methods for accurate transmission of elin / callback number from an emergency caller calling from behind a pbx / mlts include prioritizing the emergency call , assigning a port equipment number to each device / trunk of the pbx / mlts and associating ports / devices with elins and callback numbers . the apparatus of the invention detects an emergency number , assigns the call priority , and uses the port / device number to determine the elin / callback number and properly transmit the elin / callback number .