NFL Headphones: Who Receives Sideline Communication?

Question
I know that NFL quarterbacks get headphones in their helmets.  Does anyone in the defense and special teams get headphones in their helmets too?  (Btw, I think there was something wrong with the other thread of questions I asked you.  Your last answer didn't show up.  If it's not too much trouble, can you see what's wrong?)

Answer
No.  At this time, the only player who gets a feed from the sideline is the QB.  If you watch the sidelines carefully when the "D" is on the field, the defensive coordinator is usually making all kinds of crazy hand signals, feeding the calls or giving a heads up to whoever is calling the formation on the field (almost always a middle/inside linebacker).