Ah, okay. Good Q. If it fails, it doesn't have power. Old-School hotwire; bypass everything would be my *guess.* Cut the bypass when you hit the road again.
Default is open; switches provide power to activate the electromagnets. Switch on and they stay that way until switched off, when they deactivate. (They might disengage for a moment if you back up.) Some folks use toggle switches etc. to prevent accidental switching by human or dog.
As to ARBs...
My experience is (thus far) wildly uneven; things I've done, I've done. Other things I've researched to death, been in rigs that already have them (or competing products), etc. Still other things I'm fairly clueless about; should be doing my first new suspension shortly, so asking questions on...
Harrop/Eaton are the best lockers available. They also open up your prospects when buying a Cruiser, because you're not limited to the--what is it, 7% of 80s that came locked from the factory...