| 摘要 |
PROBLEM TO BE SOLVED: To obtain a communication system that uses a signal used for communication such as a speech in a network so as to detect a fault in each device connected to the network. SOLUTION: A call controller 31, a gateway 13 acting like a connector for a plurality of networks, a VoIP phone 15 and a subscriber converter 17 are all connected to a LAN 11. When a call arrives in a VoIP phone system via a telephone network 14 by designating e.g. an existing phone 16 for a destination, the call controller 31 transmits an incoming call instruction signal to the subscriber converter 17 and discriminates the absence of a fault in the subscriber converter 17 when the converter 17 returns an incoming instruction acknowledgement signal. When the identification instruction acknowledgement signal is not returned even once within a prescribed period, the call controller 31 transmits a periodic diagnostic signal to the subscriber converter 17 and discriminates a fault when the controller 31 receives no reply in response to the periodic diagnostic signal. Since the communication system uses a signal usually used for communication except the periodic diagnostic signal, the load on the network can be relieved.
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