Abstract: Wireless line termination units 21 and 22 respectively transmit and receive frames via wireless lines 51 and 52. Line termination units 25 and 26 respectively exchange frames with the wireless line termination units 21 and 22. The wireless lines 51 and 52 are treated as one virtual line. A radio monitoring unit 272 monitors the state of the wireless lines 51 and 52, and in accordance with the redundancy mode, instructs the wireless line termination units 21 and 22 to exchange copy frames with other wireless line termination unit and to abandon received frames. A communication path control unit 273 sets, in accordance with the monitoring result as to the state of the wireless lines by the radio monitoring unit 272, the line termination units 25 and 26 to each be an active system or a standby system. A switch core 271 passes frames to be transmitted to the line termination unit that operates as the active system.