| 摘要 |
PURPOSE:To take a return test of a bus transmission line without stopping the communication of each terminal at a center device by returning the maintenance test bit of a down line frame to an up line by a bus terminator installed at the terminal part of the bus transmission line. CONSTITUTION:A multiplex transmission system consists of the center device 1, bus terminator 2 consisting of a relay, etc., terminal devices 3-5, the down line R and up line T of the bus transmission line, and a subscriber line L. A frame on the bus transmission line consists of information channels CHA and CHB, frame bit F, and the maintenance test bis S. For example, the CHs A and B are allotted to the devices 3 and 5 at some communication time. The devices 3-5 synchronise with a frame phase extracted from the bit F sent back from the down line R to the up line T by the terminator 2 to send the bit S to the up line T together with the CHs A and B of the up line, thus taking a return test of the transmission line. |
