<P> The system makes use of a combination of motion sensors mounted on the broadcast cameras to record what they are viewing, and / or the use of match moving computer graphics technology and an enhanced version of chroma key or "green screen" technology . </P> <P> (A competing system using different technology is called L - VIS for Live Video Insertion System .) </P> <P> The idea of creating an on - field marker to help TV viewers identify 1st down distances was conceived and patented in 1978 by David W. Crain, who presented the concept to Roone Arledge and Roger Goodman of ABC News and Sports and to the CBS Technology Center . At the time, both decided the broadcast industry was not ready to use Crain's invention . </P> <P> In 1998, ESPN programmer Gary Morgenstern and others revived the idea . ESPN's NFL coordinating producer, Fred Gaudelli, was tasked with overseeing an implementation for his network . The 1st & Ten line was first broadcast by Sportvision, a private company, during ESPN's coverage of a Cincinnati Bengals - Baltimore Ravens game on September 27, 1998 . A few weeks later, on Thanksgiving Day in 1998, Princeton Video Image (PVI) aired its version of the virtual yellow down line on a CBS broadcast of a Pittsburgh Steelers--Detroit Lions game . Four years later, SportsMEDIA introduced a third version during NBC coverage of a Notre Dame game . </P>

Who invented the first down line on tv