# Telnyx Calling: UAC Connections — Documentation Index
> UAC Connections documentation within the Calling section of the Telnyx developer docs (https://developers.telnyx.com).
> Root index: https://developers.telnyx.com/llms.txt · Calling index: https://telnyx-openapi-ng.s3.us-east-1.amazonaws.com/llms/calling.txt · Full content for this subsection: https://telnyx-openapi-ng.s3.us-east-1.amazonaws.com/llms/calling/uac-connections-full.txt

- [UAC Connections](https://developers.telnyx.com/docs/voice/uac-connections.md): SIP Attach connects your existing PBX or SIP platform to Telnyx. Create a UAC Connection so Telnyx registers to your PBX and routes calls to Telnyx applications.

## API Reference (UAC Connections)

### UAC Connections

- [List UAC connections](https://developers.telnyx.com/api-reference/uac-connections/list-uac-connections.md): Returns a list of your UAC connections. A UAC (User Agent Client) Connection registers Telnyx to your PBX — the opposite of a standard SIP trunk, where the PBX…
- [Create a UAC connection](https://developers.telnyx.com/api-reference/uac-connections/create-a-uac-connection.md): Creates a UAC connection. A UAC (User Agent Client) Connection registers Telnyx to your PBX — the opposite of a standard SIP trunk, where the PBX registers to…
- [Retrieve a UAC connection](https://developers.telnyx.com/api-reference/uac-connections/retrieve-a-uac-connection.md): Retrieves the details of an existing UAC connection.
- [Update a UAC connection](https://developers.telnyx.com/api-reference/uac-connections/update-a-uac-connection.md): Updates settings of an existing UAC connection.
- [Delete a UAC connection](https://developers.telnyx.com/api-reference/uac-connections/delete-a-uac-connection.md): Deletes an existing UAC connection.
- [Check a UAC Connection Registration Status](https://developers.telnyx.com/api-reference/uac-connections/check-a-uac-connection-registration-status.md): Checks the registration status for a UAC connection (`registration_status`) as well as the timestamp for the last SIP registration event (`registration_status_…
- [SIP Registration Status](https://developers.telnyx.com/api-reference/uac-connections/sip-registration-status.md): Returns the live SIP registration state of a UAC connection: whether it is currently registered, when it last registered, and the last response Telnyx received…