volts and light can be used interchangeably
Reminds me of DS Audio's optical cartridges!
In these, an electrically powered light-emitting diode (LED) illuminates a screen attached above the stylus. The screen normally stops the light from reaching a photo-sensitive receptor. When the stylus moves, the screen unblocks some of the receptor and some of the photons interact with electrons to create a voltage signal. Oversimplified description, I know.
Another LED sits at the front of the cartridge to show the power is on (and the afficionados how much you spent).
Einstein would be ecstatic!

