The telephone installation at DESY in Hamburg has about 6200 extensions and offers a wide range of communication possibilities with lots of special features. The phone system composes of analogue (push-button dialling phones) as well as digital (ISDN and IP) phones with a voice mail recorder, a fax server and further special functions. The DESY telephone installation in Hamburg is interconnected with those of DESY in Zeuthen and the administration net of Hamburg (e.g. University of Hamburg).
The classic telephone system at DESY in Hamburg consists of an Avaya Integral I55 system. The I55 serves both analog and digital connections. Two remote modules are connected to the I55 via fiber optics. They are located in building 241 (Fon container) and in building XSE. The module in building 241 contains 540 call numbers provided for UNI Hamburg. The remote module with 224 call numbers in the XSE building is exclusively for the provision of analog call numbers in the EXFEL buildings and tunnel areas.
Since February 2005, a VoIP installation based on a Cisco Callmanager has been added to the system as a component. This part of the system already serves over 4500 IP telephones and became the leading system in May 2020 by converting the outside lines to SIP technology. In addition, there is a system interconnection between DESY-Hamburg and DESY-Zeuthen.
A cut-off of the Integral I55 is neither planned nor wanted at the moment, because due to the technical independence of the IP Data net, it is necessary to keep the redundancy of the IP-data. Modern functions such as softphones, outlook-integration, XML-services, video calls are realized primarily on IP phones.
The system network is currently connected to the public telephone network via an encrypted SIP trunk, which means that a maximum of 100 channels are available for external telephone calls. These 100 channels are also used by the Zeuthen Cisco call manager and the UMS server.