Abstract: A trunk carries out mutual exchange of voice data and MAC frames used in a public telephone circuit. A SLIC carries out mutual exchange of voice data and MAC frames used by PBX telephone devices. Internet protocol telephone devices conduct communications using MAC frames. A LAN switch houses a trunk, SLIC, and Internet protocol telephone devices, and switches ports in accordance with the destination address contained in a MAC frame. A main CPU executes communications protocols for call origination processing, call reception processing and disconnection processing, by communicating with the trunk, SLIC and Internet protocol telephone device.

Abstract: An IP (Internet Protocol) conference telephone system feasible for an IP-PBX (Private Branch Exchange) includes a communication control connected to an IP network. When a connection for a conference is set up between a plurality of telephones accommodated in the IP network, each telephone packetizes a voice signal and sends the resulting packet to the network to address it to a conference trunk. An IP bridge interconnected to the network receives packets via the network 10, multiplexes the voice signals of the packets on the channels of a down-going highway each corresponding to a particular telephone, and sends the multiplexed voice signals to the conference trunk. The conference trunk performs addition and subtraction with the above voice signals and returns the results of addition and subtraction on an up-going highway. This allows a conference to be held between the telephones. A multicast router may be substituted for the conference trunk, in which case the network will be adaptive to multicast.

Abstract: In a packet switching system, a source node divides a variable length packet into a plurality of cells having a predetermined length, and sequentially sends the cells toward a destination node via a first bus controller accommodating the source node, an ATM (Asynchronous Transfer Mode) switch, and a second bus controller accommodating the destination node. The second bus controller detects and stores the last cell from the source node. The destination node generates receive response data for every incoming cell by hardware control to show whether or not the cell has been normally received, and returns the response data to the second bus controller. In response, the second bus controller generates a response cell by hardware control and returns it to the source node via the ATM switch and first bus controller. This allows the source node to determine rapidly whether or not the receipt at the destination node is normal cell by cell.