Telephone System

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The telephone system of CAU is part of the state language network. The operator of the system is Telekom under the Flexport contract.

The Customer Service Center (CSC) for the state network can be reached at
the service number 0800 27 27 400.



There are two IP phone models available to you. The larger Cisco 8851 can be recognized by its color display. The smaller device is the Cisco 7841. Short references and manuals are available for both devices, explaining their operation and functions. The links can be found on the right side of the page.



Faxes are fundamentally no longer part of the state language network contract and cannot be obtained through it. The computing center supports you in connecting fax machines, but there is no guarantee of functionality. Most fax machines work when the baud rate is set to 9600 and ECM (Error-Correction-Mode) is disabled.


Self-administration portal

Many of the configurative options are available to you via a web portal ( From this, you can make settings for voicemail, customize function keys, and manage personal phonebooks, for example. To do this, you need to be in the VPN or on-site in the campus network. To manage your phone, your RZ account (suabc123) must be linked with your phone number. This is not guaranteed for everyone. So if no phone appears for you in the portal, please report your extension and RZ account to us with a request for linking at


Malfunction / Help / Needs

Feel free to contact the CSC directly at 0800 27 27 400 if

  • Your end device (phone, headset, etc.) is defective
  • You have questions about operating your phone or the self-administration portal


In case of doubt about the nature of your request and all other inquiries (new connections, relocations, service bookings, changes, fault reports, material needs, etc.), please direct them to Please always provide the necessary data:

  • Extension(s)
  • RZ account
  • Building
  • Room
  • A precise description of the problem or request


Change notifications

If changes occur to devices (installation location, user, etc.), they are mandatory to report. Please report these in writing and informally to The devices are owned by third parties, and the computing center is obliged to inform the ministry about their position and use!


Old application system

The old web system for applications is obsolete. Please do not submit any more applications through it, but instead informally and in writing as described by email. Also, please do not send any more applications by fax.


Passwords / PINs

There are a total of three passwords for using the phones. The terminology here can be quickly confusing. You need

  • Your RZ account and the corresponding password for the self-administration web portal
  • A phone PIN for using, for example, the personal phonebook, which can be set in the self-administration portal
  • A voicemail PIN for the answering machine, whose default value is 1234


Disposal of old devices

The old phones will sometime be picked up by a subcontractor of a subcontractor of Telekom. It was not possible to get concrete dates for this. The service provider will show up at some point and pick up the phones. You can store the old devices collected somewhere with you or leave them at the place or in the office. However, please do not dispose of them yourself.



Frequently Asked Questions (FAQ)

  • Which phone numbers can not be called?
    • Phones usually have national calling authority. International calling authority requires an informal application. Some phones, e.g., wall phones, can only make internal calls.
  • How do I use the voicemail?
    • The use of the answering machine is described in the phone manuals.
  • Why did my colleagues receive a new phone but I did not?
    • Very likely, your phone was not properly reported. Report it to us informally and in writing as described above.


This list of responsible service supervisors is generated automatically.