| 摘要 |
PURPOSE:To ensure the detection of a faulty point by sending a fault occurrence signal making a sum between counting value of a fault point detection in a signal and a prescribed value as a new fault point detecting counting value to downward devices in receiving a fault occurrence signal from an upper stream device. CONSTITUTION:A terminal equipment (21-2n) not receiving a transmission start signal sent periodically from a master station for a prescribed time or over enters a loop interruption confirming communication, and in this communication, a head terminal equipment at the downstream side to a loop interruption occurrence point sends a fault occurrence signal where a fault detection count is logical 1. The terminal equipments being downward from the head terminal equipment send a fault occurrence signal having a new fault point detecting counting value being the sum of '1' to the fault detecting counting value received from the upperstream terminal equipment at least to the downstream equipments. Thus, the master station 1 can calculate the loop disconnection occurrence point from the fault point detection count in the fault occurrence signal received from the lowermost terminal equipment.
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