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

# Connection Modes

> The three ways to connect your phone system to SmartAlex: standard SIP trunk, native extension mode, or DID forwarding. Pick the one that fits your setup.

There are three ways to point your phone system at SmartAlex. All of them land the caller on the same voice engine, so the AI behaves identically once the call arrives. The only difference is who initiates the connection and who owns the routing. Pick the mode that matches how your telephony is set up today.

<Note>
  You do not have to choose one mode for your whole account. Modes coexist on the same SmartAlex tenant, so you can run a standard trunk for one number, a native extension for another, and forward a third. Start with whichever is easiest to stand up, then add others as you grow.
</Note>

## How the three modes connect

```mermaid theme={null}
flowchart LR
  subgraph Trunk["Standard SIP trunk (default)"]
    T1["Your PBX or carrier"]
    T2["SIP trunk points at our ingress"]
    T1 --> T2
  end

  subgraph Extension["Native extension mode"]
    E1["Your PBX"]
    E2["We register as an extension on it"]
    E1 --> E2
  end

  subgraph Forwarding["DID forwarding"]
    F1["Your carrier number"]
    F2["Forward the DID to us"]
    F1 --> F2
  end

  Engine["The voice engine answers the caller"]
  T2 --> Engine
  E2 --> Engine
  F2 --> Engine
```

The direction of the arrow is the thing that changes. With a standard trunk, your system sends calls out to us. With native extension mode, we register into your PBX and it treats us like a desk phone. With DID forwarding, your carrier redirects a number to us at the network level.

## Comparison

| Mode                  | How it connects                                                                                                                                                                 | Best for                                                                                                                               |
| --------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |
| Standard SIP trunk    | Your PBX or carrier sends calls out to our SIP ingress over a trunk you configure. This is the default and the most direct path.                                                | Teams that run a SIP-capable PBX and want a clean, dedicated route to the AI with the least moving parts.                              |
| Native extension mode | We register as an extension on your PBX, just like a handset. Anyone in the office can dial that extension, and the AI appears in your directory, ring groups, and hunt groups. | Businesses that want the AI to live inside the existing PBX, be reachable from desk phones, and follow native transfer and ring rules. |
| DID forwarding        | You forward a phone number from your carrier to a number or address we give you. No trunk, no registration, no PBX changes.                                                     | The fastest start, or anyone without a PBX. Also good when you only want to redirect a single number to the AI.                        |

## How to choose

<AccordionGroup>
  <Accordion title="I have a SIP-capable PBX and want a clean setup">
    Use the standard SIP trunk. It gives the AI a dedicated route, keeps your PBX as the source of truth for transfers, and is the least likely to interact with your existing dial plan. This is the default for a reason.
  </Accordion>

  <Accordion title="I want the AI to be one of the phones on my PBX">
    Use native extension mode. The AI registers into your PBX and can be dialled internally, added to ring groups, and included in follow-me rules. You provision the credentials on the PBX side, so your team keeps full control of routing.
  </Accordion>

  <Accordion title="I want the fastest possible start, or I do not run a PBX">
    Use DID forwarding. You point a number at us and you are live in minutes. There is nothing to install and no PBX configuration to touch, which makes it the quickest way to pilot the AI on a single number.
  </Accordion>

  <Accordion title="Can I mix modes?">
    Yes. Every mode is per number and per agent, so a single account can run all three at once. A common pattern is to forward one number for a quick pilot, then move to a standard trunk or native extension once you are ready to route production traffic.
  </Accordion>
</AccordionGroup>

## Pick your mode

<CardGroup cols={3}>
  <Card title="Standard SIP trunk" href="/telephony/standard-trunk">
    The default. Your PBX or carrier sends calls to our SIP ingress over a trunk you configure.
  </Card>

  <Card title="Native extension mode" href="/telephony/native-extension-mode">
    We register as an extension on your PBX. Dial it from any desk phone and the AI answers.
  </Card>

  <Card title="DID forwarding" href="/telephony/did-forwarding">
    Forward a number to us at the carrier level. No trunk, no registration, no PBX changes.
  </Card>
</CardGroup>