NFL television side line shots often include a bank of black wall telephones behind the player’s bench. They appear to be on a trailer of some sort. I have never seen them in use, what is their purpose?
They use them to talk to the team folks in the booth upstairs, often the assistant OC or DC. Cell phones are banned on sidelines, I believe.
The NFL introduced tablets to the sidelines this season (Microsoft Surface), but their use is strictly controlled. They can be only be used to look at still photos, not video. So, they still need those old fashioned phones. (Bloomberg Businessweek - Bloomberg) Cell phones won’t be allowed on the sidelines until the NFL names an Official Cell Phone of the NFL. 
The sad part is, they’re probably taking bids for Official Cell Phone of the NFL right now :rolleyes:
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Cell phones are banned on sidelines, I believe.
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Can you hear me now? Hello? Can!? You!? Hear!? Me!? It can be unbelievably loud at field level, making cell phones utterly useless, but real phones can be had in varieties with extra-loud receivers and noise-cancelling microphones.
Verizon could always provide sound-proofed booths for cell phone use. There is already a company who makes one called the “Acoustibooth”.
I’d imagine coverage might be pretty bad when you have 60K people in one place, too. You’d hate to call the booth and have no bars.