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

# Voice

> Programmable voice calls, SIP trunking, and AI-powered voice agents

# Voice

Build programmable voice experiences with Orbit's voice infrastructure powered by LiveKit. Make and receive calls, connect SIP trunks, deploy AI voice agents with real-time speech-to-text and text-to-speech, and record calls — all through a unified API.

## Make an Outbound Call

```bash theme={null}
curl -X POST https://orbit-api.devotel.io/api/v1/voice/calls \
  -H "X-API-Key: dv_live_sk_..." \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+14155552671",
    "from": "+18005551234",
    "webhook_url": "https://yourapp.com/webhooks/voice",
    "tts": {
      "text": "Hello! This is a call from Orbit.",
      "voice": "alloy"
    }
  }'
```

## Connect to an AI Voice Agent

Route incoming calls to an AI agent for automated conversations:

```bash theme={null}
curl -X POST https://orbit-api.devotel.io/api/v1/voice/calls \
  -H "X-API-Key: dv_live_sk_..." \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+14155552671",
    "from": "+18005551234",
    "agent_id": "agent_support_bot",
    "agent_config": {
      "greeting": "Hi, thanks for calling Acme support. How can I help?",
      "language": "en-US"
    }
  }'
```

## Features

* **Outbound calls** — initiate calls programmatically to any phone number
* **Inbound routing** — route incoming calls to webhooks, agents, or SIP endpoints
* **SIP trunking** — connect your existing PBX infrastructure via SIP
* **AI voice agents** — deploy conversational AI agents powered by LangGraph
* **Speech-to-text** — real-time transcription via Deepgram Nova-3
* **Text-to-speech** — natural voice synthesis via Cartesia Sonic Turbo (40ms TTFA)
* **Call recording** — automatic or on-demand recording with secure storage
* **DTMF input** — collect keypad input for IVR menus
* **Call transfer** — warm and cold transfers to other numbers or agents
* **Conferencing** — multi-party calls with up to 50 participants

## TTS Providers

| Provider   | Model       | Latency      | Best For                           |
| ---------- | ----------- | ------------ | ---------------------------------- |
| Cartesia   | Sonic Turbo | \~40ms TTFA  | Real-time voice agents             |
| ElevenLabs | Flash v2.5  | \~120ms TTFA | Multi-language, content generation |

## Call Status Flow

`initiated` → `ringing` → `in_progress` → `completed` (or `failed` / `busy` / `no_answer`)

## Webhook Events

Orbit sends real-time events during call lifecycle:

| Event                  | Description                         |
| ---------------------- | ----------------------------------- |
| `call.initiated`       | Call has been placed                |
| `call.ringing`         | Destination is ringing              |
| `call.answered`        | Call was answered                   |
| `call.completed`       | Call ended normally                 |
| `call.failed`          | Call failed to connect              |
| `call.recording_ready` | Recording is available for download |