The vouchers will reduce the cost of converter boxes that will enable older television sets relying on over-the-air reception to function after the Feb. 17, 2009, transition. The $40 vouchers will be available online, via the mail and through a toll-free number, lowering the cost of each unit from about $60 to $20.

The announcement was made amid a growing drumbeat of criticism from Democratic lawmakers and regulators, as well as watchdogs, that the transition could be a "train wreck" if consumer outreach is not expanded. NTIA spokesman Todd Sedmak responded that considerable planning is underway behind the scenes and that the switchover is still 18 months away.

NTIA, which is part of the U.S. Commerce Department, is spending $5 million to reach populations most at risk of having their TV signals halted: the disabled, elderly, low-income citizens, minorities and rural Americans.

To do so, it is partnering with associations such as the seniors' group AARP, the American Library Association and the food-stamp program on educational efforts. The FCC has requested an additional $1.5 million to assist with consumer outreach.

But NTIA is relying solely on networks and local stations to run TV and radio ads about the transition and the coupons.

Last week, Sen. Claire McCaskill, D-Mo., a member of the Senate Commerce Committee, sent letters to the FCC and the NTIA expressing concern about the apparent lack of public education and awareness. She also sought feedback on how well the boxes function and on their anticipated availability in stores.

The federal government will take several steps this fall to get the transition back on track. NTIA will hold a public DTV meeting and expo on Sept. 25 featuring the chief executive officers of the major broadcast, cable and electronics associations, among other participants.

On Sept. 26, the FCC will hold a daylong consumer education workshop to explore the challenges associated with the changeover.

And Sen. Daniel Inouye, D-Hawaii, the Senate Commerce Committee chairman, has pledged to hold another DTV oversight hearing this fall.

On Aug. 2, David Rehr, president of the National Association of Broadcasters, sent a letter to senators informing them of steps that his association is taking to ensure a smooth transition. He also revealed that industry-sponsored public-service messages will be available for airing beginning in December.