From www.ready.illinois.gov:

Radio and TV stations across the nation will participate in the first-ever nationwide test of the Emergency Alert System at 1 p.m. CST on Nov. 9. The three-minute test will be conducted by the U.S. Department of Homeland Security's Federal Emergency Management Agency (FEMA), the Federal Communications Commission (FCC) and the National Oceanic and Atmospheric Administration (NOAA).

"The Emergency Alert System is an important tool for providing critical information to the public during emergencies," said Jonathon Monken, director of the Illinois Emergency Management Agency (IEMA). "This nationwide test is a very ambitious and necessary step to ensure the viability of the system."