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2 answers

The device usually uses the friction of the tire. I think they came out with one that uses magnets, though.

2007-03-28 07:46:54 · answer #1 · answered by Brundige 4 · 0 0

Through a dynamo.

2007-03-28 14:42:06 · answer #2 · answered by Anonymous · 0 0

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