By law, it is the responsibility of local governments to establish the infrastructure for 911 service. This means they need to organize the districts and organize and staff the PSAPs, as well as collect surcharges to pay for the service.

The Incumbent Local Exchange Carrier (ILEC) fills the role of installing and managing the systems that route 911 calls and information to the right locations. In the areas we cover, BellSouth is the ILEC. Today, we serve approximately 400 local governments and 800 call centers in the Southeast.

At its core, the 911 system is a wireline system. When a wireline phone establishes an open line to the outside, it is communicating with a local exchange carrier switch. The digits transmitted to this switch tell it where to send the connection. More than 20 years ago, BellSouth was one of the first to implement call routing technology that sends 9-1-1 calls to the correct PSAP. This was accomplished by adding a tandem switch to the 911 network.

This BellSouth 911 tandem is a central switching center that routes the Automatic Number Identification (ANI) and the caller's voice over a trunk line to the appropriate PSAP. A 911 tandem can be responsible for several PSAPs.

What about wireless calls? The only difference here is that the original connection is with a wireless provider's tower. This tower is supported by a mobile switching center that sends any 911 call to the appropriate 911 tandem. Even with the advent of wireless 911, BellSouth is still responsible for that "last mile" to the PSAP.