Amber Alerts on Your Cellphones: What You Need to Know

[Editor's Note, Feb. 19, 2014: This post has been updated from the original published Aug. 6, 2013.]

It's an increasingly common occurrence: You're at home watching TV or out enjoying a quiet dinner when suddenly your cellphone lights up, vibrates and sounds a nerve-rattling alarm. It's all to announce an Amber Alert, and it can be extremely unsettling.

The automated cellphone alerts have been in place since Jan. 1, 2013, and were first used in California last August after a murder and kidnapping in rural San Diego County. In that case, a man was accused of killing a woman and her 8-year-old son, abducting her 16-year-old daughter, then fleeing with the teenager to Idaho. FBI agents shot and killed the suspect in that case, James Lee DiMaggio.

An Amber Alert issued while DiMaggio was believed to be driving his kidnap victim north was startling, to say the least. Craig Rosa, a producer for KQED Science, told us he was in his car with his wife when both phones started screaming "with an alert 10 times louder than any other alert on the phone. We had no idea what it was." It was especially loud since his wife's phone was connected via Bluetooth to the car's stereo.   "Almost ran off the road trying to shut the things off," he said.

Just last week, on Feb. 11, an Amber Alert was issued after an alleged carjacking and kidnapping were reported outside a Safeway in Oakland. It was canceled the next day after police concluded that the three people involved all knew each other and that a female adult had been mistaken for a teenage girl.

The system also can send out other types of alerts. For example, alerts were sent out on the East Coast to warn people during Hurricane Sandy.

Here's more from the Associated Press on the cellphone Amber Alerts and how to control them.

WHO GETS THEM?

Most people with newer phones have the emergency alert system automatically activated. The new Amber Alert system replaces a prior "opt-in" system that went offline Dec. 31 and alerted about 700,000 people who had signed up nationally.

The messages are geographically specific, going to people within the reach of a particular region's cell towers. So, a person vacationing in Los Angeles might receive a text, whereas someone with a California number visiting Boston would not.

Participating service providers include AT&T, Cellcom, Cricket, Sprint, Nextel, T-Mobile, U.S. Cellular, Verizon Wireless and Bluegrass Cellular, said Amy Storey, a spokeswoman for CTIA, a wireless industry association.

WHAT DO THE ALERTS LOOK AND SOUND LIKE?

They look like text messages but are free, and sent over a system administered by the Federal Emergency Management Agency.

The phone will go off with a high-pitched roughly 10-second tone and vibrate multiple times. The messages are limited to 90 characters. If you silence your phone the tone will not go off, but you'll still see the message on your screen.

HOW DO I TURN IT OFF?

To turn off the alarms on many phones, you can opt out under your phone settings or send a text message to your service provider. Contact your service provider for more details.