In an attempt to expand the nation's alert and warning system, Federal Emergency Management Agency officials are testing digital technology that can transmit text, voice and video messages simultaneously to wireless devices, radios, televisions and the Internet.

In early February, government officials successfully transmitted a text message to participating cellular, TV, Internet and radio providers who volunteered to participate in the test. In March, FEMA officials broadcast a bottomless audio message — a voice message of unlimited length — in the same manner. This month, they plan to test video streaming.

FEMA, which is part of the Homeland Security Department, is partnering with several agencies on the initiative, called the Digital Emergency Alert System pilot, part of the Integrated Public Alert and Warning initiative. The pilot, which is being conducted in the Washington, D.C., metropolitan area, is testing IP datacasting technology.

"What we want to do is almost a crawl, walk, run approach to this," said Reynold Hoover, director of FEMA's Office of National Security Coordination, referring to the series of tests. In each case, he said, FEMA officials are asking participants to provide feedback on how well they received the message, whether it was in the right format and whether they were able to re-transmit the message to their customers.

The one-year test project could determine how the president transmits future messages nationwide during a widespread emergency. But state and local emergency officials could use the digital technology on a daily basis to target encrypted, nearly instantaneous messages at authorized individuals in certain regions during emergencies.

During the tests, FEMA officials sent a digitally encoded alert and warning message to a public TV station, WETA, in Northern Virginia. In turn, WETA officials sent the message from their digital transmitter to participating companies, which were equipped with antennae and receivers hooked up to computers with commercial software. The messages were sent using the Common Alerting Protocol, an open standard for exchanging hazard warnings and reports.