Get ready to hear an emergency alert test go off on your smartphone at 2:20 p.m. ET on Wednesday, Oct. 4 — but don’t panic.

Millions of us will hear the same test going off on all of our phones at the same time. It will also happen on TVs and radios.

The Federal Emergency Management Agency has announced it’s conducting a national test of the Emergency Alert System and Wireless Emergency Alerts on Oct. 4.

Info & FAQs:

The test will be accompanied by a unique tone and vibration on cellphones. The test message will read: “THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed.”

Those whose cellphones are configured in Spanish will receive the message in that language.

TV and radio broadcasters will also be required to deliver the test messages along with a similar audio alert tone to the ones they use in their monthly tests.

Why is it happening?

The purpose of the Oct. 4 test is to ensure that the nation’s emergency systems continue to be an effective means of warning the public about emergencies, particularly those on the national level, FEMA said in a statement.

“We recognize that in disasters, seconds count. Getting alerts out promptly to our communities saves lives,” Criswell said in her video.

FEMA is conducting the test in coordination with the Federal Communication Commission.

When should we expect it to happen?

The tests will begin at approximately 2:20 p.m. ET on Wednesday, Oct. 4. FEMA lists a backup testing date of Oct. 11.

Who will it affect?

All major wireless providers in the U.S. participate in Wireless Emergency Alerts and all of them will transmit the national test to their subscribers.

If your mobile phone is switched on and it’s within range of an active cell tower from a participating wireless provider, you should receive the national test.

Wireless providers will transmit the national test for 30 minutes, but your phone should only receive it once, per FEMA