| 摘要 |
PURPOSE:To execute remote monitor with high accuracy with simple constitution by deciding it that a slave station has a fault by a master station if a normal notice signal sent from each station is not received over a prescribed period. CONSTITUTION:An oscillator 24 is oscillated in different frequencies f1, f2,..., fn for each of slave stations 3-n. A normal notice signal sent from each slave station onto a transmission line 2 is fed to band pass filters 13, 14,..., 1n via a hybrid circuit 11 in the master station 1. Each of the band pass filters 13-1n supplies only the normal notice signal in the frequencies f1-fn sent from the slave stations 3-n to a fault decision circuit 12. A fault decision circuit 13 monitors the interval of the normal notice signal and when it is not detected over a prescribed time T, it is discriminated that a slave station to send the normal notice signal is faulty. |
