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SIP trunk

Telnyx AI voice agents on an FQDN SIP connection

Route inbound Telnyx calls to sip.cartesia.ai, link the trunk and assign an agent, and you keep your numbers and per-minute rates.

Start buildingRead the docs
create-provider.sh
curl -X POST "https://api.cartesia.ai/agents/phone-numbers/providers" \
  -H "X-API-Key: $CARTESIA_API_KEY" \
  -H "Cartesia-Version: 2026-08-14" \
  -H "Content-Type: application/json" \
  -d '{
    "type": "sip_trunk",
    "label": "Telnyx",
    "inbound": {
      "allowed_addresses": ["TELNYX_SIGNALING_IP_RANGE"],
      "media_encryption": "allowed"
    },
    "outbound": {
      "address": "sip.telnyx.com",
      "transport": "tcp",
      "destination_country": "US",
      "credentials": { "username": "YOUR_TELNYX_USERNAME", "password": "YOUR_TELNYX_PASSWORD" }
    }
  }'

Cartesia docs: SIP trunking

What a Telnyx AI voice agent can do

What teams build when they put Cartesia and Telnyx together.

Your numbers and rates

Cartesia charges only agent calling rates on a SIP trunk number, and Telnyx bills its own rates for the line.

Two-way calling

Inbound calls reach the agent assigned to the dialed number, and outbound calls go through Telnyx's SIP endpoint.

Transfers

The agent transfers calls by SIP REFER to a phone number or a SIP URI, as long as Telnyx accepts the REFER.

Telnyx settings

Connection type
FQDN
FQDN
sip.cartesia.ai
Destination number format
+E.164
Transport
TCP
Outbound address in Cartesia
sip.telnyx.com
Outbound credentials
The username and password from the connection's Outbound Calls Authentication.

Set it up

A SIP trunk: an FQDN connection at Telnyx that points at sip.cartesia.ai, linked to Cartesia as a provider. There is no native Telnyx integration. Vendor details read in October 2026.

  1. Create an FQDN connection at Telnyx

    In the Telnyx portal, create a SIP connection of type FQDN and add sip.cartesia.ai as its FQDN.

  2. Set the inbound format and transport

    Set the destination number format to +E.164 and choose TCP, so calls arrive at sip:sip.cartesia.ai;transport=tcp.

  3. Add outbound credentials and a voice profile

    Under Outbound Calls Authentication, set a username and password. Attach an outbound voice profile so the connection can place calls.

  4. Assign numbers, then link the trunk in Cartesia

    Assign your Telnyx numbers to the connection. In Cartesia, create a provider with sip.telnyx.com as the outbound address and the same username and password, then import each number and assign an agent.

Documentation

Before you build

Test a transfer early

Transfers go out as SIP REFER. Place a test transfer before launch to confirm the connection accepts it for your destination type.

Format and transport

Set the connection's destination number format to +E.164 and choose TCP, so calls arrive at sip:sip.cartesia.ai;transport=tcp.

Use cases for teams on Telnyx

Customer support

Resolve support calls on the first try, refund and credit within your rules, and keep customers who call to cancel.

See the use case

Appointment scheduling

Book, reschedule and confirm appointments on your calendar, 24/7.

See the use case

More integrations

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Plivo

Run a Cartesia voice agent on Plivo numbers with a Zentrunk SIP trunk, at your Plivo rates.

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Vonage

Run a Cartesia voice agent on Vonage numbers with Vonage SIP Trunking, at your Vonage rates.

  • Managed Agents
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SIP trunk

SIP trunking

Point your carrier at sip.cartesia.ai and run Cartesia voice agents on your own numbers, with TLS, SRTP and digest or IP access control.

  • Managed Agents
See the integration

Enterprise-grade security

  • HIPAA compliant badge

    HIPAA compliant

  • SOC 2 Type 2 badge

    SOC 2 Type 2

  • GDPR badge

    GDPR

Telnyx AI voice agent FAQs

How do I connect Telnyx to an AI voice agent?

Create an FQDN connection in the Telnyx portal that points at sip.cartesia.ai, with the destination number format set to +E.164 and TCP as the transport. Then link the trunk in Cartesia with sip.telnyx.com as the outbound address, import each number and assign an agent. The SIP trunking page covers every Cartesia-side setting.

Does Telnyx have its own AI voice agent?

Yes. Telnyx sells AI Assistants, which run on Telnyx's own platform. Connecting Telnyx to Cartesia over a SIP trunk is the other route, where your numbers and per-minute rates stay at Telnyx and the agent runs on Cartesia.

Can the agent make outbound calls through Telnyx?

Yes. Set a username and password under the connection's outbound calls authentication, attach an outbound voice profile, and enter the same credentials in Cartesia. Cartesia then places calls through sip.telnyx.com with the imported number as the from number.

Can the agent transfer Telnyx calls to a person?

Yes, as a cold transfer by SIP REFER to a phone number or a SIP URI, as long as Telnyx accepts the REFER for that destination. Place a test transfer before launch. If the carrier rejects it, Cartesia keeps the caller connected.

What does a Telnyx number cost on Cartesia?

Telnyx bills the line at your Telnyx rates, and Cartesia adds no telephony fee on a trunk number. Agents run at $0.03/min, plus LLM usage. Numbers that Cartesia provisions, which are US only, carry a $0.014 per minute telephony fee instead.

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