WASHINGTON — Senators yesterday blasted the government's efforts to tell millions of people who rely on antennas to watch TV that their sets may go blank in a little more than 18 months, when broadcasters switch to digital-only signals.

"I think there's high potential for a train wreck here," Sen. Maria Cantwell, D-Wash., told Federal Communications Commission and Commerce Department officials during a hearing on the digital TV transition.

Lawmakers and advocacy groups have become increasingly concerned that the government isn't doing enough to educate the approximately 20 percent of households that receive only over-the-air TV.

Under federal law, stations must turn off their old analog signals Feb. 18, 2009, and broadcast only in digital.

Although cable and satellite systems have promised to convert the signal for old analog TVs, those without new digital sets will need special converter boxes.

Democrats appear poised to push for more money and public service announcements to prepare TV owners. U.S. officials have budgeted $5 million to tell people about the switch and the free coupons that will be available on a first-come, first-served basis to cover most of the cost of a no-frills converter box.

The government is relying on the television industry and consumer electronics makers to do the bulk of the public education, and so far "their efforts have yielded few results," said Senate Commerce Committee Chairman Daniel K. Inouye, D-Hawai'i.

A survey released in January by the Association of Public Television Stations found that 61 percent of respondents were unaware of the pending digital switch.

"We really do have a long ways to go in this process," said Sen. Olympia J. Snowe, R-Maine.

COUPONS AVAILABLE

Government officials said funds were limited but that they expected awareness to rise as public and private education efforts ramped up.

"We have more work to do," said John Kneuer, assistant secretary for communications at the Commerce Department, which will run the $1.5 billion converter box coupon program.

The coupons will be available Jan. 1. Federal officials have set up a Web site, DTV.gov, and a toll-free number, 888-DTV-2009 (388-2009), to answer questions.

Inouye Wednesday promised to take action on the public education effort after listening to complaints from the Leadership Conference on Civil Rights, the National Hispanic Media Coalition and AARP, the organization for seniors. The groups are concerned that poor and isolated people will be disproportionately affected.

Inouye did not say what steps he was considering.

FCC Chairman Kevin J. Martin has requested $1.5 million from Congress for additional outreach.

Congress also may press broadcasters to do more to educate TV viewers through public service announcements. Reps. John D. Dingell, D-Mich., and Edward J. Markey, D-Mass., have suggested that the FCC consider requiring TV stations to run those announcements.

ANNOUNCEMENTS DUE

The National Association of Broadcasters is creating several public service announcements and will devote free airtime worth tens of millions of dollars starting in December, said Dennis Wharton, the trade group's executive vice president.

He noted that broadcasters had the most at stake if people couldn't watch their stations.

"There's no question there's a staggering lack of information about this transition, and it's our job to try to correct that," he said.