The Commerce Department's National Telecommunications and Information Administration, which is overseeing the effort, released detailed guidelines Monday.

Much of the concern surrounds the eligibility requirements for the $1.5 billion initiative, designed to help consumers purchase converter boxes that enable digital signals to be viewed in analog format.

Without such units, older analog-based televisions not connected to cable or satellite would go dark on Feb. 17, 2009 -- when the switchover occurs.

Consumers Union said it is worried that NTIA is limiting participation during a second phase of coupon distributions to citizens reliant on over-the-air reception.

The first phase would be open to everyone, including individuals and families who subscribe to cable or satellite service. Those households can receive digital signals via pay TV -- but often have extra analog sets that face going dark.

Jeannine Kenney, a Consumers Union senior policy analyst, said NTIA has settled on the strategy because it has limited resources.

"You can delay the [transition] date or adequately fund the program," she declared.

House Energy and Commerce Chairman John Dingell, D-Mich., and Telecommunications and the Internet Subcommittee Chairman Edward Markey, D-Mass., raised similar complaints.

"If the administration believes additional funds are needed to prevent consumers' television sets from going dark, then it should ask the Congress for such funding," Dingell said in a statement.

Markey echoed this concern, saying in a separate statement that the Bush administration "is evidently limiting the program in this way because of concern that sufficient funding to cover all consumers who need boxes may not be available."

An NTIA official said the agency wants to ensure that citizens who absolutely need vouchers can get them.

"We thought this was the most prudent approach" given that demand for the coupons is uncertain, the official said. NTIA Chief John Kneuer is tentatively scheduled to testify March 22 before Markey's panel.

Meanwhile, NTIA is not requiring manufacturers to make upgradeable converter boxes available under the program -- raising questions about obsolescence.

New guidelines issued Monday by NTIA "permit" manufacturers to offer coupon-eligible boxes that enable software upgrades. But such capability is not mandated.

Jason Oxman, spokesman for the Consumer Electronics Association, insisted that the "core function" of the boxes -- receiving digital signals and converting them to analog -- will not become obsolete.

Added an NTIA official, "Converters may be useful to some consumers for a long time."

But NTIA's parameters appear to fall short of demands made by Dingell and Markey in a November 2006 letter to NTIA.

"We suggest that NTIA also consider cost-effective measures to ensure that digital converter boxes have the capability to be updated, modified or repaired in circumstances where problems arise," they wrote at the time.

The NTIA official responded that industry stakeholders indicated that software upgrades are being field tested -- but are not commercially available.