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

# Switch a voice agent to speech to speech

> Turn on speech to speech for the voice agent Nelly Voice, review the voice prompt, and test a voice call in your browser.

> [!NOTE]
>
> **Intermediate** · 20 minutes · Voice

Speech to speech lets a voice agent hear and speak directly, without separate speech-to-text and text-to-speech providers. In this tutorial, you turn it on for the voice agent Nelly Voice and test it with a voice call in your browser.

> [!NOTE]
>
> Speech to speech is an experimental feature. Settings and behavior can change.

Two models work together:

| Model | What it does |
| - | - |
| **Voice model** | Hears and speaks with the caller directly. |
| **Delegation model** | Handles the agent's tools, skills, and reasoning. |

## Prerequisites

Complete the following prerequisites:

* The voice agent Nelly Voice. To create the agent, follow [Getting started with voice agents](https://docs.cognigy.com/tutorials/voice-gateway/getting-started-with-voice-agents.md).
* An LLM that uses the model `gpt-live-1`. To add an LLM, go to **Manage > AI & Voice Providers** in your project. For details, see [LLMs](https://docs.cognigy.com/ai/agents/develop/gen-ai-and-llms/llms).
* A browser with microphone access allowed. The test call uses your microphone.

## Steps

**1. Open the agent**

1. In the navigation menu of the project, go to **Design > Agent** and open **Nelly Voice**.
2. Go to the **Configuration** tab. The **LLM** and **Voice** sections show the model and speech providers that the agent uses.

**2. Turn on speech to speech**

1. Find the card labeled **Experimental**. The card says that the agent hears and speaks directly.
2. Turn on the toggle in the card.

The **Voice model**, **Delegation model**, **Agent voice**, and **Voice prompt** settings replace the **LLM** and **Voice** sections.

**3. Choose the models and the voice**

1. From the **Voice model** list, select an LLM that uses `gpt-live-1`, for example, **GPT Live**.
2. From the **Delegation model** list, keep the preselected model.
3. From the **Agent voice** list, select a voice, for example, **Marin**.

![Speech to speech settings with the voice model GPT Live, the delegation model, the voice Marin, and the Voice prompt card.](https://mintcdn.com/cognigy-15abf2ba/E7J_TZl63DS6FFRh/_assets/tutorials/speech-to-speech/speech-to-speech-settings.webp?fit=max\&auto=format\&n=E7J_TZl63DS6FFRh\&q=85\&s=1f3a0d841896c4628a5a1bff60b89dbc)

**4. Review the voice prompt**

The voice prompt is the full prompt that the voice model follows.

1. In the **Voice prompt** card, click **Open voice prompt**. The **Voice prompt** page opens.
2. Read the **Prompt template**. The **Prompt outline** lists the template sections: **Backchannel policy**, **Interruption policy**, **Delegation policy**, **Opening**, **AI Disclosure**, and **Language**.
3. Find the `# Opening` section. By default, the agent speaks first when the call connects. It introduces itself by name as an AI assistant and asks how it can help.
4. *(Optional)* To change how Nelly Voice opens the call, edit the text under `# Opening` and click **Save changes**.

![The Voice prompt page with the Edit and Preview switch, the Prompt outline, and the prompt template that starts with the agent name variable.](https://mintcdn.com/cognigy-15abf2ba/E7J_TZl63DS6FFRh/_assets/tutorials/speech-to-speech/voice-prompt.webp?fit=max\&auto=format\&n=E7J_TZl63DS6FFRh\&q=85\&s=e2958aea70c8dede19fb2b845db8a300)

> [!NOTE]
>
> The voice prompt doesn't include the **Instructions** from the **Configuration** tab. The **Voice prompt** page notes that the **Instructions** go to the backend model.

**5. Save the agent**

Go back to the **Configuration** tab and click **Save changes**.

**6. Test the agent with a voice call**

1. To open the interaction panel, click the chat icon in the upper-right corner.
2. At the top of the panel, select **Voice**.
3. Click **Start a call**. If your browser asks for microphone access, allow it.
4. Listen to Nelly Voice. The agent speaks first. For example, it says: "Hi, I'm Nelly Voice, an AI assistant. How can I help you today?"
5. Ask a question, for example, "What can you help me with?"
6. Interrupt the agent while it speaks. In speech to speech, the agent might not stop speaking right away. By default, the voice prompt tells the agent to ignore short sounds such as "mm-hm". It listens when you start a new request.
7. End the call in the interaction panel.

The call runs in your browser. Any action in voice mode ends the current session and starts a new one.

![The interaction panel with Voice selected and the Start a call button below the agent avatar of Nelly Voice.](https://mintcdn.com/cognigy-15abf2ba/E7J_TZl63DS6FFRh/_assets/tutorials/speech-to-speech/test-panel-voice-call.webp?fit=max\&auto=format\&n=E7J_TZl63DS6FFRh\&q=85\&s=0e34b2a521192c32870f164e2bcb8c33)

> [!TIP]
>
> To switch back to speech-to-text and text-to-speech providers, turn off the toggle on the **Configuration** tab and click **Save changes**.

## What you built

You switched Nelly Voice to speech to speech. You chose the voice model, the delegation model, and a voice, reviewed the voice prompt, and tested the agent with a voice call.

## More information

* [Getting started with voice agents](https://docs.cognigy.com/tutorials/voice-gateway/getting-started-with-voice-agents.md)
* [LLMs](https://docs.cognigy.com/ai/agents/develop/gen-ai-and-llms/llms)