| 摘要 |
PURPOSE:To ensure the highly efficient maintenance and checking in a simple constitution, by connecting the main master station to the secondary master station and slave station via the 1st and 2nd up-circuits and then detecting the fault occurring to the up-circuits at the master stations to change-over the circuits. CONSTITUTION:The connection is secured among slave station 21, main master station 22 and secondary master station 23 via up-circuit 24 and down-circuit 25 each. The up-circuit possesses the 1st and 2nd circuits 241 and 242 and is then connected to the both master stations via circuit change-over switches 26 and 27. Slave station 21 is provided in plural numbers, and its transmitting circuit consists of modulator 31, hybrid transformer 32, level adjusters 33 and 34 plus circuit changeover switch 35 each. Adjusters 33 and 34 are controlled so that the transmission signal arriving levels to the both master stations may be equal to each other in accordance with the distances to the both master stations. And now if the fault occurs at point A of circuit 242 and in the state of connection of each switch as shown in the figure, this fault is detected at stations 23, 22 and 21 each. Then the changeover is given among switches 27, 26 and 35 to transmit the signal sent from the slave station to the direction of the dotted line in the figure. In such way, the reception with the steady receiving level is possible at each of the two stations. |
