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  • Setting up a Snom DECT Base of the M-SC-Series on a FritzBox


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To anticipate this, a FritzBox can easily act as a SIP registrar and thus integrate VoIP telephones in the same way as ISDN or analog telephones, in the past. Unfortunately, the FritzBox's range of functions is not comparable to that of a professional telephone system (PBX).
This article is based on a test on a FritzBox 7590 with Fritz OS version 7.20. It was tested on a Telekom All-IP connection.

1) Connecting FritzBox to DSL

The cables and adapters supplied with the FritzBox differ depending on the product variant.
Therefore, take the cabling according to the scope of delivery of your FritzBox as in one of the two following sections described above.

Connect FritzBox to DSL via DSL cable (TAE/RJ45)

  1. Plug the RJ45 plug of the DSL cable into the "DSL/TEL" socket of the FritzBox.

  2. Plug the TAE plug of the DSL cable into the socket of the TAE socket labeled "F" (see Fig. 1). 

    Fritzbox 7590

    Fritzbox 7390

Connecting FritzBox to DSL via DSL adapter

  1. Plug the long end of the DSL/telephone cable into the "DSL(/TEL)" socket of the FritzBox.
  2. Insert the short grey cable end into the grey DSL adapter.
  3. Plug the DSL adapter into the socket of the TAE socket labeled "F".
  4. Leave the black cable end free (see illustration).

2) Setting up Internet access

  1. Call up the FritzBox user interface in your internet browser of choice (Firefox, Chrome, IE). The user interface can be accessed either via or the IP address of the FritzBox (in the factory settings In addition, the FritzBox can always be reached via the emergency IP
  2. A new Fritzbox is delivered with a secure password. You can find the password on the enclosed note sheet, at the Fritzbox. If you want to change the password, you can do so under "System / Fritz!Box users".

  3. If the wizard for Internet access does not start automatically, click on "Wizard", and then click on "Set up Internet access".

  4. Select "Telekom" in the combo box and click "Next". If "Telekom" cannot be selected, first select "Other Internet providers" and then "Telekom".

  5. Enter the access data you have received from Telekom in the respective input fields and click "Next".

  6. Activate the option "Check Internet connection after saving the settings" and click "Next".

  7. Now the FritzBox establishes the Internet connection with the entered access data.
    The setup is complete when the message "Internet connection verification successful" is displayed.
    Afterwards you will find your access data under the menu item: Internet/Access data

3) Setting up Snom IP-Phone

The configuration of a VoIP telephone at the FritzBox is basically relatively simple.

  • In the first section (3.1) we will first explain how a VoIP phone (regardless of whether DECT or Deskphone) is created in the FritzBox.
  • In the second section (3.2), we will go into how the configuration looks like on the Snom page.

3.1) Step by step instructions - FritzBox:

  • Click on "Telephony" in the menu on the left and select "Telephony device".
  • Click on the far right point: "Set up new device".

  • Since the desired telephone (with and without answering machine) is already selected by default,
  • simply click on "Next" on the far right here.

  • Next select the item: "LAN/WAN (IP phone)".
  • Name the new phone with a unique name.
  • Then click on "Next" again.

  • Now assign a "user name" and a "password". (The assigned phone number can also be used as user name if you want.)
  • Then click on "Next".
  • The user name should have at least 8 characters.
  • AVM changed the password rules. Now it has to be more safe. And it is no longer important how long it is, but i should have a combination of lower and upper case letters, numbers and special characters as usual. (Tested on a Fritzbox 7590 - FW Version 07.12)

    Older Entry from 2018: The password must have exactly 8 characters, no more and no less.)

You should only allow registration from the Internet if you really need it. This is not necessary for an IP phone behind the Fritz Box and should therefore remain deactivated for security reasons.

  • Select the phone number you want to use for outgoing calls.
  • Then click on "Next"

  • Now select the phone number under which the new telephone is to be reached (usually the same phone number as the outgoing number).
  • Then click on "Next"

  • Check in the summary if everything looks correct.
  • Then click on "Next".

  • To complete the process, a "popup window" will appear asking you to do this with an existing telephone 
    to confirm the legality of the setup process. This prevents external users from misusing your FritzBox for their own purposes.
  • If you don't have another phone just press the FritzBox button on your FritzBox. (See link in popup window).

  • Once the process has been successfully completed, you will receive another "Popup Window" as confirmation.

  • After successful setup, the new Snom Phone should now be available under "Telephony Devices", and can be configured there at any time. 

3.2 Step by step guide - Snom DECT base:

With the setup of the Fritzbox most of the setup is done. Now you only have to set up the DECT base.

Please check in advance that your phone has the latest stable firmware version installed.

Enter Snom Webinterface 
  • Pairing handsets

First you should pair the handsets with the base as described in the M215 - SC description. How this works can be found here in the manual on page 25.

  • Rename Handset

In order to better distinguish the handsets from each other, it is possible to change the name. This name will be shown on the display of the handset.

To do so, navigate in the web interface of the M215-SC to the menu item "System" and then to "Handset Name".

  • Create accounts

Unlike the DECT M series devices, the account information of the M-SC series devices is not divided into server and SIP extension. For the M-SC bases, a separate account is created for each phone number. Which handset responds to which number can be read in the next section. Of course the number assignment also depends on the number you have assigned to the account in the Fritzbox.

