LOOP NETWORK SYSTEM

PURPOSE:To build up the loop network in which a time division multiplex frame is adopted and an SDH network is used as a part of a transmission line. CONSTITUTION:A master node 101 branches and inserts line data connecting to its own node to a service channel of a frame and sends the result to a succeeding slave node or an SDH connection node S. A slave node 102 is in subordinate synchronization with a reception frame, branches and inserts line data connecting to its own node and sends the result to the succeeding slave node, or an SDH connection node S or a master node. The master node 101 implements loop delay correction in which a reception C4 data are replaced with transmission C4 data in the unit of frames and in the unit of multi-frames between the received frame and the frame generated by itself, and an SDH network is used via SDH connection nodes 105, 106 for a part of a transmission line between the master node 101 and the slave node 102 or a transmission line between slave nodes.