ROSWELL, Ga. (AP) — In this era of active shooters, police shootings and global terrorism, a patchwork of technology around the country can make the experience of calling 911 vastly different depending on where you live.

More cities have begun to accept text messages recently, but the system that Americans rely on during their most vulnerable moments still hinges largely on landline telephones. That exposes a weak link that jeopardizes the ability of law enforcement to respond.

Experts worry that the nation isn't focused enough on improving the system and it is causing delays in getting emergency responders to the scene as fast as possible.

Recent examples include the Florida high school massacres where students had to whisper in calls to 911 or text their parents and had them call emergency dispatchers.