Since '94, teams have had analog radio communication from a single coach's headset into the ears of a single player on offense and a single player on defense (signified by those lime-green dots on the back of a helmet) via small speakers in each earhole. But teams complained about the 1- to 2-second delay and the spotty reception; there are incidents of a Madonna rehearsal from a nearby arena piped into a quarterback's helmet during a game in Oakland, Calif., or a San Francisco player hearing Southwest Airlines pilots' chitchat.
The NFL eradicated most of those issues this season by introducing Nebraska-based Gubser & Schnakenberg's digital system. The league claims it now uses more than 260 million different encryption codes to protect teams' frequencies. Still, coaches need to talk quickly during the 40-second play clock, as the transmission shuts off after just 25 seconds.