The Federal Emergency Management Agency and the Federal Communications Commission will hold the first national test of the Emergency Alert System.
For 30 seconds beginning Wednesday at 2 p.m., "this is a test" will be broadcast on radio, TV and cable stations, satellite radio and television services, and wireline video service providers across the country.
The national alert and warning system was established to enable the president to address the American people during emergencies and disasters. The system never has been tested nationwide.
The National Weather Service, governors and state and local emergency officials also can use aspects of the system for localized alerts.