Digital TV signals have sharper pictures, enable stations to broadcast more than one stream on the same channel and take up less spectrum than analog signals.

But the challenge is bigger than just converting signals to 1s and 0s: Manufacturers are now developing and building low-cost converter boxes, but retailers are yet to stock them. Consumers, meanwhile, are largely unaware they will need to buy and install one. The boxes aren't to go on sale until next January, 13 months before they will be needed.

"We have a lot of educating to do," said Jim Yager, who spoke on behalf of the National Association of Broadcasters.

To help consumers absorb the cost, Congress set aside $1.5 billion to subsidize converter box purchases. Every household, regardless of whether it needs a box, will be eligible to receive two coupons, each worth $40, that can be used to buy two converter boxes. The coupons, to be distributed on a first-come first-serve basis, must be requested between Jan. 1, 2008 and March 31, 2009.