Key Takeaways:
- NG911 deployment models take three forms: statewide ESInets, regional coalitions, and single PSAPs. A state can run one ESInet across every PSAP. A group of counties can pool procurement into a regional ESInet. Or an individual ECC can contract on its own. The model is often set by state 911 law and who holds the authority to levy, collect, and spend 911 fees.
- The NENA i3 standard is the shared architecture that lets statewide, regional, and local NG911 deployments work as one system. It defines every functional element of NG911, including how a call originates, how it routes, and how PSAPs transfer calls and share capacity across jurisdictions. How long a deployment lasts depends on how closely it holds to i3 at the boundary.
- Cross-ESInet interoperability depends on the i3 Forest Guide, the functional element that routes a 911 call when one ESInet can’t resolve the destination from its own data. The national Forest Guide is not yet operational, so inter-ESInet routing currently relies on bilateral coordination between adjacent providers. This makes “tested transfer success rate” the question that carries weight in procurement.
German mathematician Bernhard Riemann believed that somewhere inside a strange, imaginary function lay a hidden pattern that would reveal the precise location of every prime number in existence. Solve the function, and you’d hold a complete atlas of the most fundamental building blocks in all of mathematics. A century and a half later it remains unproven. What mathematicians discovered instead is that the standard is essential, even if the map itself is unfinished.
Hundreds of mathematical proofs now rest on the assumption that Riemann was right. Once you accept the hypothesis, the “music of the primes,” as one mathematician puts it, goes from chaotic to orderly. A common standard, even an unconfirmed one, gives every mathematician working in the field the same set of coordinates to work with.
Next Generation 911 (NG911) has its own organizing standard, with emergency networks scattering into seemingly unrelated shapes – a statewide ESInet here, a seven-county regional coalition there, or a lone rural center on its own contract. What lets them work as one system is NENA i3: the architecture standard that defines every functional element of NG911, from how a call originates and gets routed to how PSAPs share resources across jurisdictions.
Where Riemann’s hypothesis gave mathematicians a shared assumption to build on, i3 gives the emergency communications industry a shared architecture to build toward. Unlike Riemann’s line, this one is already drawn and already proven. The question is whether your NG911 deployment is built on this backbone.
Our first piece in this series laid out why NG911 modernization can no longer wait. The second showed how GIS data became the routing engine itself. This story explores shape: the forms a deployment can take, and the standard that lets them work as one. No single shape is the correct one for a Next Generation 911 deployment. Some states run a single statewide ESInet across every PSAP within their borders. Other regions pool counties into a coalition that procures one architecture together. Still, other individual ECCs sign their own contracts at the city or county level and operate alongside neighbors who chose differently. It’s critical to know that this isn’t just a decision point; 911 laws and who has the authority to levy, collect and spend 911 fees often decide the deployment model. In some cases, the ESInet may be deployed at a statewide model but the decisions around what call taking vendor to deploy is made at the ECC level. These decisions should be coordinated as there is a downstream impact to deployment decisions made at the network level.
All three are in production today on INDIGITAL infrastructure. Whether any of them lasts twenty years or deprecates in five comes down to the standard they sit on.
The Statewide Model: Built to Last
A statewide NG911 deployment is ultimately a governance contract: one that outlasts carrier sunsets, legislative cycles, even the tenures of the people who signed it. The problem is keeping hundreds of agencies aligned on one architecture across decades. That kind of continuity can’t be promised, but it can be demonstrated.
Six states run their entire NG911 backbone on INDIGITAL infrastructure: Alabama, Indiana, Michigan, New Hampshire, Rhode Island, and Vermont. Vermont has operated on INDIGITAL since 2015 at five-nines availability. New Hampshire has been statewide since October 2015. Indiana has carried IP-based 911 since 2006, including the state’s first wireless 911 calls – a deployment built when NENA was still in the process of defining the i3 standard it would eventually require. We don’t look at these as contract wins. Rather, we continuously measure each relationship in years of answered calls.
