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

# Overview

> Connect an agent to the phone network and handle real call flows like IVR, transfers, and voicemail.

Telephony connects your AI agent to the phone network over SIP so it can take inbound and place outbound calls. This section covers keypad input, routing, transfers, and voicemail so your agent can handle real phone interactions.

## Inbound and Outbound

Telephony works in both directions, and the features you reach for depend on the call's origin:

* **Inbound:** a caller dials a number routed to your agent through an Inbound SIP gateway. DTMF and IVR routing are most common here, letting callers navigate menus or reach the right department.
* **Outbound:** your agent places the call. Voicemail detection matters most here, since unanswered calls are often forwarded to a voicemail system.

Transfers apply to either direction once a call is connected.

<CardGroup cols={3}>
  <Card title="Routing Rules" icon="route" href="/telephony/call-routing/setting-up-routing-rules">
    Route inbound calls to the right room or agent.
  </Card>

  <Card title="DTMF Events" icon="hashtag" href="/build/telephony/dtmf">
    Capture caller key presses and drive IVR flows on inbound calls.
  </Card>

  <Card title="Voicemail Detection" icon="voicemail" href="/build/telephony/voicemail-detection">
    Detect voicemail systems on outbound calls.
  </Card>
</CardGroup>

## Transfers vs Handoff

Moving a caller can mean two different things, and it's worth keeping them straight:

* **Call Transfer** forwards the SIP call to a new number directly.
* **Agent Handoff** keeps the call in place and switches which agent is responsible for it.

<CardGroup cols={2}>
  <Card title="Call Transfer" icon="phone-arrow-right" href="/build/telephony/call-transfer">
    Move a live call to another number.
  </Card>

  <Card title="Agent Handoff" icon="arrow-right-arrow-left" href="/build/agent-handoffs">
    Switch which agent is responsible for a call without moving it.
  </Card>
</CardGroup>

## References

<Tabs>
  <Tab title="Python">
    #### SDK Reference

    <CardGroup cols={2}>
      <Card title="DTMF Handler" icon="hashtag" href="/api-reference/python/core/tools-and-mcp">
        `DTMF Handler` in the Python API reference.
      </Card>

      <Card title="Voicemail Detector" icon="voicemail" href="/api-reference/python/core/tools-and-mcp">
        `Voicemail Detector` in the Python API reference.
      </Card>
    </CardGroup>
  </Tab>
</Tabs>