PBXnSip

Pbxnsip is a software implementation of a telephone private branch exchange (PBX) produced by a company of the same name. Like any PBX, it allows attached telephones to make calls to one another, and to connect to other telephone services including the public switched telephone network (PSTN) and Voice over Internet Protocol (VoIP) services. Its name is a combination of the acronyms PBX and SIP (Session Initiation Protocol).