‘Presidential Alert’ Goes to Millions of Cellphones Across the U.S.

At 2:18 p.m. Eastern on Wednesday, cellphones across the United States emitted the ominous ring of an emergency presidential alert.

It was the first nationwide test of a wireless emergency alert system, designed to warn people of a dire threat, like a terror attack, pandemic or natural disaster.

“THIS IS A TEST of the National Wireless Emergency Alert System,” it read. “No action is needed.”

Two minutes later, televisions and radios broadcast test alerts. There was no notification plan for landlines.

The president — or someone he designates — would make the decision to send a real alert in case of a nationwide catastrophe, and the Federal Emergency Management Agency would push the button.

There is no opting out, which drew complaints on social media — and had already prompted a lawsuit.

Officials said before the wireless test they believed that it would reach about 75 percent of the roughly 225 million cell phones in the country, though they hoped the number would be higher.

Depending on your phone’s configuration and service provider, if you got the alert, your phone may have made a sound or vibrated, even if it was set to silent. People also received them at different times; it can take up to 30 minutes for the alerts to be transmitted to all devices.

Some things that could interfere: ongoing phone calls or data transmission, a device that is turned off or out of range, and smaller cellphone providers that are not participating in the program. It is not mandatory, but all the major cell phone providers did take part.

The test, originally planned for last month but delayed by Hurricane Florence, was the culmination of many years of work. The federal government developed a system to issue the alerts, which are scripted in coordination with numerous government agencies. They are limited to 90 characters, but will be expanded to 360 in the future.

The Communications Act of 1934 gives the president the power to use communications systems in case of an emergency, and a 2006 law called for the Federal Communications Commission to work with the wireless industry to transmit such messages.

The F.C.C. says the resulting Wireless Emergency Alert System has been used by local governments more than 40,000 times since 2012.

The law specified that the system should allow users to unsubscribe from local alerts about extreme weather or missing children. (Here’s how to turn them off, though officials warn against it.)

But the law also states that users cannot opt out of the presidential alerts, which are issued at the direction of the president — or someone he designates, or both — and executed by the Federal Emergency Management Agency.

That raised concern, given President Trump’s proclivity for sending impulsive messages on his favorite platform, Twitter. Users there had a lot to say about the alert on Wednesday afternoon.

And it has already spurred a lawsuit, filed in New York last week. The plaintiffs, three New York City residents, say that the alerts violate their free speech and amount to an unconstitutional seizure of their devices.