WASHINGTON (AP) — Electronic devices across the United States sounded off Wednesday as the Federal Emergency Management Agency conducted its first-ever national wireless emergency alert test.

The tone went off at 2:18 p.m. EDT. The subject of the alert read: "Presidential Alert" and text said: "THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed."

FEMA officials estimated that about 225 million devices would receive the alert at about the same time, but the message was broadcast by cell towers for 30 minutes so some people got it later than others. Some got as m...