| 摘要 |
PURPOSE:To improve the reliability of a duplex system by selecting a current or stand-by device in accordance with the coincidence or inconsistency of the switching control output states of respective devices and inverting the switching control output states. CONSTITUTION:Control relays 1CR, 2CR indicating the state of switching control outputs are connected to the 1st and 2nd data transmission devices 1, 2 having equivalent machines respectively and a common switching circuit is constituted of their contacts, a manual switch 3 and a switching relay CHR. Receiving inputs R of respective devices 1, 2 are connected in parallel with each other and then connected to a transmission line 4 and transmitting outputs S are selectively connected to the transmission line 4 through a contact CHR' of a switching relay CHR. The receiving and transmitting outputs are connected to the transmission line in common to monitor the transmitting state by the stand-by device 2. Consequently, respective devices 1, 2 execute both self- checking and monitoring of abnormality of the other device and at the detection of abnormality, the current device is switched to the stand-by device. |
