| 摘要 |
PURPOSE:To attain the communication between a communication controller and all terminals even at a failure of a relay line, by multiplex and concentrating the lines and transmitting a low speed line data connected to the relay line to other relay lines when the quality of a relay line system is deteriorated. CONSTITUTION:The communication controller 1 and terminal devices 9-1-9-n, and 9-(n+1)-9-2n are connected to modem 4, 5, 11, 12 of other systems and relay lines 6, 14 via low speed lines and multiplexing line concentrators 15, 16. A frame monitoring circuit 30 of the concentrators 15, 16 monitors a relay line and if a frame error is detected for a prescribed time or over, the circuit 30 transmits an error detecting signal including the number of low speed line deteriorated by the quality to a control circuit 35 and a control frame generating circuit 31. Thus, the circuit 35 performs line concentration and multiplexing the low speed line of the relay line with deteriorated quality to the line concentrator and multiplexing circuit 25 together with the relay line with good quality, and the circuit 31 generates a control frame and transmits it to an opposite line concentrator. The circuit 30 of the opposing line concentrator detects it and performs the line concentration and multiplexing for the low speed line to the relay line of good quality. |
