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

# Telephony connection

> How calls reach your agent: via a phone number or via SIP from your phone system.

An agent can be reached in two ways. Callers dial its **phone number**, or your own **phone system** forwards calls directly to it via SIP. In both cases, the agent answers the call and conducts the conversation according to its active live version.

## Via a phone number

You store the phone number in the agent's basic settings (see [Manage agents](https://docs.msghello.ai/en/agenten-verwalten.md)). It must be registered with our telephony provider. Each phone number belongs to exactly one agent.

The agent also uses the same phone number as caller ID when it [places calls itself](https://docs.msghello.ai/en/ausgehende-anrufe.md).

## Via SIP from your phone system

If you operate your own phone system or contact center, you can hand calls over to an agent via SIP without setting up a separate phone number for it. For this purpose, every agent has its own SIP address.

```
sip:<agent ID>@<SIP domain>
```

* The **agent ID** is the ID of the agent. You find it in the browser's address bar when you open the agent in the portal.
* msg provides the **SIP domain** of your environment.

Your phone system dials this address, for example as the forwarding destination in a queue or a voice menu. If no agent exists for the dialed ID, the call is rejected.

> [!TIP]
>
> This way you can keep an existing service number. The phone system answers the call and hands over only the matching requests to the agent.

## Caller's phone number

With every call, the telephone network transmits the caller's phone number, unless the caller withholds it. msg.Hello stores it with the call. It appears in the [call analysis](https://docs.msghello.ai/en/anrufe-auswerten.md), and the agent can use it during the conversation with the built-in tool [get the caller's number](https://docs.msghello.ai/en/system-tools.md).

For incoming calls, msg.Hello also stores the SIP header `From` as metadata of the ongoing session. It contains the sender address as transmitted by the telephone network or your phone system.


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