does a football coach talk on the headset DURING a play?
I don't know why this never occurred to me before. so quarterbacks have headsets in their helmets so they can communicate with the coaching staff. I was always under the impression that they only used it before the play, just to prevent using a runner, but is the coach ever on the microphone during the play? maybe telling the quarterback where somebody is open if he can't see it
The headsets are active between plays, and have one way communication with one player on each side. Typically this is the quarterback on offense and a team captain/play caller on defense. These players wear special helmets typically marked with a green dot on the back.
The refs or other officials cut off communication when the play clock reaches 15 seconds, preventing the kind of real-time communication you suggest.
It does get disabled to the Quarterback, however I believe the Head Coach can flip between channels to talk to Offensive and/or Defensive coordinators during the play.