Line concentrator, network-capable apparatus, and communication system

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.