PURPOSE: To allow a user to specify a terminal equipment station having a fault at a glance by detecting the terminal station having the fault automatically among plural terminal stations and displaying the state of the station.
CONSTITUTION: When the occurrence of a fault is discriminated in a branch line 8 of a ring, a line concentrator 1 making the discrimination acts like disconnecting the faulty ring from a trunk line 6. Since the trunk line 6 is a closed ring by the disconnection, a terminal station 5 connected to the ring branch line 8 continues the in-ring communication function. In this case, a fault lamp corresponding to the disconnected terminal station 5 is lighted. Thus, the terminal station having the fault is specified by the user at a glance.
SATO KANICHI
KOMATSU TAKEHIKO
WATANABE TORU
