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Emergency Calling for SIP Interfaces

Twilio's Emergency Calling enables 911 call routing to Public Safety Answering Points (PSAPs) in the US and Canada. Twilio supports both Enhanced 911 (E911) as well as Basic 911.

E911 calls are routed to the PSAP serving the configured address associated with the phone number from where the call originated. The call automatically includes the end user's Twilio Number and corresponding address information to the 911 dispatcher answering the call.

Basic 911 calls are routed to the designated PSAP serving the customer's configured address from where the call originates. With Basic 911, the 911 dispatcher answering the phone will not have access to the customer's' telephone number or emergency address information unless the customer provides such information verbally during the emergency call.

Certain Twilio 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 Customer’s name, telephone number, and location, and then transfer the Customer to the appropriate local PSAP or otherwise determine the best way to provide emergency services to the Customer.

You can configure Emergency Calling with Programmable Voice SIP Interfaces via the Console as outlined below, or via the API.

We provide you two different granular approaches. The first approach is to configure emergency calling on individual phone numbers, for example if you want each individual agent or user to have their own call back phone number for emergency services, then you make sure to configure their SIP Phone with the appropriate phone numbers. The second approach would be configuring one emergency callback phone number for your SIP Domain, for example if you want to have emergency calling for a building or store using a single number.

Use case 1: To enable Emergency Calling on a Twilio number

  1. Purchase a US or CA Twilio Phone Number
  2. Configure webhook URL on the Phone Number
  3. Validate and associate an address with your Twilio number
  4. Enable Emergency Calling on that number
  5. Configure & Register with SIP Domain
  6. Enable SIP Domain
  7. Test an emergency call
  8. Placing a 911 call

Use case 2: To enable Emergency Calling on a with Emergency Caller ID

  1. Purchase a US or CA Twilio Phone Number
  2. Configure webhook URL on the Phone Number
  3. Validate and associate an address with your Twilio number
  4. Enable Emergency Calling on that number
  5. Enable SIP Domain
  6. Set Emergency CallerID
  7. Register your SIP phone with your SIP Domain
  8. Test an emergency call
  9. Placing a 911 call

Configure Webhook URL on the Phone Number

You will need to configure the Phone Number you would like to use for Emergency Calling with a valid Webhook URL. This cannot be left blank or be the Twilio demo URL. Once you save you will be able to click Enable under the Phone Number Voice Configuration section.

Validate and associate an address with your Twilio number

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, which must be recognized by the Master Street Address Guide (MSAG) database, that will be used for emergency calling, and may be used to dispatch police, fire, emergency medical and other response resources. Please note, the MSAG address will often differ from the USPS postal address because the MSAG uses the community name (township, city, county) where the closest responding PSAP will come from. Each address created may be used for any phone number valid for emergency calling.

Input your address and then click Save & Continue. If there are any issues with your address in the validation process, suggestions will be displayed and you will be asked to select one of the alternatives. This will associate the address with the Twilio Number(s) you selected. If you need any assistance with address validation, please reach out to our support team.

Enable Emergency Calling on that Number

Once you’ve validated an address and associated it with a Twilio Number, you may proceed to enable that Twilio Number for Emergency Calling. Note that this may be done as part of the previous flow when you validate and associate an address with your Twilio Number.

Configure & Register with SIP Domain

Register your Twilio E911 Phone Numbers with your SIP Domain. The SIP phone you are registering with should be configured to send the assigned Twilio E911 number in the From header for the 911 call. Learn more about SIP Registration.

Enable SIP Domain

Once you’ve configured your SIP Domain, you may proceed to enable that Twilio Number for Emergency Calling.

Emergency calls (911) will only be routed when Twilio Numbers enabled for Emergency Calling are used as the Caller-ID (SIP From: header). Emergency call from any other number will be rejected.

Emergency Calling configuration for Programmable Voice SIP Interface is done on the Phone Number configuration page.

Set Emergency Caller ID

Once you have enabled your SIP Domain for Emergency Calling you will have the option of setting an Emergency Caller ID for that SIP Domain if you would like to provide a single phone number as a callback number to emergency services. The Emergency Caller ID will be used to send as the "From" in the SIP header when making a call to emergency services. You will only be able to select a Twilio phone number which has been enabled for emergency calling. Please be sure to select a number from the country you would like to place emergency calls in. This is done from SIP Domain configuration page.

You must then ensure that

  • Any Emergency call (911) must come from a Twilio Number enabled for Emergency Calling (identified in the SIP `From:` header).
  • You configure your Webhook URL appropriately on your Phone Number. This is important in case the emergency responder needs to call you back.

Test an Emergency Call

If you want to practice making a call to check that your communications infrastructure was properly configured for Emergency Calling, you can make a test call by dialling 9-3-3.

By placing a 933 call you'll be connected to an automated system that will read back the Twilio Number that you're calling from, along with the address that is associated with that number.

To call the 933 service, just make the call to 933 instead of 911. You may need to add this to your dial plan in order for the call to be made.

Placing a 911 Call

  • When placing an emergency call, the Request-URI must be formatted as follows: sip:911@<CompanyName>.sip.us1.twilio.com or sip:933@<CompanyName>.sip.us1.twilio.com for an emergency test call.
  • Ensure that the SIP phone is configured to send the assigned Twilio E911 number in the From header for the 911 call
  • Ensure that your equipment/endpoint dial plan is set-up to send outbound 911 and 933 calls to Twilio.

When an emergency call is made Twilio will ignore the Webhook and route directly to the appropriate Public Safety Answering Point (PSAP).

You may place a live 911 test call and verify the information that the emergency responder receives, this should be done sparingly. Note that some localities require you to schedule 911 test calls in advance and will charge penalties otherwise. You should check with your local authorities before placing any unscheduled 911 test calls.

  • 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 your Twilio Number that you called from)
  • Thank you for your time.

Important configuration steps

  • Any 911 call must come with a valid From: header. This means it must use, (1) an E.164 formatted SIP URI, and (2) be a Twilio number that is enabled for emergency calling. More specifically, the SIP phone should be configured to send the assigned Twilio E911 number in the From header for the 911 call and must include the following header: From: sip:+1NPANXXYYYY@<CompanyName>.sip.us1.twilio.com where 1NPANXXYYYY has to be an emergency enabled Twilio number that is associated with the SIP Domain used for this call.
  • Configure appropriately on your Phone Number with a valid Webhook URL to be 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.
  • When placing an emergency call, the Request-URI must be formatted as follows: sip:911@<CompanyName>.sip.us1.twilio.com or sip:933@<CompanyName>.sip.us1.twilio.com for an emergency test call.

Changing the Emergency Address on a Twilio Number to a new Address

  • Disable Emergency Calling on your Twilio Number
  • Check Emergency Calling Status on a Twilio number to ensure it's Inactive
  • Associate new Emergency Address with Twilio Number
  • Enable Emergency Calling on the Twilio Number
  • Check Emergency Calling Status on a Twilio number to ensure it's Active

Modify the existing Emergency Address on a Twilio Number

  • Disable Emergency Calling on your Twilio Number (this must be done on all numbers using this Emergency Address)
  • Check Emergency Calling Status on a Twilio number to ensure it's Inactive
  • Dis-associate the Emergency Address with Twilio Number
  • Modify the Emergency Address
  • Re-associate the Emergency Address with Twilio Number
  • Enable Emergency Calling on the Twilio Number
  • Check Emergency Calling Status on a Twilio number to ensure it's Active

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

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