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Amber Alert: Why mobile phone users got urgent missing-child texts

Cellphone and smartphone users across Southern California received Amber Alert

Mobile phone users across Southern California received an Amber Alert for a missing boy on Friday.

The widespread alert is part of a new system that California adopted last year and has used several times.

On Friday the alert was issued after a 2-year-old was allegedly abducted by his father.

Police were contacted around 6:30 a.m. by the child’s mother, who said an ex-boyfriend, Abraham Vargas, 26, had taken the boy and the family's orange Nissan Quest from the 1000 block of South Lorena Street in Boyle Heights.

There was damage to the right side of the vehicle's body, and Vargas may be heading to Mexico, according to an alert from the Los Angeles Police Department.

Vargas was under a court-issued restraining order barring him from contact with the mother, Los Angeles police Officer Norma Eisenman said.

Authorities said the boy was wearing a red sweat shirt and blue sweat pants. The Nissan’s license plate number is 7CIN189.

Here are some facts about the new Amber Alert system:

What is it?

The Wireless Emergency Alert is a new program for mobile phones that started Jan. 1, replacing the previous “opt-in” system.

Phone owners now receive messages automatically, based on their proximity to the emergency, not based on their phone number.

How does it work?

An alert that looks like a standard text message reaches a user's phone based on a number of criteria.

People who said they never got an alert, or received more than one, should keep in mind that messages are disseminated through cell towers, not phone numbers. And since cell towers to be used are determined on the basis of geographic proximity to the incident, it’s possible that moving between affected zones can result in your phone receiving multiple messages.

The signal is transmitted simultaneously to all mobile devices within the range of cell towers in the affected area. Authorities also broadcast the alerts multiple times, to account for the movement of people in and out of these zones.

There are no texting charges, and the system does not track phones' whereabouts.

Can I opt out?

All newer models of mobile phones come wired to automatically receive the alerts.

To opt-out of the emergency alerts, change your phone's settings for emergency alerts.

Copyright © 2015, Los Angeles Times