Patent ID: 6917583

Claim:
An information transmission network system comprising: a plurality of node units each accommodating at least one lower-tier terminal, and service transmission lines and protection transmission lines interconnecting said node units; wherein said node units comprise; a normal operating means for transmitting information in the main traffic by setting a main traffic communication path in said service transmission lines and transmits information in the sub-traffic by setting a sub-traffic communication path, if necessary, in said protection transmission lines, a failure detection means for detecting failure in said service transmission lines, and a backup operating means for inserting a predetermined signal, when a failure has been detected by said detection means, at every exit to lower-tier terminals substantially connected to said protection transmission lines and then switches the main traffic communication path set in the failed service transmission lines to said protection transmission lines; wherein the backup operating means in said node units inserts a first predetermined signal at the exit to lower-tier terminals where said sub-traffic communication path is set and inserts a second predetermined signal, which is different from said first predetermined signal, at the exit to lower-tier terminals where no sub-traffic communication path is set; wherein the backup operating means in said node units inserts the AU-AIS signal (Administrative Unit-Alarm Indication Signal) as said first predetermined signal and the UNEQ (Unequipped) signal as said second signal, when said information transmission network system has a configuration conforming to SDH (Synchronous Digital Hierarchy).