Abstract: A bidirectional line switched ring BLSR network connects a plurality of nodes in a ring formed by transmission lines. In the network, in normal operation each node sends a subsequent node address contained in an APS byte of the K1 and K2 bytes in a multiplexed signal overhead to the subsequent node. When detecting a trouble of a transmission line, each node adjacent the trouble sends the address of a node normally connected thereto via the troubled line. The bidirectional line switched ring network control system provides each node with a bypass circuit for the APS byte and an address comparison circuit for comparing the address in the APS byte with a current node address. Each node closes the bypass circuit and receives the APS byte when the result of comparison proves coincident, and opens the bypass circuit and allows the passage of the APS byte when the result proves non-coincident.