With Enhanced 911 (E911) service, the telephone number and physical location of the 911 caller are automatically displayed on the emergency dispatcher’s screen. This is unlike Basic 911 service, where the distressed caller has to tell the dispatcher where he or she is calling from. Enhanced 911 is crucial in circumstances where it is difficult or impossible for the caller to communicate his or her whereabouts, as the dispatcher is still able to send emergency response services to the correct location. Enhanced 911 also involves Selective Routing, whereby the 911 call is routed to the appropriate PSAP (Public Safety Answering Point) based on the caller’s physical location.

When 911 is dialed, a Public Safety Answering Point (PSAP) receives the call and dispatches fire, police, or medical services, depending on the nature of the emergency. PSAPs are generally controlled at the city or county level.

VoIP (Voice over Internet Protocol) is a communications technology for placing telephone calls over the Internet. Instead of sending phone calls over a physical phone line, VoIP works by converting voice calls into packets of data and sending them over an IP network. Because VoIP calls bypass a large part of the PSTN (Public Switched Telephone Network), VoIP phone service offers significant costs savings, especially for long distance calling. VoIP also offers a high level of mobility to its users: a VoIP phone number is not tied to a physical phone line, but rather can be plugged in anywhere there is an adequate internet connection.

An IP-PBX (Private Branch Exchange) is a VoIP telephone system for private enterprises. The IP-PBX connects an enterprise’s many extensions to the PSTN, but it also connects phones within the enterprise network, even those found in different regional offices. This allows enterprises to save on long distance charges, as inter-branch calls use the company data network and bypass the PSTN entirely. As IP phones operate over the enterprise data network, they can also support various communication applications such as directories or email clients.

With traditional phone service, each telephone number is tied to the phone line’s physical location. Since the phone number is static, location information only has to be entered into the ALI database once. IP phones and softphones, on the other hand, are nomadic: they work from anywhere with connectivity to the internet or to the company network. A VoIP phone could move from Florida to New York, for instance, and still keep its Florida telephone number. This poses problems for call routing, as 911 calls will go to the Florida PSAP rather than to the PSAP closest to the caller’s actual location in New York. It also means that the location last associated with the VoIP number in the ALI database may not reflect the phone’s current whereabouts.

Enterprises with centralized IP phone systems also experience problems with 911. When a branch office connects to an IP-PBX located at the main office, 911 calls will be transmitted to the PSAP serving the main office instead of going to the PSAP serving the branch office. In addition, because IP phones can move around easily on the company network while keeping the same phone number or extension, keeping track of each phone’s correct, up-to-date location information becomes extremely difficult. Advanced mobility features such as Shared Line Appearance and Extension Mobility only add to the difficulty in pinpointing a caller’s whereabouts.

ANI (Automatic Number Identification) is the automatic display at the PSAP of the telephone number associated with the line which called 911. Each telephone number and the physical location to which it corresponds are stored in an ALI (Automatic Location Identification) database, managed by the local carrier. In a 911 call, the PSAP uses the ANI to retrieve the caller’s physical address from the ALI database. Additionally, the ANI acts as a callback number should the PSAP lose its connection to the distressed caller. Both ANI and ALI are key capabilities of E911 service.

With traditional E911 service, ALI records are managed in a regional ALI database, usually administered by the local carrier. Anytime a phone number changes locations, the regional ALI is updated with the new location information. However, the nomadic potential of IP phones makes it difficult to ensure that the regional ALI is up-to-date. Whereas traditional telephone numbers are static, IP phones can relocate as they please – in fact, they can even relocate to a region served by a different ALI database. A VoIP service provider or enterprise would need agreements with each local carrier in order to update different regional ALI databases as the VoIP phone moved around the country. Because it is difficult for ALI databases to keep up with mobile VoIP users, there is no guarantee that the VoIP caller’s accurate location information will be available in a crisis.

In order to ensure up-to-date ALI for all VoIP users, no matter what their location, 911 Enable provides a single national ALI database (nALI) that maintains records from all 50 states. The service includes real-time address validation and correction, ensuring that the location data is valid and can be properly interpreted by the local PSAPs. For enterprises with branch offices in different regions, the nALI eliminates the complexity of managing records in different regional ALI databases, simplifying administration and reducing costs.

An Emergency Response Location (ERL) is a specific geographic location to which a 911 emergency response team may be dispatched. In a large enterprise, the PBX administrator may break down the campus or enterprise area into several different ERLs. This way, the PSAP is provided with location information which is more precise than simply the main address. For instance, each building on the enterprise campus, or floor or wing in the enterprise building, may be considered its own ERL, and within a given ERL there may be several phones or extensions. In some states, regulations require that enterprises maintain ERLs of specific sizes or identifiable areas (i.e. ERL per 1000 square feet or per floor).

ELINs are one way for enterprises to provide more specific location information to the PSAP. Enterprise administrators assign an ELIN (Emergency Location Identitfication Number) to each ERL. The ELIN is a 10 digit DID number purchased from the local carrier. One ELIN can be used for many phones within an ERL, but each ERL requires at least one unique ELIN. During a 911 call, the ELIN takes the place of ANI: it is used to route the call to the appropriate PSAP, and it corresponds with a specific ERL address that has been populated into the ALI database. The PSAP uses the ELIN to query the ALI database, and as a result is able to locate the 911 caller according to his or her ERL. Should the caller be disconnected, the ELIN can also be used by the PSAP to bypass the PBX attendant or auto-attendant and call back the extension directly.

PS-ALI (Private Switch Automatic Location Identification) provides E911 capabilities for phones in a PBX system. Generally, when a 911 call is made through a PBX, only the enterprise’s main address is sent to the PSAP. For enterprises spreading across several floors, or even several buildings, it can be very difficult for emergency response services to find the distressed caller based on the main address. By purchasing a PS-ALI account from the local carrier, enterprises can populate the regional ALI database with more specific location information. The 911 Enable solution is PS-ALI compatible, allowing enterprises to send automatic updates to the regional ALI database, or it can replace the need for PS-ALI accounts altogether through its national ALI database.