3CX - VoIP telephony in the home office

As a new telephony feature, the kiz has put a VoIP telephone system from the provider 3CX into operation. The system is part of the university's system network and is therefore connected to the existing Alcatel infrastructure. The system is operated for the purpose of supporting the telephone accessibility of employees who increasingly work from their home offices, especially during the COVID 19 pandemic. With 3CX, business calls can be made from home via the university. Internal calls between extensions of the university can be made without the use of exchange lines and without the costs that may be associated with this.

3CX is designed for the home office and is therefore not supported in the university environment and should not be used (for capacity reasons).

The service agreement on teleworking applies (Overview of the service agreements - Only available within the university).

Performance features

Upon request, employees receive an additional virtual telephone number to which the business landline telephone can be diverted. When calls are made using this number, the called party is shown the existing Uni office number (or Uni DECT number).

To use it, either an internet-enabled PC (web browser) with a headset or an internet-enabled smartphone (installation of the 3CX app) is required. To avoid additional costs for data usage on private smartphones, it is recommended to deactivate the use of mobile data for the 3CX app (use then only possible via WLAN).

The status (e.g. available, absent, do not disturb) can be set in the 3CX system via the front end (browser on the PC, app on the smartphone). This allows the user to influence the availability from anywhere (smartphone) at any time without needing extra access to the university phone. Calls to and from the university's PBX network are free of charge (internal calls). In addition, calls to the national fixed and mobile network are possible (selected exchange authorisation according to the application). The call charges are billed via the specified cost centre.

The 3CX app (or the WEB client) can be used to call up or change the call forwarding status (instructions can only be called up internally) of the Uni phone  using the speed dial 39999.

User groups

University connections without clinic.

Application modalities

The application procedure is carried out via a collective form for each institution or institute:

  • Contact the helpdesk of the kiz (helpdesk(at)uni-ulm.de) by e-mail and provide the following information via the provided Excel spreadsheet (nutzerdaten.xlsx): Last name, first name, e-mail, existing university phone number, cost center and the desired office authorization. Please use the subject "Homeoffice telephony with 3CX" in the email to enable us to quickly assign the call. Department heads or authorized signatories of the specified cost center will be accepted as senders.
  • If you want to submit the request collectively for several people, you can also fill in the Excel spreadsheet provided (nutzerdaten.xlsx) and send it to us.
  • After the application and set-up by the kiz, the respective employee receives a welcome email with the assigned virtual phone number, a short installation guide and a configuration file or a scan code which is necessary for the smartphone installation.


There are no additional costs for the institution. Any charges incurred for external telephone calls will be invoiced as usual via the University's departmental cost centre.

[Translate to english:] 3CX Logo

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more about: 3CX

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UUlm 3CX Quick Start Guide  (German only)