How do I register a VoIP phone for 911?

A 911 registration is a location record attached to your service. The FCC's name for what that record should produce is dispatchable location. The definition is the validated street address of the caller, plus additional information such as a suite or apartment needed to identify where the caller is.

The second half of that definition depends on the building. In a small single-story shop, the street address can be all responders need. In a ten-story office building, it isn't enough, and the floor or suite is the detail that gets responders to the right door.

For a service that can be used in more than one place, the rules also use the term Registered Location. It means the most recent information your provider has obtained that identifies your physical location. Under the E911 rule for VoIP, a provider that relies on a Registered Location has to obtain it from the customer before service starts. It also has to give you a way to update that location at will, and at least one update method must need only the equipment you already use for the service. The same rule sets which VoIP services must provide 911.

A Registered Location isn't the starting point for every softphone. The rule first asks the provider of a movable service for automated location where that's technically feasible. The registered address is one of the alternatives when it isn't.

For a desk phone at one address, Atlantech Online's static option puts the right address on the right phone number. You assign a specific address to each phone number in your account. Atlantech stores that address and sends it to the 911 call center, the public safety answering point, when the number dials 911.

The rule puts delivery on the provider. A fixed VoIP service must provide automated dispatchable location with each 911 call. With the static option, though, what gets sent is the address you assigned, so the accuracy of the record is yours to check.

Atlantech describes the static option as the simplest and most common one, and a good fit for a business in a fixed location. It also names two limits. The address has to be updated if a phone moves to a different location. And the static option doesn't support sub-address information such as a floor, suite or room number.

To correct an address, Atlantech's instruction is to open a support ticket, either by emailing support@atlantech.net or through its care site, with the relevant details.

Atlantech's second option ties the location to your network instead of to the phone number. It calls this the dynamic option, and it uses a format named PIDF-LO to carry location with the call.

You configure the location of each phone on your LAN switches and WiFi access points. A phone that dials 911 sends the location set on the switch or access point it's connected to. Move the phone from the second floor to the fifth, and the next call carries the fifth-floor location, provided the equipment there supports PIDF-LO and has that location configured. Atlantech says this option supports floor and suite detail, and that you no longer enter or update an address for each phone number.

The setup happens on your network, and Atlantech lists what it needs: equipment that supports PIDF-LO, correct configuration on that equipment, and a valid address for your network gateway. It also warns that a firewall or NAT device can block or alter the location headers. Atlantech offers to evaluate your network and guide the setup.

Microsoft Teams works on the same principle. Its documentation has an administrator load network identifiers into a location service and tie each one to an emergency location. The identifiers are subnets, WiFi access points, switches and ports. The Teams client then reports which one it's connected to.

A softphone on a home network is the hard case, because your office switches and access points aren't there to report anything. The federal rule covers this with the alternatives described above. If automated location isn't technically feasible, the provider can rely on a Registered Location that you're able to update. A provider that does so must identify when a 911 call comes from somewhere other than the registered address. It then has to prompt you for a new location or update the record itself.

Atlantech's article on nomadic E911 describes location that comes from the configuration of a WiFi hotspot or a network switch. For an employee working from home, settle two things with Atlantech support before anyone relies on a softphone there: where the home address is recorded and how the employee changes it.

The last step is to hear the record read back. Atlantech documents a 933 test for this. Dial 933 from the phone on Atlantech service, and a recorded message reads back your telephone number and then the E911 address set up for that phone. Some PBXs don't treat 933 as a valid number, so your PBX vendor may have to allow the call.

Suppose your 15-person office moves from a building in Silver Spring to the fourth floor of a building in Rockville and keeps its phone numbers on the static option. Each number still carries the Silver Spring address until the record changes. You send Atlantech the new street address for those numbers through a support ticket. Once the change is made, you dial 933 from a desk phone and listen for your number and the Rockville address.

The fourth floor won't be in that record, because the static option doesn't hold floor detail. If responders would need the floor to find you, that's the reason to look at the dynamic option.

The readback confirms the address registered to the number you called from. It doesn't show how a live call would be routed. If your phones use switch and access point locations, ask Atlantech how to check them.

Atlantech recommends repeating the 933 check every year. The same post describes a notification that emails one address of your choosing whenever someone dials 911 or 933, at no extra charge. You request it by emailing support with the address. With it turned on, check that inbox after your 933 call to confirm the alert arrived.