It all started with Voice over Internet Protocol (VoIP). Prior to VoIP, the PBX was totally independent with its own server connected to proprietary endpoints (telephones) over a proprietary network. VoIP enabled telephony to co-mingle with other servers, networks and endpoints.
Telephony grabbed hold of the concept of unified communications (UC) and made “PBX” a legacy term. A single UC client could support voice, voicemail and instant messaging (IM). UC APIs offered communications capabilities to other applications.
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While the UC industry has done a great deal with multi-modal communications, it has not been successful at unifying communications. In many ways, we are more connected and converse more than ever before, but most of these conversations occur outside of the UC suite.