Abstract: A line concentrator used in a ring network system which has line concentrators for accommodating ring lobes, and a ring trunk cable connecting adjacent line concentrators, wherein a signal transmitted from an upstream line concentrator is sent via the ring trunk cable to the ring lobes of an immediately downstream line concentrator. The line concentrator is provided with a circuit for regenerating a signal on the ring trunk cable received by the line concentrator, and repeating and sending the regenerated signal to the ring lobes.

Abstract: A regenerative repeater for regeneratively repeating a signal to be transmitted is inserted in two ring-like transmission lines, and is provided with loop back means for automatically separating the regenerative repeater from the ring-like transmission lines in the condition that a power supply is in a not-yet-turned-on state, so that closed ring-like transmission lines are formed in the form where the regenerative repeater is removed in the condition that the power supply is in the not-yet-turned-on state.

Abstract: In a ring network system including two transmission lines transmitting a signal in directions opposite to each other, and a plurality of line concentrators connected in the form of a loop by the two transmission lines and each accommodating a plurality of terminal stations connected to one of the two transmission lines, a signal detecting unit and a terminating circuit are disposed in each of the line concentrators on the signal output side of each of the transmission lines so as to be connectable to and disconnectable from the transmission lines, so that, when the signal detecting unit in one of the line concentrators is connected to the associated transmission line, the transmission line is disconnected in the line concentrator, and the terminating circuit is connected to the downstream segment of the disconnected transmission line.

Abstract: A ring network system in which a plurality of line concentrators each having terminal stations connected thereto through respective branch lines are interconnected through at least one ring transmission lines. Each line concentrator includes configuration control switches capable of disconnecting from the ring transmission line all the branch lines placed under control of the line concentrator while holding the ring transmission line in the state to allow communication. The branch line(s) disconnected from the ring transmission line form(s) a local ring through cooperation with an internal transmission line. The line concentrator detected abnormality of communication or the line concentrator to be set to the rest state can undergo internal diagnosis operation or continue to be in the rest state without disturbing the communication among other line concentrators.

Abstract: In a ring communications system including a plurality of line concentrators that are connected in the form of a ring, the line concentrators are connected together via a main ring, and the terminal stations connected to the line concentrators are connected to the main ring via ring subsidiaries. The main ring and the ring subsidiaries are connected together via ring connection switches that so work as to connect or disconnect the main ring and the ring subsidiaries. The ring connection switch is so constructed as to maintain the connected condition even when the power source of the line concentrator is in the turned-off state.

Abstract: A station diagnosis method in a communications network system including a closed ring transmission line and a plurality of data stations which can be connected to the ring transmission line by a plurality of line concentrators disposed in the ring transmission line wherein an internal ring transmission line is formed in the line concentrators so that the operation states of the line concentrators are diagnosed by transmitting diagnosis data through the internal ring transmission line.