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Call control is a function in a business telephone switch or PBX that routes telephone calls to the proper destination. Call control also maintains the connection between two endpoints of a call. It is one of the major categories of communications traffic in VoIP systems.
Call control is also known as call processing.
Call control is a feature of PBX systems which determines where calls are routed and maintains the connections. For example, call control might detect when a call has ended, or can restart a call if it was terminated abruptly. Other phone services, such as call waiting, are implemented in the call control system. Because PBX systems must be reliable, writing the software for call control can be a lengthy process.
Call control is even more complex with the rise of VoIP and unified communications systems in the enterprise. In VoIP systems, call control uses the Q.931 protocol. Modern VoIP systems can include not only voice calls, but videoconferencing, which makes call control even more complicated than in traditional PBX systems.