# What is the mobile extension line?

There are situations where it is sufficient to equip individual people or even devices with mobile service, without having to book or create them as new users in the phone system. This is possible with the feature **mobile add-on line** possible.

For example, you can provide employees who want to be reachable on the move and who can make calls and use mobile data. Alternatively, mobile service can be conveniently set up for devices such as surveillance cameras, alarm systems, and card readers via the mobile add-on line. Several employees can then access these independently of one another.

With the mobile add-on line, unlike with newly created users, **not** the full range of the sipgate phone system can be used. For example, **no voicemail or event list** .

## Where can I find the feature?

The starting point for user-independent mobile service is the [**mobile service tile**](https://app.sipgate.com/mobile-telephony) in the **account management**. Here, click on **book mobile options**.

![sipgate-Hilfecenter-Mobilfunk3.png](/files/9ed1d1db74d099141ef699bb1495518a5427b9f5)\
Then, in the next step, select **mobile add-on line**.

After you have assigned the **device name** , you add a phone number.

{% hint style="warning" %}
**Important:** Please note that for this feature you can **only use mobile phone numbers** . Landline numbers are not available for this feature.
{% endhint %}

If your **Sender number** is to be the same as the previously added phone number, you must enter this in the **device settings** of the corresponding **device card** manually.

![sipgate-help-center-mobile5.png](/files/4622fe472ef696d5c7c8bfd167d110593b3e912e)


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