Definition:
Originally, telephone features were provided by telephone central office switching systems, often called CENTREX. PBX systems emerged as customers wanted to have more calling features and control over their own systems. In 1968, the Carterphone Decision allowed customers to "interconnect" to the AT&T telephone network known as the Bell System. In subsequent years, the interconnect industry flourished as new switching system competitors provided customers with their own PBX and key telephone systems. Today, soft switches or telephone systems in software have emerged along with ethernet LAN and VOIP systems as telephones and computers become integrated.