| 摘要 |
PURPOSE:To attain switching of a duplex transmission line with less hardware, by connecting a transmission control section and a microcomputer fixedly to a modulation and demodulation circuit, and performing the switching of the line constitution with a transmission/receiving circuit part. CONSTITUTION:Multiplexers 46-49 are connected to transmission/receiving circuits 10-13, and the transmission lines are reconstituted by switching the circuits with switching signals SA1, SA2, SB1, SB2 from a network constitution control circuit 55. Since the multiplexers 46-49 are provided to a serial transmission line of signals, the reconstitution is realized with a simple constitution. Further, the transmission control circuit 55 controlling it is simplified. Further, the microcomputer 26 is connected fixedly to a modulation and demodulation circuit 14 of the transmission line of the system A via the circuit 54 and no multiplexer is provided to a parallel signal line 27. The output of the circuits 14, 15 is provided with state detecting circuits 20, 21 detecting the presence of a data signal and connected to the circuit 55 via a multiplexer 53. |
