 As of 2015 ISDN is being phased out by most major telecommunication carriers throughout Europe in favour of all-IP networks, with some expecting complete migration by 2025
Originally having started as an organization's manual switchboard or attendant console operated by a telephone operator or just simply the "operator", PBXs have evolved into VoIP centers that are hosted by the operators or even manufacturers.Even though VoIP is considered by many people as the future of telephony, the circuit switched network remains the core of communications, and the existing PBX systems are competitive in services with modern IP systems.Five distinct scenarios exist