The voice network consists of four digital telephone exchanges, located at 80 Karoli & Demetriou (Central Building), 21 Karoli & Demetriou, 150 Androutsou and 122 Karoli & Demetriou, which are connected to the OTE telephone network via ISDN-PRI lines through the telephone exchange of the Central Building. The digital exchanges provide users with features such as the ability to manage three calls simultaneously, call transfer, call forwarding, last number redial, auto-redial, call diversion, call pickup, conference and choice of alert tone. The connection to the Internet (Internet) is established via a leased optical fibre with DWDM technology enabling 1Gbps speed and via a backup line with 64Kbps speed (via FortHnet).
The building at 126 Karoli and Dimitriou is connected to the telephone network of the Main Building by using the data network and VoIP (Voice over Internet Protocol VoIP) technology.