(FORTUNE Magazine) – Big Mo, a truck equipped with broadcasting equipment and topped by a 9-by-12- foot JumboTron giant TV screen from Sony, will have a starring role as the 105-year-old Texas State Fair beams into the video age this September. The $2 million contraption is the centerpiece of a network of at least a dozen oversize monitors that will blanket the 277-acre Dallas fairgrounds, feeding an expected 3.5 million visitors with event information, sports bulletins, music videos, and 20 minutes of advertising per hour. The system is the brainchild of Motion Graphics, a Dallas marketing firm that will charge advertisers $35,000 for one minute of Big Mo advertising per hour over the course of the 24-day fair. While Motion Graphics has yet to sign up any advertisers, the fair's corporate sponsors -- they include Exxon, Coca- Cola, Levi Strauss, J.C. Penney, and others -- will not leave the screen blank. Big Mo will broadcast events they sponsor at the fair, like the Oak Ridge Boys concert put on by Philip Morris's Miller Lite. In one sense, Big Mo is a 21st-century version of state fair tradition. In the early days, U.S. corporations often used fairs to introduce new products. But will 1991 fairgoers object to being bombarded with advertisements as they try to follow the sheep-shearing contest, judge the homemade quilts, jellies, and pies, or watch the nightly concerts in person? Jim Pemberton, the fair's vice president for marketing, doesn't think so. ''We are all kind of children of the tube,'' he says. Big Mo has also made the scene at other events, like car races and rock shows, and Motion Graphics is trying to line up more gigs around the country, state fairs included. - R.T.