Shelby County 911 now gets 60 to 70 percent of its distress calls from cell phones, said director John Ellison.

Sometimes, that can lead to problems.

“We were in a system where we knew where every phone was and its location,” Ellison said. “Now, every service provider is just different. You can be standing in the same yard and make two calls that will go two different places.”

Cell phones give off signals that show up on mapping devices at the 911-dispatch center, but even those can be inexact.

“You’re a dot on a map. We get your approximate position,” Ellison said. “Sixty-seven percent of the time, what you see on the map is within 50 meters of where the person actually is. Fifty meters is a pretty big area.”

Also, cell phone signals are not tied to any one address, but rather bounce off whatever tower is nearby. That can present headaches for 911 callers and dispatchers when calls are relayed to a dispatch center in the wrong county, Ellison said.

Because of that, cell phone users should be prepared with knowledge of what county they’re in as well as their approximate location.

“All the caller has to do is say, ‘I’m in Helena, I need Shelby County 911’ or ‘I’m in Calera, I need Shelby County 911,’” Ellison said.

Helena Fire Chief John Wilder said he’s seen some of these problems before.

“I’ve heard of instances where people will call with a cell phone and get Tuscaloosa County 911,” Wilder said. “It’s not a perfect system with regards to cellular phones because it depends on the cell tower. If you call from a cell phone, you need to know exactly where you are.”

Both Ellison and Wilder said those that own landlines need to do test calls to 911, especially if they’ve recently moved.

“If you change your phone company or your records, there could be human error,” Ellison said. “There’s always room for human error.”

If you’ve moved, wait five business days and then dial 911. Tell the dispatcher you’re making a test call and check to make sure you’ve gotten the dispatch center in the correct county.

For example, some Helena citizens live in Jefferson County but need their calls to go to the Shelby County 911 office, because Shelby County will dispatch the Helena Fire Department.

For more information, visit shelby911.org.