WASHINGTON (AP) — Federal regulators Wednesday approved a plan to create a nationwide emergency alert system using text messages delivered to cell phones.

Text messages have exploded in popularity in recent years, particularly among young people. The wireless industry’s trade association, CTIA, estimates more than 48 billion text messages are sent each month.

The plan stems from the Warning Alert and Response Network Act, a 2006 federal law that requires upgrades to the nation’s emergency alert system. The act tasked the Federal Communications Commission with coming up with new ways to alert the public about emergencies.

“The ability to deliver accurate and timely warnings and alerts through cell phones and other mobile services is an important next step in our efforts to help ensure that the American public has the information they need to take action to protect themselves and their families prior to, and during, disasters and other emergencies,” FCC Chairman Kevin Martin said following approval of the plan.

Participation in the alert system by carriers is voluntary, but it has received solid support from the wireless industry.

Cell phone subscribers would be able to opt out of the program. They also may not be charged for receiving alerts.

There would be three different types of messages, according to the rules.

The first would be a national alert from the president, likely involving a terrorist attack or natural disaster. The second would involve “imminent threats,” which could include natural disasters like hurricanes or tornadoes or even university shootings. The third would be reserved for child abduction emergencies, or so-called Amber Alerts.

The alerts would be delivered with a unique audio signature or “vibration cadence.”

The service could be in place by 2010.

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