In a system configured by connecting a printer (2) and a host device (3) to a line concentrator (1), an arrangement is made such that the printer (2) is held in power save mode for a for a long time to achieve power savings. When transferring to the power save mode, the printer (2) transmits internal information to the line concentrator (1). The line concentrator (1) stores this internal information in association with the printer (2). When an inquiry about the internal information is made from the host device (3) to the printer (2), the line concentrator (1) does not transmit this inquiry to the printer (2) but returns a response (proxy response) to the host device (3) by using the internal information stored in the line concentrator (1) itself. This makes it unnecessary to cancel the power save mode of the printer (2) as a result of the inquiry.