Indiana’s Q3 2025 snapshot (827,304 calls processed, 524,103 handed off to AT&T across IP NNI, Texty active in 113 agencies, MEVO deployed in every primary PSAP) is the kind of record a renewing 911 Board can actually evaluate. It is the same template replicated across Alabama, New Hampshire, Rhode Island, Vermont, and Michigan.
What ties them together architecturally is independence from any national cloud controller. Each runs on private, region-anchored infrastructure with dual Node A/B redundancy, in-state operational presence, and a 24/7 Network and Security Operations Center. That’s not a marketing line, either. At three in the morning, when a tornado warning is active, the difference between a five-minute fix and a five-hour outage is whether a knowledgeable engineer answers the phone.
The Regional Model: Coalitions That Work
Between the statewide ESInet and the single county sits a third, increasingly consequential pattern: the regional ESInet. A coalition of counties pools procurement, governance, and operational support to reach NG911 sooner, and cheaper, than any member could alone. The model works when the counties stay coordinated.
Take the South Carolina Coastal Area Cooperative for example; Charleston, Beaufort, Berkeley, Florence, Horry, Goose Creek, and Summerville share one architecture, one operational provider, and one set of governance documents. INDIGITAL provides the ESInet and Next Generation Core Services across all members while each jurisdiction keeps full local control of its own dispatch.
The geography of the region reinforces the logic of the arrangement. Hurricanes don’t observe county lines, and the Cooperative’s round-robin design distributes overflow calls among members so no single center is swamped during a regional event. Shared procurement also commands stronger terms than any county could negotiate independently, and a coalition 911 authority can file a single Phase 1 and Phase 2 request for all eight PSAPs at once rather than running eight separate proceedings. As of Q1 2026, six member PSAPs are live end-to-end, covering more than 28% of South Carolina’s population and processing 162,908 calls in the quarter.
Coalitions succeed when members agree on one technical standard (NENA i3), one operational provider, and one set of governance documents. Coalitions that compromise on any of those three tend to compound the problem. For instance, counties that cling to incumbent vendors end up stitching incompatible architectures together with point-to-point translators, trading the efficiency they joined for to preserve a legacy relationship they should have ended.
Where the Regional Model Crosses State Lines
In 2020, Charleston County chose INDIGITAL for its move to NG911. After Helene, Ian, and Debby, Collier County, Florida wondered whether they could route calls to Charleston County through a sustained outage. But there was a complication: Charleston’s core services ran on INDIGITAL, Collier’s on Motorola. Long-distance mutual aid would demand clean interoperability across vendor lines. INDIGITAL took the lead in building and testing it.
The arrangement went live on Oct. 30, 2024, with Collier’s 911 calls answered by Charleston telecommunicators, then tested again in the opposite direction on March 13, 2025. As Bob Finney, ENP, of the Collier County Sheriff’s Office put it, “The person calling doesn’t know which county is answering the call. It was flawless.”
Two state networks, two NGCS vendors, and one geographically diverse mutual-aid arrangement, made possible because both deployments were built to a shared standard. As Finney put it: “What this has done is just the beginning of interoperability on a national level, showing it can be done.”
The Local Model: Backbone of the Nation
Every layer of NG911 exists to do one thing: deliver a 911 call to a telecommunicator who can send help. Interoperability is how that happens when the call crosses a boundary between counties, between states, or between vendors. Regional interoperability lets a coalition share capacity during a surge. PSAP-to-PSAP interoperability lets one center cover another when it goes down. Both depend on the same thing: a shared standard at the foundation.
INDIGITAL provides Next Generation Core Services (NGCS) to individual PSAPs in Florida, Illinois, Kentucky, Missouri, and Ohio, each under its own contract. Florida has the largest footprint: 40 of 67 counties, 24 with Phase 2 location-based routing complete, and 769,374 calls processed in Q4 2025 alone. None of those PSAPs share a contract, yet all of them run on the same architecture.
Lenawee County, Michigan shows what that means in practice: a single ECC of 19 telecommunicators serving nearly 100,000 people, and running on the same platform as Indiana’s statewide deployment. It scales down further to cover a NASCAR race through a MEVO Anywhere Kit, a complete call-handling system in a hardened case deployable by two people from a vehicle. The configuration looks nothing like a statewide build, but the standards that govern it are identical.
