[Al Skierkiewicz]

Bob,
If you remember back a few years, the TV networks began using a tracking system to follow the puck in a hockey game. That system used IR LEDs around the perimeter of the puck. Each venue was wired with receptors to determine where the puck was in a grid like fashion. With that data in hand, pan, tilt and zoom data were then extracted from each camera and processed by a computer that then positioned a "hole" in the video output of the system which was then filled and "streaked" to make the puck more visible. That system has gone on to produce the now famous "green" first down mark on football coverage. If you watch football you will notice that not all cameras will show the first down marker since all cameras are not wired to send data to the position computers.