> ## Documentation Index
> Fetch the complete documentation index at: https://www.bolna.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# DTMF (Keypad Input)
> Let callers enter digits on their phone keypad and have your voice agent respond to the input.
## What is DTMF?
DTMF (Dual-Tone Multi-Frequency) is the system behind phone keypad input: the tones produced when a caller presses a digit key (0-9, `*`, `#`).
When enabled, digit presses from the caller are captured and sent to the agent as a text message, which the LLM can read and respond to just like spoken input.
## When to use it
DTMF is useful any time you want callers to enter structured numeric input without speaking it:
* **PIN or OTP verification** -- "Please enter your 6-digit OTP followed by #"
* **Account or order number lookup** -- "Enter your account number and press #"
* **Phone number capture** -- collecting a callback number during a call
* **Confirmation flows** -- "Press 1 to confirm, 2 to cancel"
* **Sensitive input** -- when callers are uncomfortable speaking a number aloud (e.g. a password or card number)
DTMF works alongside speech. A caller can still speak normally between keypad entries.
For branching menu flows ("press 1 for sales, press 2 for support"), use [IVR Inbound Calls](/ivr-inbound-calls) instead. It handles menu routing natively without an LLM.
## Telephony support
| Provider | Support |
| ---------------- | ----------------------- |
| Plivo | Supported |
| Twilio | Supported |
| SIP Trunk (BYOT) | Currently not supported |
| Exotel | Currently not supported |
| Vobiz | Currently not supported |
## Enabling DTMF
### From the dashboard
Toggle on **Keypad Input (DTMF)** in the **Call Tab** of your agent.
### Via the API
Set `dtmf_enabled: true` inside `task_config` when creating or updating an agent:
```json theme={"system"}
{
"task_config": {
"dtmf_enabled": true
}
}
```
## How it works
1. The agent asks the caller to enter digits and press `#`.
2. The caller presses keys on their keypad.
3. Bolna accumulates the digits until `#` is pressed.
4. The digits are delivered to the agent as: `dtmf_number: `
5. The agent responds to the input.
`#` is the termination key. The agent only receives the input after the caller presses it. The `#` itself is not included in the value.
## Writing the prompt
Tell callers to press `#` after their entry, and tell the agent what to do when it sees a `dtmf_number:` message.
**Example prompt snippet:**
```
When you need the caller's phone number, say:
"Please enter your phone number on your keypad and press the hash key when you are done."
When you receive a message starting with "dtmf_number:", the digits that follow are what the caller entered.
Read them back to confirm and proceed accordingly.
```
**What the agent receives:**
```
dtmf_number: 9876543210
```
The agent treats this like any other message in the conversation. It can confirm the value, use it in a tool call, or move to the next step based on it.
## Next Steps
Menu-based call routing with keypad navigation
All call configuration options