Hubbell Incorporated
Systems, apparatuses and methods for party line calls among voice over internet protocol (VoIP) telephones

Abstract:

Devices, systems and methods are provided to support a party call with auto-joining function in a communication system for a distributed transport system that employs VoIP technology. A VoIP unit or end point acts as a conference bridge between an operator extension and other end points. A first end point makes a SIP call to the operator and multicasts a mix of its send audio and the received operator audio. Other end points first check for multicast traffic being received before making a SIP call to the operator and, if so, play out the received audio over its speaker and multicast its send audio. The end point initiating the call mixes this subsequent stream into a stream to the operator, effectively acting as the conference bridge to the operator. The other end points are responsible for mixing received multicast streams for their local speaker.