Question on Arc 4+ electronic switch

[Anglepoise]

How did the power get from the battery positive at the bulb end of the flashlight to the electronic switch in the tail cap.
I do not own an Arc but am interested in building an electronic switch and any info would be appreciated. We need a good tail cap switch that can have on ,off, momentary and ramp dimming.

 

[PeLu]

There is no electronic switch on the tail end. Everything electrical is in the head.

 

[Anglepoise]

Thank you.