Originally Posted by Darth Moeller
Thats what he just said, its not on his arm, its like a choker-style necklace around his neck.
Wonder why he'd need a slave collar when one of Vader's signature uses of the force is to choke people over considerable distances. Sounds a bit weird to rely on technology for something he could do anyway.
I guess it's a plot device to allow you to break free from enslavement, it's easier to destroy an object than the force.