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Documentation Index

Fetch the complete documentation index at: https://developers.telnyx.com/llms.txt

Use this file to discover all available pages before exploring further.

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UAC SIP Connections

A UAC (User Agent Client) Connection registers Telnyx to your PBX — the opposite of a standard SIP trunk, where the PBX registers to Telnyx. Use UAC when your PBX doesn’t support outbound SIP registration or you need Telnyx to maintain the registration.

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Create a Connection

POST /v2/uac_connections 
curl -X POST https://api.telnyx.com/v2/uac_connections \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "connection_name": "My UAC Connection"
  }'
connection_name is the only required field. You can also provide user_name and password at creation time — if omitted, Telnyx auto-generates them. 
curl -X POST https://api.telnyx.com/v2/uac_connections \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "connection_name": "My UAC Connection",
    "user_name": "my-sip-user",
    "password": "my-sip-password"
  }'

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Connection Fields

Note: fqdn and registration_status are automatically generated by Telnyx. user_name and password are auto-generated if not provided.

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External Settings (external_uac_settings)

These are the SIP credentials Telnyx uses to register to your PBX. The proxy field is required — it’s the SIP server address Telnyx will register to. username and password are the SIP credentials for that registration. transport specifies the transport protocol (TCP, UDP, or TLS). PATCH /v2/uac_connections/ 
curl -X PATCH https://api.telnyx.com/v2/uac_connections/{id} \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "external_uac_settings": {
      "proxy": "sip:pbx.example.com:5060",
      "username": "telnyx-reg",
      "password": "s3cret",
      "transport": "TCP"
    }
  }'

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Internal Settings (internal_uac_settings)

These route inbound calls from the PBX to a Telnyx application. The key field is destination_uri — a SIP URI that tells Telnyx where to send the call.

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destination_uri format

<extension>@<applicationFQDN>.sip.telnyx.com
PartDescription
extensionPBX extension or dial string
applicationFQDNTelnyx application FQDN (e.g. assistant-<uuid> for AI Assistant, cc-app-<id> for Call Control, stt-<id> for Speech-to-Text)
Examples:
destination_uriRoutes to
1006@assistant-abc123.sip.telnyx.comExtension 1006 → AI Assistant (UUID abc123)
2000@cc-app-xyz789.sip.telnyx.comExtension 2000 → Call Control app (ID xyz789)
PATCH /v2/uac_connections/ 
curl -X PATCH https://api.telnyx.com/v2/uac_connections/{id} \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "internal_uac_settings": {
      "destination_uri": "1006@assistant-abc123.sip.telnyx.com"
    }
  }'

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Full Example

Create a UAC connection with all settings in a single request: 
curl -X POST https://api.telnyx.com/v2/uac_connections \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "connection_name": "Office PBX",
    "user_name": "my-sip-user",
    "password": "my-sip-password",
    "external_uac_settings": {
      "proxy": "sip:pbx.example.com:5060",
      "username": "telnyx-reg",
      "password": "s3cret",
      "transport": "TCP"
    },
    "internal_uac_settings": {
      "destination_uri": "1006@assistant-abc123.sip.telnyx.com"
    }
  }'

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Manage Connections

# List all UAC connections
curl https://api.telnyx.com/v2/uac_connections \
  -H "Authorization: Bearer $TELNYX_API_KEY"

# Get a specific connection
curl https://api.telnyx.com/v2/uac_connections/{id} \
  -H "Authorization: Bearer $TELNYX_API_KEY"

# Delete a connection
curl -X DELETE https://api.telnyx.com/v2/uac_connections/{id} \
  -H "Authorization: Bearer $TELNYX_API_KEY"