Re: That's a Graflex, right (Force Awakens teaser trailer #2)?
Please don't this as coming off rude because I'm loving all these pictures being posted, but coming from a strategic point of view. I don't think with all of today's technology they would be forced to power this saber with a battery pack off screen or worn on a belt. They can power them just like we power them today with little lithiums. I totally see the on/off switch and as going to bring that up but someone else posted before me. So I got to thinking what the heck that big black cap is, and another person suggested maybe a wireless antenna, which I can see as well.
wirelessly triggering the ignition of the blade. One other thing is maybe it is a potentiometer, which can brighten or dull the blade to get that right lighting effect in different sets ( inside or out, day and night)