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NG9-1-1 Overview

Upgrading from traditional analog 9-1-1 systems to the Internet Protocol (IP) based technology of NG9-1-1 will enhance the speed, reliability and responsiveness of emergency services.

For 50 years, the 9-1-1 system has served the needs of the public in emergencies. Next Generation 9-1-1 (NG9-1-1) will create a faster, more flexible, resilient, and scalable system that will keep up with the communication technology used by the public.


The basic element of the i3 architecture is an Emergency Services IP network (ESInet), designed as a network of networks that can be shared by all public safety agencies involved in an emergency. No longer are PSAPs isolated from one another, or only connected to other PSAPs that share the same selective router. They can communicate digital information (e.g., voice, photos, videos, text messages) with each other seamlessly over the ESInet using a common communications protocol.


In addition to designing an all IP-based telephony system with a corresponding IP-based ESInet, the i3 architecture includes a significant change in how calls are routed to the PSAP. In a legacy 9-1-1 system, the master street address guide (MSAG) groups street segments into Emergency Service Zones (ESZ), and each zone is assigned a unique Emergency Services Number (ESN) identifying the primary PSAP for that zone. The selective router uses this information to route the call to the PSAP. When the call and its corresponding Automatic Number Identification (ANI) are received, the ANI-ALI controller initiates a query to the automatic location information (ALI) database, which associates the caller’s telephone number with the location information and provides the location to the PSAP.

In NG9-1-1, GIS replaces the MSAG in the form of a Location Validation Function (LVF) and Emergency Call Routing Function (ECRF). The ALI database is replaced by the LDB (Location Database) or LIS (Location Information Server). All customer address records are validated against the LVF, as the ALI was against the MSAG. The ECRF will route a 9-1-1 call by determining which PSAP’s geographic service area (polygon) correctly matches the caller’s civic address or geo-coordinates.

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