Square DŽ Arc-fault Circuit Interrupters (AFCI)
The Truth About AFCIs I should point out these do not serve the same purpose as GFCIs, which are intended to keep you from doing the 60HZ shuffle. AFCIs are designed to detect arcing and open the circuit before a fire can start.
An inline fuse inside the ballast enclosure. The little black item with the red wire going into it is an in-line fuse housing. It would open the hot 120V circuit lead if the ballast starts pulling more current than it should. You can get the housing and fuse from radio shack. BTW, the tape you see is not on twisted wire, its over an insulated wire nut. I add the tape in boxes that vibrate, like magnetic ballasts or cieling fans.
Switch and Fuse. One has the fuse cover closed, one open. You can get these at Lowes. They mount in a standard handy box, and come prewired. I've also installed these right on the ballast enclosure. The fuse just screws out for replacement.