How is the NFL replay system set up? I am assuming that the
NFL replay booth has their own set of replay machines and each machine just takes a different camera feed from the broadcast truck. I would assume and hope that the officials replay booth does not have the broadcast program video and audio. How many replay machines do the referees have? Do they each have slo-mo capabilities or just real speed playback? Anybody know for sure?

Have slo-motion
 

They have slow motion capabilities and I believe the Referee on the field can control the replay speed. I'm pretty sure the replay booth has access to all of the replays from several different cameras.

I believe - I could be wrong - that the Referee is limited to reviewing only those replays that have been shown to the public before the challenge. Even if other angles become available and are shown to the viewing public during or after the challenge, they are not included in the review. The NFL uses TV feeds and has no extra or special cameras for replay.

I think I read that somewhere.

That's not exactly how it works.

The system begins with the replay booth receiving a "live" feed from the network television control truck covering the game.

The four individuals in the replay booth will be the "replay assistant," "technician," "video operator" and "communicator." The replay assistant is the direct and only link to the referee on the field.

The "technician" in front of the live-feed monitor cues up the live play by pressing the "make play" button on his console as the ball is snapped. That automatically puts the play on a "touch-screen monitor" positioned in front of the replay assistant. When a replay comes up from the truck, the technician presses a "make replay" button and that automatically pops up on the touch-screen monitor. The monitor can accommodate six replay angles of a single play.

The "replay assistant" is positioned in front of the touch-screen monitor. This person decides which replays will be relayed to the field monitor for review by the referee after a coach's challenge is issued, and whether an official's time-out will be called for a play review in the final two minutes of each half and overtime.

The "video operator," at the instruction of the replay assistant, will tap the touch-screen monitor (similar to a bank's automatic teller machine that prompts commands by the tapping of its screen) to transfer one of the replays to the booth's third monitor that is positioned between him and the replay assistant. The video operator can control the speed of the playback on this monitor by the turn of a dial. This is the monitor on which the replay assistant will view all replays. The video on this monitor is what the referee on the field will see.

The "communicator" is the replay booth's "eyes to the field." While the technician, replay assistant and video operator are doing their jobs, the communicator, stationed in back of the other three, is watching the field. He will advise the replay assistant — who is busy viewing the monitor — that "they're in the huddle," "they're on the line" and "the ball is snapped" so the replay assistant will know that the next play has started, negating the possibility of a replay. He will also report to the replay assistant if an official ruling (e.g. holding, illegal procedure, etc.) has been made on the field following a play that might eliminate the need for a replay.

The communicator also is the timer of the 90 seconds allocated to the referee to make a decision on a replay. Once 90 seconds are reached, the communicator will hit a red button on the console in front of the replay assistant that will automatically shut off the field-level monitor, signaling to the referee that the 90 seconds has expired and the review is over. The referee must then announce his decision.