Patent ID: 6434142
Filing Date: 2002-08-13
Classification: H04M

Abstract:
A communication system comprising:a local area network (LAN); first and second LAN telephone gateways connected to said LAN; a speech network; first and second private branch exchanges (PBXs) connected to said speech network, said first and second PBXs being connected to said first and second LAN telephone gateways, respectively; first and second telephone sets connected to said first and second PBXs, respectively; means for realizing a first speech path from said first telephone set via said first PBX to said first LAN telephone gateway; means for determining whether a second speech path from said first LAN telephone gateway via said LAN, said second LAN telephone gateway and said second PBX to said second telephone set is possible or impossible, after said first speech path is realized; means for realizing said second speech path, after said second speech path is determined to be possible; means for realizing a third speech path from said first LAN telephone gateway via said first PBX, said speech network and said second PBX to said second telephone set, after said second speech path is determined to be impossible; means for determining whether or not a fourth speech path from said first LAN telephone gateway via said LAN and said second LAN telephone gateway to said second PBX is possible by using a three-way calling system in said second PBX, when said third speech path is realized; means for realizing said fourth speech path, after said fourth speech path is determined to be possible; and means for disconnecting a part of said third speech path from said first LAN telephone gateway via said first PBX and said speech network to said second PBX, after said fourth speech path is realized.