National Emergency Alert Test
Simultaneous tests of the nation's wireless and broadcast alert systems will ping cellphones, TVs, and radios across the US today at 2:20 pm ET, the first such nationwide test since August 2021.
The less-than-one-minute alert—which can be deployed by only the US president or the head of the Federal Emergency Management Agency—is designed to evaluate the network's effectiveness in communicating national alerts within 10 minutes. The system has its roots in the Cold War when officials sought a quick way to warn Americans of a possible attack from the Soviet Union. State and local governments frequently deploy similar systems for weather alerts.
The cellphone notification will consist of a two-second tone followed by two one-second tones, a cycle which will be repeated twice, similar to Amber Alerts (listen here). Phones that are powered off, in airplane mode, or connected to the internet only through Wi-Fi will not receive the alert.