You can connect the devices to your local network via a switch/hub or directly with a router. A VoIP PABX is required for Internet telephony. This must be accessible via the local network and must have network access (to the Internet and/or the analogue or ISDN telephone network).
You also need a PC connected to the local network, so that you can configure your telephone system via the web configurator. For each device to be connected to the local network an Ethernet cable (Cat 5/6/7 with 2 RJ45 modular jacks) is required.