To configure the M215-SC to connect to the Fritzbox, please follow the steps below:

  • First select the menu item "System" at the top of the navigation:
    • Select "Account 1" and activate it by checking the box "Enable Account".
    • Fill out the marked fields.
      • Account label = This is only the name of the account. It appears as "Line name" under "Line" in the Handset.
      • Display Name = The Display Name is the text part of the Caller ID that is displayed for outgoing calls with Account x.
      • User Identifier = The User ID, also known as Account ID, is a SIP URI field used for SIP registration. Do not enter the host name (for example, ""). The WebUI automatically adds the default host name.
      • Authentication Name = This should be the same name as the username in the Fritzbox. (If authentication on the server is enabled, enter the Authentication Name (or Authentication ID) for authentication with the server)
      • Authentication Password = Here the same "password" as in the Fritzbox comes in.
      • Server Address und Server Address =  Here you enter the "Registrar", either the "IP address" of your Fritzbox or simply "".

  • Save it at the bottom of the page.

  • The first handset should now work.

  • Assign account to handset

In the web interface of the M215_SC you can also set which handset should respond to which number. To do this, navigate to the menu item "System" and then to "Account Assignments".

4) Set up Snom DECT handset of the M-SC series directly on the Fritzbox

The configuration of a M15-SC on the FritzBox is also very easy. In our example we assume that you have just unpacked the FritzBox and no DECT device has ever been connected. Since there are differences in the Fritz OS version, I will also briefly explain this. This guide was created with Fritz OS 7.20. If you don't find certain functions in an older version, please ignore it.

  • Navigate in Fritz OS version 7.1.2 to the menu item "DECT/ Base station".

  • In Fritz OS version 7.2 you will find the menu item "DECT" below "Telephony". Here you can activate the DECT function of your Fritzbox.

  • Before you do this, please scroll down a bit to the "Security" item and change the value there to "Allow non-encrypted DECT connections".

  • Now activate the DECT base by checking the box "DECT base station active" at the top of the page under "Activate DECT base station". And clicking on "Accept" at the bottom right.

  • The Fritzbox will tell you that no DECT handsets are connected and will ask you to add a device. So click on the message and the following window "Register cordless phone (DECT)".

  • A progress bar appears.

  • As soon as the progress bar is visible, press NEXT on the M15-SC and then the hash key. As far as it is an unregistered handset. You can recognize this by the fact that the display of the M15-SC already shows the following:
    Press and hold HANDSET LOCATOR key at base for 4 seconds
    Underneath this is the "NEXT" button.

  • If everything worked fine the following display appears on the Fritzbox page and the handset answers with a confirmation tone and the word "Registered" appears on the display.  

    If the prompt to enter a code appears instead, the registration has failed. Just press the green accept key and put the handset back into pairing mode with "NEXT" and the hash key for a new attempt.

  • Then the Fritzbox checks the DECT phone.

  • Followed by a test ringing on the handset.

  • Once you have answered "Yes" to the question, you can enter a name for the handset. The name will not be displayed on the M15-SC, but for internal calls it will be used to show the called party which device is calling.

  • Then you can select the phone number you want to use with the DECT device.

  • On the next page you can select whether the handset should react to all phone numbers of the Fritzbox or only to certain ones.

  • A summary follows at the end.

  • In the overview the new DECT handset now appears as follows.

For direct configuration of a snom phone on any other router (without SIP registrar feature) on a telecom line they need a different configuration:

For a standard All-IP connection of the Telekom it is the following :

  • User name: (telephone number with area code)
  • Password corresponds to PPPoE password
  • Registrar:
  • Outboundproxy:;transport=tcp (Mostly optional)
  • If required a STUNS server (optional) = Stunserver:

Telephony Features

In this section we would like to show you the most important phone settings and functions. This is to be understood as a very small look into the manual. A detailed manual can be found here:

Change language

If you want to change the language of your handsets from the standard English language, e.g. to German, this can be easily done by any user directly on the handset.

  • Just press the "MENU" button on your M15-SC, then "User Settings" and then "Language". There you can select the language.

Forward calls:

One of the most important telephony functions, especially in companies, is the possibility to forward a call to another phone. This is also called "Call Transfer". In the following I describe how you can transfer incoming calls to another subscriber with an M15-SC.

Attended transfer

  1. Press the  button in the upper left corner of your M15-SC. The call is automatically put on hold and the "Transfer to" screen appears.

    1. Select "A handset party" if you want to transfer the call to another handset registered at the same basestation.

    2. Select "A new party" if you want to transfer the call to any other number.

  2.  With your selection highlighted, press .

  3. Dialing the third party:
    1. If you selected "A handset party", you will see the Intercom screen. Select a handset from the list and press or  to dial.

    2. If you selected "A new party", you will see the message "Transfer to" on the display (Fig. 2). Enter the number you want to transfer the call to; the label  appears on the screen (Fig. 3). Press or to dial.

  4. When the third party answers, announce the call.

  5.  If the third party wants to accept the call, press or . When the call has been transferred, you will see the "call transferred" message.

Blind transfer

  1. PressThe call is automatically put on hold, and the "Transfer to" screen appears.

  2. With "A new party" highlighted, press .

  3. Press .

  4.  Enter the number you want to transfer the call to and press  or to dial.

  5. When the call has been transferred, you will see the "call transferred" message.

    Note: This does not mean that the third party has answered the call, merely that it is now ringing there.