Where Local Control Creates a Problem: The Forest Guide
Local control introduces a challenge procurement officers rarely meet until they’re staring it in the face. When neighboring PSAPs in the same state run on different core-services providers, a call placed at a jurisdictional boundary has to cross from one ESInet to another without losing the call, the location, or the seconds that matter. Florida shows it plainly, with five providers across 67 counties, and a caller on a county line may need a PSAP in the next provider’s territory.
The i3 standard answers this with a functional element called the Forest Guide. Each ESInet’s routing function keeps a “tree” of its coverage; the collection of every tree in the country is the “forest.” When one ESInet cannot resolve a call’s destination from its own data, it queries the Forest Guide, which finds the ESInet that owns the location and routes the call there. Without it, boundary-crossing calls misroute or fall back to the legacy router and lose their location data. As NENA puts it, each jurisdiction becomes an island.
However, the National Forest Guide is not yet operational. NENA published the requirements in 2014, and until a sponsoring entity completes that procurement, inter-ESInet routing depends on bilateral coordination between adjacent providers.
So asking a vendor whether it “supports Forest Guide” settles nothing – every i3 vendor will say yes. The questions that carry weight are operational: which neighboring ESInets is your Forest Guide indexed against today, what are the documented demarcation points, and what is your tested transfer success rate for inter-ESInet calls?
One Standard, Whatever the Shape
Whatever form a deployment takes (statewide, regional, or county) it holds together only to the degree it sits on the standard at the boundary. Riemann’s hypothesis gave mathematicians a shared assumption to build on even before it was proven. NENA i3 gives the emergency communications industry something much rarer: a shared standard that is already proven, already deployed, and already working. The discipline is in holding to it.
The next piece in this series examines what a deployment does when disaster arrives, and why a portable, self-contained 911 system now belongs at the core of the architecture.
Curious to learn more? INDIGITAL will be at NENA 2026 later this month. Stop by the booth to see a MEVO Anywhere Kit deployed live and to map a statewide, regional, or single-PSAP path to NG911 for your jurisdiction. Reach out before the show to book a meeting or floor demo.
Subscribe to The 911 Wire to follow the rest of the series.
Frequently Asked Questions (FAQ)
The NENA i3 standard is the architecture that defines every functional element of Next Generation 911 — from how a 911 call originates and routes to how PSAPs transfer calls and share resources across jurisdictions. Published and maintained by the National Emergency Number Association, i3 is the shared framework that lets statewide, regional, and local NG911 deployments work as one interoperable system.
NG911 is deployed in three primary models: statewide, where a single ESInet serves every PSAP in a state; regional, where a coalition of counties shares one architecture and governance structure; and local, where an individual PSAP or ECC contracts on its own. The model is often set by state 911 law and the authority to levy, collect, and spend 911 fees. All three run on the same NENA i3 architecture, which is what lets them interoperate.
Yes. When two NG911 deployments are built to the NENA i3 standard, calls can transfer between ESInets and across state lines even when the two systems run on different core-services vendors. In 2024, INDIGITAL built and tested cross-state mutual aid between Charleston County, South Carolina and Collier County, Florida — two separate networks on two different vendors — with calls answered seamlessly in both directions.
The Forest Guide is the i3 functional element that routes a 911 call when one ESInet cannot resolve the destination from its own location data. Each ESInet’s routing function keeps a “tree” of its coverage area; the national collection of those trees is the “forest.” NENA published the Forest Guide requirements in 2014, and until a national Forest Guide is operational, inter-ESInet routing relies on bilateral coordination between adjacent providers.
An i3-compliant NG911 deployment implements the functional elements NENA i3 defines — including the ESRP, ECRF, and BCF — and can route, transfer, and share calls with any other i3 system at the boundary. Compliance shows up in operation: the questions that carry weight are which neighboring ESInets a provider’s routing is indexed against, the documented demarcation points, and the tested transfer success rate for inter-ESInet calls.