 Using small PBXs for ISDN is a logical step, since the ISDN basic rate interface provides two logical phone lines (via two ISDN B channels) which can be used in parallel.With the adoption of VoIP by consumers, consumer VoIP PBXs have appeared, with PBX functions becoming simple additional software features of consumer-grade routers and switches.Additionally, many telecommunications providers now offer hosted PBX systems where the provider actually hosts the PBX and the phone handsets are connected to it through an internet connection.