This is from the Homeland Security Website, in part:



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Emergency Alert System
Certified EAS Equipment Vendors
State EAS Plans and Chairs
You're at: FCC / PSHSB / Policy Areas / Emergency Alert System
Emergency Alert System
Releases
EAS Handbooks
EAS Archives
The EAS is a national public warning system that requires broadcasters, cable television systems, wireless cable systems, satellite digital audio radio service (SDARS) providers, and direct broadcast satellite (DBS) providers to provide the communications capability to the President to address the American public during a national emergency. The system also may be used by state and local authorities to deliver important emergency information, such as AMBER alerts and weather information targeted to specific areas.

The first Nationwide test of the Emergency Alert System will be carried out on November 9, 2011. For more information about the test or access to the participant reporting system, please click here.

The FCC, in conjunction with Federal Emergency Management Agency (FEMA) and the National Oceanic and Atmospheric Administration's National Weather Service (NWS), implements the EAS at the federal level. The President has sole responsibility for determining when the EAS will be activated at the national level, and has delegated this authority to the director of FEMA. FEMA is responsible for implementation of the national-level activation of the EAS, tests, and exercises. The NWS develops emergency weather information to alert the public about imminent dangerous weather conditions.

.................the rest of this can be read at: Emergency Alert System (EAS) | Public Safety and Homeland Security Bureau