> ## Documentation Index
> Fetch the complete documentation index at: https://docs.open.cx/llms.txt
> Use this file to discover all available pages before exploring further.

# Phone overview

> Overview of the AI phone channel — voice agents answer calls, make outbound calls, transfer to humans, and integrate with your carrier via SIP.

Customers call your number. An AI voice agent answers, handles the conversation, and can transfer to a human when needed. Your team sees full transcripts in the [inbox](https://platform.open.cx/inbox).

<Tip>
  New here? Skim this page, then open **[Create Phone Agent](/phone/create-agent)** to go live.
</Tip>

## Core Functionality

<AccordionGroup>
  <Accordion title="Inbound Calls" icon="phone-arrow-down-left">
    Customers call your number and the AI voice agent answers. Calls are routed to the correct agent based on the phone number dialed. See [Inbound Calls](/phone/inbound-calls).
  </Accordion>

  <Accordion title="Outbound Calls" icon="phone-arrow-up-right">
    Initiate AI-powered outbound calls from the dashboard, via API, or through workflows. See [Outbound Calls](/phone/outbound-calls).
  </Accordion>

  <Accordion title="Voice Agent" icon="robot">
    Configure voice, language, speaking speed, and background noise. Write instructions as free text or build a visual call flow. See [Agent Configuration](/phone/agent-config).
  </Accordion>

  <Accordion title="Call Transfers" icon="arrow-right-arrow-left">
    <Tooltip tip="The AI hands the live call to a human agent, external phone number, or SIP destination mid-conversation.">Transfer calls</Tooltip> to human agents, external phone numbers, or SIP destinations. Define transfer targets at the org level and assign them per agent.
  </Accordion>

  <Accordion title="Knowledge Sources" icon="book">
    Connect your published knowledge base to the agent. The AI references it during calls to answer customer questions accurately.
  </Accordion>

  <Accordion title="Actions And Workflows" icon="bolt">
    The AI can trigger tools and workflows during a call — look up orders, create tickets, update records. See [AI Actions](/actions/introduction).
  </Accordion>

  <Accordion title="Zendesk" icon="headset">
    Forward Zendesk Talk calls into your OpenCX phone agent, and transfer calls from OpenCX back into the Zendesk Agent Workspace over SIP-IN. Transcripts and handoff context sync to the ticket. See [Zendesk Telephony](/integrations/zendesk/telephony).
  </Accordion>

  <Accordion title="SIP / BYOC" icon="server">
    <Tooltip tip="Bring Your Own Carrier — use your existing telephony provider instead of OpenCX-hosted numbers." cta="SIP setup" href="/phone/sip-integration">Bring your own carrier</Tooltip> via SIP trunking. Route inbound and outbound calls through your existing telephony provider.
  </Accordion>

  <Accordion title="Transcripts And Recording" icon="microphone">
    Calls are transcribed in real time. Full transcripts appear in the [inbox](https://platform.open.cx/inbox) alongside chat and email conversations.
  </Accordion>
</AccordionGroup>

<Note>
  Phone numbers must be verified under **[Settings → Phone Numbers](https://platform.open.cx/settings/phone-numbers)** before they can be assigned to agents. You can also [contact us](mailto:support@open.cx) to manually add verified numbers.
</Note>

## Integration Options

Phone agents integrate with your own carrier over SIP, and with Zendesk for ticketing and human handoff.

<Tabs>
  <Tab title="SIP / Bring your own carrier">
    Route inbound and outbound calls through your existing telephony provider instead of OpenCX-hosted numbers. Configure inbound and outbound trunks and transfer destinations from **[Settings → SIP](https://platform.open.cx/settings/sip)**.

    <Card title="SIP Integration" icon="server" href="/phone/sip-integration">
      What OpenCX supports and what your carrier needs to provide.
    </Card>
  </Tab>

  <Tab title="Zendesk">
    Phone agents integrate with Zendesk Talk in both directions:

    * **Inbound** — forward your Zendesk Talk number to a verified OpenCX number. The AI answers first, and an auto-provisioned `ticket.created` webhook links the new phone-channel ticket back to the OpenCX session, enriching the contact with the ticket requester's name, email, and phone.
    * **Outbound transfer** — when the AI hands off, the call rides over Zendesk SIP-IN and lands natively in the Agent Workspace, carrying the originating ticket id so the leg re-associates with the existing voice ticket instead of spawning a duplicate.

    Connect Zendesk under **Integrations → Zendesk** in the dashboard, then add your Zendesk SIP-IN URI as a **SIP** transfer destination on the agent.

    <CardGroup cols={2}>
      <Card title="Zendesk Telephony" icon="phone-arrow-up-right" href="/integrations/zendesk/telephony">
        Inbound forwarding and SIP-IN transfer setup, end to end.
      </Card>

      <Card title="Zendesk Overview" icon="headset" href="/integrations/zendesk/overview">
        Connect Zendesk and configure ticketing.
      </Card>
    </CardGroup>
  </Tab>
</Tabs>

***

## Related Documentation

<CardGroup cols={2}>
  <Card title="Create Phone Agent" icon="plus" href="/phone/create-agent">
    Set up your first voice agent and make a test call.
  </Card>

  <Card title="Agent Configuration" icon="sliders" href="/phone/agent-config">
    Voice, instructions, flow builder, knowledge, and transfers.
  </Card>

  <Card title="SIP Integration" icon="server" href="/phone/sip-integration">
    Bring your own carrier with inbound and outbound SIP trunks.
  </Card>
</CardGroup>