Patent ID: 7480729

Claim:
A line concentrator having a plurality of communication ports for relaying transmissions of communication data exchanged among network-compatible apparatuses connected through the communication ports, comprising: a response storage portion for storing specific response request information and corresponding response information in association with each other; a destination information storage portion for storing destination information of the network-compatible apparatuses connected through the communication ports individually for part or all of the communication ports; a response necessity information storage portion for storing response necessity information indicating whether it is necessary to perform a specific response operation or not for each piece of the destination information; and a control unit for performing: a communication data judgment operation for judging whether the communication data is a first communication data which can be answered by returning a proxy response, the first communication data containing, as well as the response request information stored in the response storage portion, a destination included in the destination information stored in the destination storage portion and the response necessity information indicating that it is necessary to respond, a second communication data which can not be answered by returning a proxy response, the second communication data not containing the response request information stored in the response storage portion, or an unanswerable communication data other than the first and second communication data; a transmission prohibit operation for prohibiting signal transmission to the communication port connected to the network-compatible apparatus corresponding to the destination information for which the response necessity information indicates that it is necessary to respond in the case of the first communication data; and a proxy response operation for transmitting the response information corresponding to the response request information contained in the first communication data to the network-compatible apparatus from which the first communication data has been sent, wherein the network compatible apparatus comprises a signal monitoring section for detecting signal transmission from the line concentrator during a power save mode and causing a power supply to transfer to a normal mode when the signal transmission is detected regardless of signal content.