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

# Features and Capabilities

<Badge icon="arrow-left" color="gray">[Back to Voice Gateway Advanced Configuration](/ai-for-service/channels#advanced-configuration)</Badge>

This section highlights additional features and capabilities of the Voice Gateway.

## SSML (Speech Synthesis Markup Language)

Using SSML allows developers to control aspects of speech synthesis such as pronunciation, volume, pitch, and rate of speech. Here's a guide on how to use SSML effectively:

### Understanding SSML Basics

* SSML is an XML-based markup language used to control text-to-speech synthesis.
* It provides tags to control various aspects of speech synthesis, including pronunciation, prosody, volume, and more.
* SSML is supported by many speech synthesis systems, including Amazon Polly, Google Text-to-Speech, and others.

### Basic SSML Tags

* `<speak>`: This is the root element of an SSML document and indicates the start and end of the speech content.
* `<break>`: Inserts a pause into the speech synthesis. You can specify the duration of the pause using the `time` attribute.
* `<emphasis>`: Emphasizes a portion of the text. You can specify the level of emphasis using the `level` attribute.
* `<prosody>`: Modifies aspects of speech such as pitch, rate, and volume. Attributes include `pitch`, `rate`, and `volume`.
* `<phoneme>`: Specifies the pronunciation of a word using phonetic alphabet symbols.
* `<say-as>`: Indicates how a particular piece of text should be pronounced, such as numbers, dates, or currency.
* `<audio>`: Embeds audio files into the speech output.

### Using SSML in Code

When using SSML in your code, wrap the SSML markup within `<speak>` tags.

Example:

```SSML theme={null}

<speak>

    Here is a number <w role='amazon:VBD'>read</w>

    as a cardinal number:

    <say-as interpret-as='cardinal'>12345</say-as>.

    Here is a word spelled out:

    <say-as interpret-as='spell-out'>hello</say-as>.

</speak>

```

### Voice Tag Support

#### Support For Voice Elements in SSML

In the speak tag, follow below-mentioned steps:

1. Empty speak tag without attributes **\<speak>**
   1. In this case, Voice Gateway will construct **voice** and **language** elements on its own based on values supplied in Call control params.
2. Customized speak tag with attributes **\<speak version="1.0" xml:lang="en-US" xmlns="**[W3C Speech Synthesis namespace](https://www.w3.org/2001/10/synthesis) **">**
   1. In this case, Voice Gateway will send the SSML without any modifications to the TTS engine. Follow option 2 and the voice element will work.

Example:

```
<voice name="en-US-AvaNeural">Hi, I'm eBay's automated phone assistant. Let me know in a few words how I can help.</voice>
```