How SIP Trunks Handle 911 Calls

e911 sip trunks

One of the most important phone numbers that you’ll ever dial (besides calling your mother – which you should do once a week) is 9-1-1.

When your phone is connected to a landline, and is one that you can physically see extending from your house to the phone pole on the street, you just don’t think about it much.

And why should you? It’s going on 50 years now since the first 911 call was made in the U.S. in 1968 by Senator Rankin Fite in Haleyville, Alabama. This occurred shortly after the FCC met with AT&T and Congress agreed to the proposal for a single emergency calling service and passed legislation.

On one hand we take it for granted that the call gets routed to the right place. On the other hand isn’t it reasonable to expect that a 911 call over VoIP should function exactly the same way?

VoIP and 911

Give the FCC page, VoIP and 911 Service, a quick read and you might be left with the impression of “caveat emptor.”

“Have a clear understanding of any limitations of your 911 service,” says the FCC and they provide a list that advises VoIP users that calls may not connect or properly connect to the PSAP (public safety answering point), calls may not work when the internet or power is down, and customers need to proactively provide their location and address information to their VoIP provider for 911 service to work properly.

However, in 2005 the FCC imposed VoIP regulations stating that, “providers of interconnected VoIP telephone services using the Public Switched Telephone Network (PSTN) meet Enhanced 911 (E911) obligations.”

As such, all customers who are using services as their primary residential or business telephone carrier must activate 911 Emergency Services on at least one of their DIDs.

Click here to read the full e911 terms and conditions.

911 Calls Over SIP Trunks When All Channels are Busy

Even when you’re using all of concurrent calling capacity some SIP trunking providers will give priority to a 911 or e911 call and let the call go through.

With other SIP trunks, the call will not go through if all channels are being used.

So on you’ll need to pick at least 1 enhanced DID per physical location. If you have a big building, for example, you’ll want to have one enhanced DID per floor.

The enhanced DID has the 911 certificate which attaches the address information to the call.

First you’ll need to program the outbound route for 911 which will override any caller ID you have on the trunk because it detects that you’re calling 911, and not a standard number like 867-5309.

We have instructions on how to setup an enhanced DID for e911 and how to test that the proper address and caller ID information is being displayed by dialing the test number of “933.”

For clarification:

[box type=”download”]Standard DIDThe lowest cost DID at where NO address information is input into our system[/box]

[box type=”download”]Enhanced DIDAn upgraded DID at where address information is input into our system which can be forwarded to a PSAP[/box]

The enhanced DID is key because it carries the address information that needs to be relayed to the 911 contact center. Standard DIDs are not meant for 911 calls. gets charged $75 for dialing 911 using a non-provisioned callerID number by our carrier – this charge then gets passed on to our customers.

In short, for the best 911 service on SIP trunks, buy at least one enhanced DID and in the long run you’ll save time, money, and lives.