| 摘要 |
PURPOSE:To detect quickly whether generation of a fault exists or not, by constituting so that a terminal station which is in a faulty state when a fault detecting channel sent out from a central station is passing can write the faulty state in a prescribed bit of this channel. CONSTITUTION:When checking a fault, a fault detecting fixed channel ALM CH is sent out in a clear state from a central device 100, and passes through each terminal station 101-10n. In this case, a terminal station in which a fault is generated writes a 1 level signal in at least one of a fault collecting bit NO CHG ALM and an important fault collecting bit CHG ALM in accordance with a degree of importance of its fault. In case when a fault is generated in plural terminal stations, write of the fault is executed under an OR condition, and it passes through all the terminal stations and returns to the central station. Since this time is extremely short, the fault detecting time can be shortened comparing with a successive polling system to all the terminal stations. |
