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TurnCall has no SIP endpoint of its own: it does not accept SIP or RTP. A phone system with an elastic SIP trunk on Twilio or Telnyx reaches an agent by dialling a number TurnCall already routes. The carrier takes the SIP call off your trunk and delivers it to that number like any other call, and TurnCall answers it over the carrier’s media stream.
This works from any system that can send a call over the trunk: a PBX, a contact-centre platform, an SBC. If you run Asterisk and want no cloud carrier in the call, see SIP trunk through Asterisk.

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TurnCall side

Bind a Twilio or Telnyx number to the agent, exactly as in Phone Numbers. On Twilio:
On Telnyx, add "carrier": "telnyx" (external_number_sid is then optional). Binding points the number at TurnCall when PUBLIC_BASE_URL is set; webhooks_configured in the response says whether it did. The number must route to TurnCall, not to your trunk:
  • Twilio: a number associated with an Elastic SIP Trunk ignores its voice URL; Twilio sends its calls to the trunk. Binding sets the voice URL but does not take the number off a trunk. Use a number that is on no trunk, or remove it from the trunk (the trunk’s Numbers list in the Twilio Console) before you bind it.
  • Telnyx: a number belongs to one connection. Binding moves it onto TurnCall’s Call Control application, so it stops ringing on your SIP Connection. Use a number your phone system does not answer itself.

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Carrier side

Your trunk needs to carry calls out of your phone system (termination). If it already dials the public network, there is nothing to change.

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Twilio

In the Twilio Console, under Elastic SIP Trunking > Trunks, create a trunk and set up Termination:
  • Termination SIP URI: the address your phone system sends calls to, <name>.pstn.twilio.com.
  • Authentication: a Credential List (digest username and password), an IP Access Control List of your phone system’s addresses, or both. Twilio recommends credentials: an IP list alone does not protect against some attacks.
Twilio’s requirements for each call your phone system sends:
  • The dialled number in E.164, with the +: +15551234567.
  • A caller ID that is one of your Twilio numbers or a verified caller ID on the account.
See Twilio’s Elastic SIP Trunking docs for the full setup.

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Telnyx

In Mission Control, create a SIP Connection:
  • Authentication: credentials (your phone system authenticates to sip.telnyx.com with the connection’s username and password), or your phone system’s IP addresses or FQDN.
  • An Outbound Voice Profile assigned to the connection. Telnyx requires one for outbound calls.
Dial the number in E.164, with the +, as Telnyx’s own PBX guides do. See Telnyx’s SIP trunking docs for the full setup.

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Phone system side

Route a call to the agent by dialling the bound number over the trunk: an outbound route, a speed dial, a queue overflow, or a transfer of a live call. In an Asterisk dialplan, with the trunk endpoint named twilio:

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What the agent sees

  • to_number is the bound number.
  • from_number is the caller ID your phone system sent on the trunk. On Twilio that is one of your numbers or a verified caller ID, so a caller your phone system forwards arrives with that caller ID, not their own.
Everything else is as on any Twilio or Telnyx number: routing to an agent or a Call Init webhook, recording, transfers, DTMF, and outbound calls from the number. A transfer dials a phone number through the carrier; to send a caller back into your phone system, transfer to a number that rings there.