Introduced in 1983 and the weird thing is, there's no need for changing battery and they still work (as non-fixie mentioned in this thread).




The sensor-ring mounted in the frontwheel determines the speed and charges a fixed battery system.
First time I saw this was at the Tweewieler RAI of 1984 in Amsterdam. In kinda aquarium with shower heads to show this equipment was waterproof.
A great invention those days and it still fits in nowadays evironment problems.