Answering questions about instant replay

On a booth replay challenge of Santonio Holmes' 4-yard catch with 50 seconds left in the Steelers' AFC North showdown against the Ravens on Sunday, referee Walt Coleman overruled head linesman Paul Weidner. After reviewing replays, Coleman ruled that Holmes had broken the plane of the goal line with the ball and awarded Pittsburgh a touchdown, giving the Steelers a 13-9 win and the AFC North title.

Ravens linebacker Ray Lewis and others thought Holmes didn't get the ball across the plane, sparking another debate about replay. Here are questions -- and answers -- about the hot topic:

Q: Why doesn't the NFL expand technology to include laser beams to determine if the ball or body crosses the goal line or GPS devices to triangulate certain areas of the field to rule on first downs and sideline and goal-line plays?

A: Cost is a factor, although that might not have been a topic for discussion a year ago. Because of the poor economy, the NFL is trimming about 150 employees, and franchises will trim staff over the next year. But let's put the economic issues aside for the moment.

The NFL has invested heavily in replay already. It has the latest in digital video equipment. It pays for officiating observers, a communicator, a replay judge in the booth and more. But it's unlikely it will try laser beams, computer chips in footballs or GPS devices. Whether the philosophy is right or wrong, what has to be understood is that owners, coaches and franchises are split on whether to have replay or not. Replay was voted out of the league once, and even though it's now a permanent fixture, support is always going to be split on how to advance the technology involved.

Q: Why doesn't the NFL consider using more cameras at all games?

A: The philosophy behind the current NFL replay system is the referee should only look at the views fans might see on television. That's why replay only uses cameras that are available to television. What the NFL doesn't want is the perception that there is some backroom secret camera view that determines calls.

Q: Why doesn't the league try to have the same number of cameras at all games?

A: Cost. The broadcast networks pay for the cameras and crews and they don't put as many cameras at a Lions-Chiefs game as they would at a Giants-Cowboys game, which would have a higher viewership. Also, prime-time games have much higher viewership, which translates into more sponsors, which translates into more revenue to provide for the extra cameras.

Q: As the 2008 season comes to a close, is there more scrutiny on calls even with the current technology?

A: Replay challenges are increasing as the season goes on. In the first 15 games of Week 15, there were 33 challenges, a season high. In Week 14, there were 27, which topped the previous season high of 25 in Week 13. For the season, there have been 285 challenges. So far, 108 calls have been reversed -- 30 were booth challenges by the officials and 78 were challenged by coaches. Last season, there were 323 challenges, and 94 (25 booth, 69 coaches) were overturned.

John Clayton, a recipient of the Pro Football Hall of Fame's McCann Award for distinguished reporting, is a senior writer for ESPN.com.