---
name: build-ivr-phone-menu
title: "Build IVR Phone Menu"
description: "Build an interactive voice response menu with DTMF input."
language: python
framework: flask
telnyx_products: [Voice]
---

# Production-ready IVR system using Telnyx Voice API and Flask.

Production-ready IVR system using Telnyx Voice API and Flask.

## Telnyx API Endpoints Used

- **Call Control: Answer**: `POST /v2/calls/{id}/actions/answer` — [API reference](https://developers.telnyx.com/api/call-control/answer-call)
- **Call Control: Speak (TTS)**: `POST /v2/calls/{id}/actions/speak` — [API reference](https://developers.telnyx.com/api/call-control/speak)
- **Call Control: Gather (STT/DTMF)**: `POST /v2/calls/{id}/actions/gather_using_speak` — [API reference](https://developers.telnyx.com/api/call-control/gather)

## Telnyx Webhook Events

This app handles these webhook events ([Call Control docs](https://developers.telnyx.com/docs/api/v2/call-control)):

- `call.dtmf.received` — DTMF tone detected during call
- `call.hangup` — Call ended — app cleans up session, triggers post-call processing
- `call.initiated` — New inbound or outbound call detected
- `call.speak.ended` — TTS playback finished — app transitions to next action (gather, transfer, etc.)

## Architecture

```
  Inbound Phone Call
        │
        ▼
  ┌──────────────────┐
  │ Call Control      │
  └────────┬─────────┘
           │
           ├──► TTS
           ├──► DTMF
           │
           ▼
     JSON response
```

## Environment Variables

Copy `.env.example` to `.env` and fill in:

| Variable | Type | Example | Required | Description | Where to get it |
|----------|------|---------|----------|-------------|-----------------|
| `TELNYX_API_KEY` | `string` | `KEY0123456789ABCDEF` | **yes** | Telnyx API v2 key | [Portal](https://portal.telnyx.com/api-keys) |
| `FLASK_DEBUG` | `string` | `false` | no | Flask debug | — |

## Setup

```bash
git clone https://github.com/team-telnyx/telnyx-code-examples.git
cd telnyx-code-examples/build-ivr-phone-menu-python
cp .env.example .env    # ← fill in your credentials
pip install -r requirements.txt
python app.py           # starts on http://localhost:5000
```

### Webhook Configuration

1. Expose your local server:

   ```bash
   ngrok http 5000
   ```

2. Copy the HTTPS URL and configure in [Telnyx Portal](https://portal.telnyx.com):

   - **Call Control Application** → Webhook URL → `https://<id>.ngrok.io/webhooks/voice`

## Webhook Endpoints

### `POST /webhooks/call`

Receives [Telnyx Call Control](https://developers.telnyx.com/docs/voice/call-control) webhook events.

**Events handled:** `call.dtmf.received`, `call.hangup`, `call.initiated`, `call.speak.ended`

**Example payload:**

```json
{
  "data": {
    "event_type": "call.initiated",
    "id": "0ccc7b54-4df3-4bca-a65a-3da1ecc777f0",
    "occurred_at": "2026-07-15T14:30:00.000Z",
    "payload": {
      "call_control_id": "v3:uMi2qMWHT-mLFGkEm4t9tA",
      "connection_id": "1494404757140276705",
      "call_leg_id": "428c31b6-7af4-4bcb-b7f5-5013ef9657c1",
      "call_session_id": "428c31b6-abcd-1234-5678-5013ef9657c1",
      "client_state": null,
      "from": "+12125551234",
      "to": "+13105559876",
      "direction": "incoming",
      "state": "ringing"
    },
    "record_type": "event"
  },
  "meta": {
    "attempt": 1,
    "delivered_to": "https://your-server.example.com/webhooks/voice"
  }
}
```

### `GET /webhooks/call/status`

Receives [Telnyx Call Control](https://developers.telnyx.com/docs/voice/call-control) webhook events.

**Events handled:** `call.dtmf.received`, `call.hangup`, `call.initiated`, `call.speak.ended`

**Example payload:**

```json
{
  "data": {
    "event_type": "call.initiated",
    "id": "0ccc7b54-4df3-4bca-a65a-3da1ecc777f0",
    "occurred_at": "2026-07-15T14:30:00.000Z",
    "payload": {
      "call_control_id": "v3:uMi2qMWHT-mLFGkEm4t9tA",
      "connection_id": "1494404757140276705",
      "call_leg_id": "428c31b6-7af4-4bcb-b7f5-5013ef9657c1",
      "call_session_id": "428c31b6-abcd-1234-5678-5013ef9657c1",
      "client_state": null,
      "from": "+12125551234",
      "to": "+13105559876",
      "direction": "incoming",
      "state": "ringing"
    },
    "record_type": "event"
  },
  "meta": {
    "attempt": 1,
    "delivered_to": "https://your-server.example.com/webhooks/voice"
  }
}
```

## Testing

```bash
curl http://localhost:5000/health

```json
{"status": "ok"}
```
```

```bash
curl -X POST http://localhost:5000/webhooks/voice \
  -H "Content-Type: application/json" \
  -d '{"data": {"event_type": "call.initiated", "payload": {"call_control_id": "test"}}}''''''''' 
```

## Troubleshooting

| Issue | Cause | Fix |
|-------|-------|-----|
| `401 Unauthorized` | Invalid or missing API key | Verify `TELNYX_API_KEY` in `.env` matches your key in the [Portal](https://portal.telnyx.com/api-keys) |
| Webhook not received | Local server not publicly reachable | Expose it with a tunnel (e.g. ngrok) and set the webhook URL in the [Telnyx Portal](https://portal.telnyx.com) |
| `422 Unprocessable Entity` | Missing or malformed request fields | Check the request body against the API Reference above |

## Related Examples

- [Branded Caller Id Manager (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/branded-caller-id-manager-python/README.md)
- [Build Conference Calling (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/build-conference-calling-python/README.md)
- [Bulk Number Validation Cleaner (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/bulk-number-validation-cleaner-python/README.md)
- [Call Analytics Dashboard Api (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/call-analytics-dashboard-api-python/README.md)
- [Call Forwarding (Python)](https://raw.githubusercontent.com/team-telnyx/telnyx-code-examples/main/call-forwarding-python/README.md)

## Resources

- [Call Control Guide](https://developers.telnyx.com/docs/voice/call-control)
- [Telnyx Developer Docs](https://developers.telnyx.com)
- [Telnyx Portal](https://portal.telnyx.com)

## API Reference

### `GET /health`

Health check endpoint.

```bash
curl http://localhost:5000/health
```

```json
{"status": "ok"}
```

## Why Telnyx

Telnyx is an **AI Communications Infrastructure** platform — voice, messaging, SIP, AI, and IoT on one private, global network.