Patent ID: 7706268

Claim:
A transmission device constituting a ring network, comprising: add/drop multiplexer means for adding/dropping and cross-connecting signals; a bridge operative in response to a control signal to duplicate a signal from the add/drop multiplexer means to both work and protection routes of the ring network; a switch to selectively provide a signal from either the work route or the protection route to the add/drop multiplexer means; discard information inserter means, responsive to the duplication of the signal by the bridge, for inserting discard information into the signal to be output from the bridge to the work route, the discard information specifying that the signal carrying the discard information be discarded at a receiving transmission device that receives the signal through the work route; discard information detector means for determining whether or not the discard information is included in a signal that has been received via the switch and dropped by the add/drop multiplexer means; and signal discarder means for discarding the dropped signal, depending on whether the discard information is detected by the discard information detector means.