I found most of the interviews fairly relaxed, though I agree that having some knowledge about the company and the equipment makes an impression. I was never really quizzed about JARs (neither FARs), but that might be a picularity of the interviewer.
Indeed, the human resource folks often don't have a (major) clue about the subject anyways, so chances are that they won't be indulging to deeply into specifics.
Good luck!
fcit