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Emergency Calling for SIP Trunking

Twilio’s Emergency Calling for SIP Trunking feature enables emergency call routing to Public Safety Answering Points (PSAPs) in the US, Canada, and the UK.

In the US and CA, Twilio supports both Enhanced 911 (E911) as well as Basic 911.

E911 calls are routed to the PSAP serving the address associated with the phone number that made the call. The call automatically includes the caller’s Twilio phone number and corresponding address information to the 911 dispatcher answering the call.

Basic 911 calls are routed to the designated PSAP serving the address associated with the phone number that made the call. With Basic 911, the dispatcher answering the phone will not have access to the customer’s phone number or address unless the caller provides this information verbally during the call.

Certain Twilio phone numbers will not have access to either Basic 911 or E911 services. In that case, 911 calls will be routed to a national emergency call center. A trained agent at the emergency call center will ask for the caller’s name, phone number, and location. They will then transfer the caller to the appropriate local PSAP or otherwise determine the best way to provide emergency services.

In the UK, Twilio supports both 999 and 112 emergency numbers. The emergency calls are routed to the PSAP serving the address associated with the phone number that made the call. When an emergency call is made, the corresponding address information and caller’s Twilio phone number are automatically provided to the dispatcher answering the call.

You can configure Emergency Calling in the Console as outlined below, or via the API.

To enable Emergency Calling from a Twilio phone number

  1. Associate an address with your emergency calling capable Twilio phone number. Do this from the Numbers tab of your Trunk or from the phone number configuration page. Addresses will be validated before they can be added.
  2. Enable Emergency Calling for that number.

Emergency calls will only be routed when Twilio phone numbers enabled for Emergency Calling are used as the Caller ID (the SIP From: header). Emergency calls from any other number will be rejected.

You must then ensure that

  • Any emergency call must come from a Twilio phone number enabled for Emergency Calling (identified in the SIP From: header).
  • You configure your Trunk’s Origination Setting appropriately. This is important in case the emergency responder needs to call you back.

You configure Emergency Calling under the Numbers tab of your Elastic SIP Trunk, or on the number’s configuration page in the Console’s Phone Numbers section.

Associate an address with your Twilio phone number

At the Numbers tab of your Trunk, or on the phone number’s configuration page, click Enable for the number you want to be able to make emergency calls.

If this is your first time using emergency calling, you will need to add an address to your account. This address represents the physical address used to direct police, fire, medical, and other emergency response resources. In the US and CA, the address must be recognized by the Master Street Address Guide (MSAG) database. Each address created may be used for any phone number associated with your Trunk(s).

In the US, the MSAG address will often differ from the equivalent US Postal Service address because the MSAG uses the community name (township, city, county) from where the closest responding PSAP will come.

Input your address and then click Save & Continue. If your address can’t be validated, you will be asked to select one of a number of suggested alternatives. The address you provide will then be associated with the Twilio phone number(s) you selected. If you need any assistance with address validation, please contact our support team.

Enable Emergency Calling on the Twilio phone number

Once you’ve associated a valid address with a Twilio phone number, you may enable Emergency Calling for that number. Note that this may be done as part of the previous step.

On the Numbers tab of your Trunk, click Enable next to the number you want to enable for emergency calling. You can also enable emergency calling on the phone number’s configuration page in the Console’s Phone Numbers section.

Change a Twilio phone number’s Emergency Address to a new address

  • Disable Emergency Calling on your Twilio phone number.
  • Check the number’s Emergency Calling Status to verify that it is Inactive.
  • Associate a new Emergency Address with the number.
  • Enable Emergency Calling on the number.
  • Check the number’s Emergency Calling Status to verify that it is Active.

Modify a Twilio phone number’s Emergency Address

  • Disable Emergency Calling on your Twilio number. This must be done on all numbers using this address.
  • Check the number’s Emergency Calling Status to verify that it is Inactive.
  • Dis-associate the Emergency Address from the number.
  • Modify the Emergency Address.
  • Re-associate the Emergency Address with the number.
  • Enable Emergency Calling on the number.
  • Check the number’s Emergency Calling Status to verify that it is Active.

Test Emergency Calling in the US and CA

If you want to check that your communications infrastructure was properly configured for Emergency Calling, you can make a test call by dialling 933. You’ll be connected to an automated system that will read back the Twilio phone number that you’re calling from, along with the address associated with that number.

Note You may need to add 933 to your dial plan in order for the call to be made.

Placing a live emergency call

  • When placing an emergency call, the Request-URI must be formatted as follows: sip:911@{your-trunk}.pstn.twilio.com, or sip:933@{your-trunk}.pstn.twilio.com for a test emergency call.
  • Ensure that your equipment’s dial plan is set up to send outbound 112, 999, 911, and/or 933 calls to Twilio.

You may place a live emergency test call to verify the information that the emergency responder receives. This must be done sparingly. Some localities require you to schedule emergency test calls in advance and will charge penalties otherwise. You should check with your local authorities before placing any unscheduled emergency call tests.

To make a live emergency test call, please follow this script:

  • Hello, this is not an emergency call. This is a test. Do you have a moment to verify my emergency information or can we schedule a later time to do so?
  • Can you verify the address that you received for my call? — confirm that this matches your intended emergency address.
  • Can you verify the telephone number you received for my call? — confirm that this matches the Twilio Number that you called from.
  • Thank you for your time.

If for any reason there is an address mismatch, please file a support ticket.

Important configuration steps

  • Any emergency call must come with a valid From: header. This means it must:
    1. Use an E.164-formatted SIP URI.
    2. Be a Twilio number that is enabled for emergency calling.
      More specifically, all trunk termination traffic must include the following header: From: sip:+1NPANXXYYYY@your-domain.com where 1NPANXXYYYY has to be a Twilio phone number enabled for Emergency Calling and that is associated with the Trunk used for this call.
  • Configure your Elastic SIP Trunk’s Origination settings appropriately so it is able to receive calls from the PSTN into your communications infrastructure. This is important in case your call gets disconnected and the emergency responder needs to call you back. Find out how you can test your Origination settings.
  • When placing an emergency call, the Request-URI must be formatted as follows: sip:911@{your-trunk}.pstn.twilio.com, or sip:933@{your-trunk}.pstn.twilio.com for an emergency test call.
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