Question

In professional football some players have microphones in their helmets that allow them to communicate on the sideline. What does this indicate?

Answer 1

It can indicate that the player is receiving different plays or updates on plays

Answer 2

NFL rules, says this is a sticker that marks the helmet that is linked up with a two-way microphone radio set, so the coaching staff can communicate with an on-field player. The quarterback on offense and the defensive captain or play-caller are linked up with communicators in their helmets.