California's AMBER alert system aided police in the rescue of two teenage girls who were kidnapped at gunpoint Thursday morning.

The system, in use by many police departments across the country, often means the difference between life and death in a kidnapping case.

The full name of the AMBER Plan is America's Missing: Broadcast Emergency Response and it's an emergency broadcast system to help find missing children. Created in 1996, the system is a voluntary partnership between law enforcement and broadcasters to activate urgent alerts to the public in serious child abductions.

The system is a powerful legacy of 9-year-old Amber Hagerman, who was kidnapped and murdered in Arlington, Texas. Before the two girls were found alive and well in California Thursday, the system had saved at least 18 kids.

When police are sure a child has been abducted, they notify the media to issue a bulletin. That way, anyone who has seen or heard anything about the suspect can notify authorities.

Once law enforcement has been notified about an abducted child, they have to determine if the case meets the AMBER Plan's criteria for triggering an alert. Police must be sure the child has been abducted, must be certain the child is in danger of bodily harm or death and there must be enough descriptive information about the child, abductor and/or suspect's vehicle.

If all these criteria are met, alert information containing as much detail as possible is put together for public distribution, then faxed to those radio stations that are part of the Emergency Broadcast System. The stations send that information to other area radio, television and cable systems, which then plaster pictures and other information across their broadcast.

Timing is everything, since missing children's groups estimate that in three-fourths of child abductions, the child is killed within three to four hours.

But a growing number of states that have statewide systems -- including Arkansas, Florida and Oklahoma -- are hoping it will help locate missing kids before it's too late.  The California Senate on Tuesday will debate a bill making the system used to rescue the two teenage girls statewide.

"There are 3 million people here ... at any given time, approximately 100,000 are listening to radio or television, that's a hundred-thousand eyes and ears looking for one child," Greg Feldman, assistant chief of the South Miami Police Department, recently told Fox News. "The chances of us finding this child safely go up dramatically."

But the AMBER Plan may not be the answer for every missing child case. Law enforcement officials have said they won't use the system to find runaways or parental kidnappings but they save the alert for kids taken by strangers.

According to the National Center for Missing and Exploited Children, the program's popularity has been sweeping across the United States and into Canada. Since the original plan was set up in 1996, 41 modified versions have been adopted at local, regional and statewide levels.