Duplex transmission path switching apparatus

【Task】 The switching due to a fault, the packet loss or the IP packet, the packet is like when not arrive even after a lapse the predetermined time, is not performed switching if not recognized malfunction. A Present invention has been made in view of the above problems. The first invention is a present transmission path, a transmission failure monitoring unit for monitoring a transmission failure of the present transmission path in the switching device duplex transmission path for flowing the packets constituting the same information to a spare transmission line, the transmission failure monitor arranged downstream of, normal obtains the packet from the transmission path, a switching acquisition unit capable of acquiring packet from the protection transmission path is switched to the protection transmission path in a predetermined case, there result transmission failure monitoring If the result of the a, duplication of the transmission failure has a switch command output unit for outputting a switching capable switch command for switching acquisition unit to the protection transmission line before reaching the switching acquisition unit It relates to a transmission path switching device. .FIELD 1