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

# Overview: Telephony

> Two ways to put an agent on a phone line.

Voice agents are most useful on an actual phone. There are two routes, and the
right one depends on whether you already run telephony.

<CardGroup cols={2}>
  <Card title="Numbers in Omnia" icon="phone" href="/telephony/phone-numbers">
    Import a number, attach it to an agent, done. Nothing else to build.
  </Card>

  <Card title="Bring your own" icon="tower-cell" href="/telephony/bring-your-own">
    Keep your carrier. Stream audio to a WebSocket we return.
  </Card>
</CardGroup>

## Which one

|              | Numbers in Omnia          | Bring your own                                             |
| ------------ | ------------------------- | ---------------------------------------------------------- |
| You manage   | Nothing                   | Carrier, webhooks, call control                            |
| Setup        | One API call              | A webhook handler                                          |
| Call control | Ours                      | Yours                                                      |
| Right when   | You want it working today | You already run telephony, or need control we don't expose |

Most people should start with numbers in Omnia and move later if they need to.
The agent itself is identical either way — the same prompt, tools, and corpora.

## What changes on a phone call

Worth knowing before you point a number at an agent that tested well in a
browser.

**Audio is narrowband.** Phone calls carry G.711 at 8 kHz. A voice that sounds
rich in the browser can sound thin. Always listen to a real call before going
live.

**Client tools do not work.** There is no client on a phone call. An agent that
answers a number needs HTTP or [built-in](/tools/built-in) tools — a client tool
silently never fires.

**`hangUp` becomes essential.** Without it the agent finishes speaking and waits,
and the caller sits in silence. In a browser they can close the tab; on a phone
they cannot.

**Callers interrupt, and there is background noise.** Cars, offices, other
people. Set `interruptible` deliberately and test somewhere noisy.

## Outbound

Both routes support outbound calls. The agent always waits for the callee to
speak first, whatever the agent's `firstSpeaker` says — they answered the phone,
so they say hello.

```bash theme={null}
POST /calls/outbound
{ "agentId": "…", "phoneNumber": "+358401234567", "fromNumberId": "…" }
```

<Warning>
  Automated outbound calling is regulated, and the rules differ sharply by
  country — consent, permitted hours, identification, do-not-call registers.
  Check what applies where you are dialling. This is your obligation.
</Warning>

## Transfers

An agent can hand a call to a human. See [Call transfers](/telephony/transfers).