At a Super Bowl party, you’ll probably hear at least one casual football viewer ask, “How do they get that yellow first-down line on the field?” While “magic” is a fine answer in its own right, the real explanation is a bit more technologically intense.

Let’s have a look at the background and mechanics behind every football fan’s shining beacon, the yellow first-down line.

Actually, the first-down line's unlikely source is hockey. According to Allen St. John’s 2009 book The Billion Dollar Game, the first-down line actually emerged from the ashes of one of sports broadcasting’s bigger debacles: the FoxTrax system for hockey, which was designed by a company called Sportvision. FoxTrax – which hockey fans no doubt remember as the much-maligned “technopuck” that debuted in 1996 – employed a system of cameras and sensors around a hockey rink to place a little blue halo around the puck.

Still Confused? Check out this video for a better explanation.