To make such an ordinary hub as works on the power fed through a power adapter connected to a commercial power supply be capable of maintaining its hub-function without interruption even when a commercial power supply failure occurs. The ordinary hub is connected to a line securement power supply unit 8 that is power-fed from a POE-compliant power-feeding hub 3 through a communication cable 5c, wherein a means for producing a power for an ordinary hub using a power fed through said communication cable 5c so as to feed produced power to an ordinary hub 2; and a storage battery 806, which stores power while power-receiving, to be used as the power source for producing a power for said ordinary hub when a power failure, are provided in said line securement power supply unit 8.