When U.S. TV signals switch from analog to digital in February 2009, as is mandated by federal law, the result could be staggering — for electronics manufacturers.

Millions of TV watchers are expected to need convertors in order to view the digital signals on their older model TVs. And the federal government is passing out vouchers to help pay for those boxes. It could add up to billions of dollars of sales for companies that design or build the convertors, a nice payday even if it’s just a one-time windfall.