Tracer nocks turn off by passing by a magnet mounted on the riser shelf. They are turned off by passing them back over the magnet...

I don't have any of these -- YET. I'm actually thinking of switching from my A/C/C's JUST so I can shoot these next year; they're the cat's meow, that's for sure... and from what I hear from fellow Pro Staffers... MUCH, MUCH better than Lumenocks.