in addition to the line tech one from Bush and Muller [riv bike likely gets them through Peter white cycles, the importer]
mine is dynamo powered, RBW link shows the battery version..

I have had their 4D Toplight on 2 versions, battery(2AA) and dynamo power + battery.
there are 4 diodes lighting up the whole broad lens , so as to be seen well from the sides ,
as well as the back..
the German made light, option .. 'Senso' in the battery power ,
detects motion and will turn on, and after stopping a while, turn off on its own.

newer hub dynamo lights add a capacitor in the circuit,
and will also stay on a minute or so after stopping.


when I had just a passive reflector bracket.. Cat eye tL 500 an oval , fit in its place..

the electronic gadget thread also has past discussion of lights..
some people use a bunch of them all at once ..

maybe 1 battery will last longer than the next one, in light 2 and 3..
do have to buy more batteries..