Hitachi, Ltd.

Masahiro Fuse

Jiro Kashio

Susumu Nakayashiki

Takeshi Harakawa

Hiroyuki Wada

Yoshinori Bekki

Osamu Ebina

Hiroshi Nakase

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.

Network system diagnosis system

In a communication network having a plurality of stations interconnected through a double ring transmission line, a station which detects a failure in the ring transmission line sends out a failure notice data, and a station which has received the failure notice data stops the send-out of its own data and relays the received data. A station which cannot receive the failure notice data loops back and transmission line to form a closed ring transmission line which bypasses a failure location.

Ring communication network system and a method for controlling same

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Hadano, Japan

Masahiro Fuse