> As another idea - what about the magnetic transformer used at the
> base of the heads on a VCR.? More or less a double pot core with
> the primary rotating and the secondary fixed.  Tuning the windings
> to resonance will improve the efficiency

That's an idea. Roman, you're Mr WhatgoesoninsideVCRs, any
comment ?

> Or a solar cell with a focussed lamp providing the illumination?

I used to have a source for the miniature 0.5V calculator cells but
they disappeared. Maybe I'll start looking around again

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