Patent ID: 8355318

Claim:
A node apparatus having a plurality of interface units interfacing to a transmission line, switch units of a work system and a protection system to switch signals of the transmission line, the node apparatus comprising: a first controller configured to control relieving a failure over at least one ring network to which a network configuration is applied, in the switch units; a second controller configured to include a first storage medium to store first setting information having a threshold value for a path alarm detection applied on a normal operation and a second storage medium to store second setting information having the threshold value for the path alarm detection applied on relieving the failure over the ring networks, and to control selecting one of the first and second setting information in the interface units; and an alarm detector configured to detect a path alarm based on the selected setting information, and wherein the node apparatus interconnects with the at least one ring network, to which a network configuration with one of a Drop and Continue on Protection channel and a Dual Transmission Protection channel is applied to relieve the failure over the at least one ring network.