VoIP stands for Voice over Internet Protocol and is the technology that transmits speech or other sounds between two points over Internet Protocol.

A telephone exchange (PBX) is called VoIP when it allows a phone to log in and use the PBX functions through the local area network (LAN) or the wide area network (WAN) and no longer through a dedicated network (as for 'traditional' telephone exchanges).

In addition to this advantages, VoIP telephone can be interfaced with traditional lines (FXO, BRI, PRI) using external gateways or specific networks adapters. This way customers  won’t have to make significant changes to their already existing configurations.