This Wednesday, November 9, the US Federal Emergency Management Agency [FEMA] will conduct a test of the national Emergency Alert System [EAS] at 2:00 PM EST. The test, the first ever, will affect all TV broadcast and cable channels, as well as radio stations; it is expected to last approximately 30 seconds. As the saying goes, Please Do Not Adjust your Set.
Ars Technica has a short article that discusses the test, and some of the steps that are being taken to ensure that folks realize that it is only a test. It also has a short sample video announcement (warning: it’s quite noisy!).