by a spindle. A flexible printed circuit is disposed between an inner face of the spindle and an outer face of the drive shaft to transmit a control signal to an electric element...http://www.google.com.au/patents/US5018597?utm_source=gb-gplus-sharePatent US5018597 - Free wheel hub control system
