Abstract: When a trouble is developed in an IP exchange (TM) 2 or a circuit (network) 5, a backup exchange 6 (backup TM) is switched over from a waiting system to an operating system, and all IP terminals Eqi inside lodgments A, B, . . . N also log out from the IP exchange (TM) 2, and transmit the IP addresses to the backup exchanges 6 (backup TM) inside own lodgment, respectively, and log in there with a result that the extension telephone calls inside own lodgment is made possible by a control of the backup exchange 6 (backup TM), and therefore, even when a fault occurs in the IP exchange or the circuit, the IP terminals inside the lodgment are backed up and the actuations of the IP terminals are continuously operated, and for example, the extension phone calls inside the lodgment can be realized.

Abstract: An object is to provide an IP telephone enabling to grasp the traffic volume on the network under condition except when during communications. The IP telephone 2 or 2A having a LAN port for connecting to a LAN network 5 and for transmitting and receiving packets through the LAN port, the IP telephone comprises, traffic volume measuring section 17 for always measuring the traffic volume of packets through the LAN port; circuit quality level generating section 22 for generating the circuit quality level corresponding to the traffic volume based on the measured result of the traffic volume measured by the traffic volume measuring section; and display control section 16 for displaying the circuit quality level corresponding to the traffic volume generated by the circuit quality level generating section on the screen of the monitor display section 13.

Abstract: When a trouble is developed in an IP exchange (TM) 2 or a circuit (network) 5, a backup exchange 6 (backup TM) is switched over from a waiting system to an operating system, and all IP terminals Eqi inside lodgments A, B, . . . N also log out from the IP exchange (TM) 2, and transmit the IP addresses to the backup exchanges 6 (backup TM) inside own lodgment, respectively, and log in there with a result that the extension telephone calls inside own lodgment is made possible by a control of the backup exchange 6 (backup TM), and therefore, even when a fault occurs in the IP exchange or the circuit, the IP terminals inside the lodgment are backed up and the actuations of the IP terminals are continuously operated, and for example, the extension phone calls inside the lodgment can be realized.