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Fixed-line telephone (IP) and telephone number

On this page:
Learn how to connect your IP telephone and order a telephone number. Find out how to forward calls internally or hide your number.

Connect fixed-line telephone

With new IP fixed network telephony, fixed-line telephones are connected to the Internet-Box instead of a phone socket. You will still be able to use older analogue telephones that are not IP enabled, but will no longer be able to use some of the functions.

HD-Phones from Swisscom

Analogue telephones

SIP telephones/third-party devices

Ordering/assigning telephone numbers

Order a new telephone number

In the My Swisscom (Customer Center) you can order additional telephone numbers (except SwisscomLine plus). Under "Manage products and services" > "Telephony" > "Adjust options".

Residential customers can use 2 telephone numbers, business customers up to 5. If you would like more telephone numbers, please contact us.

Assigning a number to a device


Centro Business

SIP telephones from Swisscom

Suppressing phone numbers

For all calls

If you want to prevent your fixed network number or name being displayed to the call recipient, you can suppress your phone number. You will then appear to the call recipient as an anonymous caller.

For individual calls

If you wish to hide your number for specific calls, enter the following key combination on your fixed-line telephone before entering the phone number: *31, the number to be called, # (e.g. *310449999999#). This additional service is free.

Hiding a mobile number

If you wish to suppress your mobile phone number, enter *31#. You can deactivate the service again by entering the code #31#.

Forwarding calls internally

In-house forwarding

If several telephones are registered on your Internet-Box, you can use them to make free calls between these phones. You don’t need more than one phone number for this. You can, for example, assign the number 201 to your handset in the living room. You can then dial the internal number 201 on the phone in the bedroom to call your phone in the living room. You can assign the internal short numbers to the individual telephones in the web portal (http://internetbox.home or


Making or forwarding calls internally with a Centro Business 2.0 (HD-Phone Nyon, Gigaset SL360HS and Gigaset CL660HX) is also free of charge and does not require additional telephone numbers. However, you do need an additional phone number/line to forward calls on an IP-Phone (e.g. Yealink T46G, Sarnen HD-Phone) with inOne SME Office.


Internal forwarding is possible only from a cordless HD-Phone to another cordless HD-Phone or to an analogue telephone that is connected to phone port 1 or 2 on the Internet-Box.

Forwarding external calls internally

You can also forward an external call to another internal handset. Proceed as follows:


  1. During the call, go to the ‘Options’ menu and select the ‘Forward’ menu item (alternatively, ‘New call’ or ‘Internal call’, depending on model). The INT button can also be used if available.
  2. Select an internal participant or the direct internal number, e.g. 204.
  3. Wait for the internal participant to accept the call.
  4. Go to the “Options” menu > “Forward” (for some models, you may need to select “Connect” or “Forward call”)
  5. The call will now be forwarded to the internal participant and you can end the call.

Frequently asked questions

What should I do if I can’t make or receive calls?

Why don’t I recognise the caller’s number despite the automatic name display?

How can you make calls using the Home app?



Do you have questions concerning our products?

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