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

# Carrier

> Telephony providers: Twilio and Telnyx.

# Carrier

The carrier delivers the phone call to Patter. Patter supports **Twilio** and **Telnyx**. Both share DTMF, call transfer, AMD, status callbacks, and cost tracking; recording is Twilio-only.

You configure one carrier per `Patter` instance by passing an instance to the `carrier=` keyword argument. Each carrier class falls back to environment variables when constructor arguments are omitted.

Each carrier ships as both a **flat alias** (`from getpatter import Twilio`) and a **namespaced** class (`from getpatter.carriers import twilio` → `twilio.Carrier()`). They are equivalent.

## Twilio

```python theme={null}
from getpatter import Patter, Twilio

phone = Patter(carrier=Twilio(), phone_number="+15550001234")   # reads env
# Or explicitly:
phone = Patter(
    carrier=Twilio(account_sid="AC...", auth_token="..."),
    phone_number="+15550001234",
)
```

| Parameter     | Type  | Default | Description                                                                        |
| ------------- | ----- | ------- | ---------------------------------------------------------------------------------- |
| `account_sid` | `str` | `""`    | Twilio Account SID (starts with `AC`). Reads from `TWILIO_ACCOUNT_SID` when empty. |
| `auth_token`  | `str` | `""`    | Twilio Auth Token. Reads from `TWILIO_AUTH_TOKEN` when empty.                      |

Namespaced form:

```python theme={null}
from getpatter.carriers import twilio

carrier = twilio.Carrier()                            # reads env
carrier = twilio.Carrier(account_sid="AC...", auth_token="...")
```

On `serve()`, Patter automatically sets the `voice_url` on the Twilio number to `https://<webhook_url>/webhooks/twilio/voice` via the Twilio REST API — no manual Console configuration needed.

### Twilio trial account limitations

Twilio trial accounts apply a few platform-level restrictions that affect first-time testing. None of these are Patter limitations — they're Twilio platform rules:

1. **Verified Caller IDs required for outbound** — trial accounts can only call numbers you've added under **Phone Numbers › Verified Caller IDs** in the Twilio Console. Verifying via the CLI is also restricted; do it from the Console.
2. **Trial announcement prepended on outbound calls** — Twilio plays an English trial-account message before connecting the call to your agent; the callee has to press a key to continue.
3. **Trial caller-ID restrictions** — the caller-ID shown to the recipient may be masked or labelled differently than your purchased number until the account is upgraded.

Upgrading the account in the Twilio Console clears all three. Refer to the Twilio docs (search: "trial account") for the current exact behaviour — Twilio may change these over time.

### Signature verification

The Auth Token is also used to verify every Twilio webhook with HMAC-SHA1 against the `X-Twilio-Signature` header. Requests with invalid signatures are rejected with HTTP 403.

## Telnyx

```python theme={null}
from getpatter import Patter, Telnyx

phone = Patter(carrier=Telnyx(), phone_number="+15550001234")    # reads env
# Or explicitly:
phone = Patter(
    carrier=Telnyx(
        api_key="KEY...",
        connection_id="2000000000000000000",
        public_key="...",  # optional — enables Ed25519 signature verification
    ),
    phone_number="+15550001234",
)
```

| Parameter       | Type  | Default | Description                                                                                                 |
| --------------- | ----- | ------- | ----------------------------------------------------------------------------------------------------------- |
| `api_key`       | `str` | `""`    | Telnyx API v2 key. Reads from `TELNYX_API_KEY` when empty.                                                  |
| `connection_id` | `str` | `""`    | Call Control Application ID. Reads from `TELNYX_CONNECTION_ID` when empty.                                  |
| `public_key`    | `str` | `""`    | Optional. Ed25519 public key for webhook signature verification. Reads from `TELNYX_PUBLIC_KEY` when empty. |

Namespaced form:

```python theme={null}
from getpatter.carriers import telnyx

carrier = telnyx.Carrier()                            # reads env
```

### Signature verification

When `public_key` is set (or `TELNYX_PUBLIC_KEY` is present), every Telnyx webhook is verified with Ed25519. Requests older than 5 minutes are rejected (replay protection).

## Webhook Endpoints

The embedded server exposes these endpoints regardless of carrier choice:

| Endpoint                          | Purpose                                                                    |
| --------------------------------- | -------------------------------------------------------------------------- |
| `POST /webhooks/twilio/voice`     | Incoming Twilio call → returns TwiML to start streaming.                   |
| `POST /webhooks/twilio/status`    | Call lifecycle status callbacks (initiated, ringing, answered, completed). |
| `POST /webhooks/twilio/recording` | Recording completion callbacks.                                            |
| `POST /webhooks/twilio/amd`       | Async AMD (answering machine detection) results.                           |
| `POST /webhooks/telnyx/voice`     | Incoming Telnyx call → returns Call Control commands.                      |

## Outbound calls

Use `phone.call(...)` to place an outbound call on either carrier. Every keyword argument is **snake\_case**:

```python theme={null}
import asyncio
from getpatter import Patter, Twilio, OpenAIRealtime

phone = Patter(carrier=Twilio(), phone_number="+15550001234")
agent = phone.agent(engine=OpenAIRealtime(), system_prompt="You are a friendly receptionist.")

async def main():
    server = asyncio.create_task(phone.serve(agent, tunnel=True))
    await phone.ready                                   # wait until tunnel + listener are up

    await phone.call(
        to="+15550009876",
        agent=agent,
        first_message="Hi! This is a courtesy call from Acme.",
        machine_detection=True,                          # default since 0.6.2
        ring_timeout=25,                                 # default since 0.6.2
        voicemail_message="Please call us back at +15550001234.",
    )

asyncio.run(main())
```

Key defaults changed in 0.6.2:

* `machine_detection` defaults to `True`. On Twilio Patter sends `MachineDetection=DetectMessageEnd` + Async AMD so there is no answer-latency penalty on human pickups. Pass `False` to skip per-call AMD billing.
* `ring_timeout` defaults to `25` seconds. Pass `60` for legacy carrier-default parity, or `None` to omit the parameter entirely.
* The AMD callback was renamed `on_machine` → `on_machine_detection` and now receives a `MachineDetectionResult` (not a raw dict).

See [Local Mode › call() Parameters](/python-sdk/local-mode#call-parameters-local-mode) for the full parameter table.

## What's Next

<CardGroup cols={2}>
  <Card title="STT" icon="microphone" href="/python-sdk/stt">Speech-to-text providers.</Card>
  <Card title="LLM" icon="brain" href="/python-sdk/llm">Language model providers.</Card>
  <Card title="TTS" icon="volume" href="/python-sdk/tts">Text-to-speech providers.</Card>
  <Card title="Tunneling" icon="cloud" href="/dev-tools/tunneling">Expose your local server publicly.</Card>
</CardGroup>