| 摘要 |
PURPOSE:To distinguish clearly in all stations in a loop as to whether the own station is a loopback test command station or not by inverting a test bit and transmitting the result to a transmission line when the test bit exists in the frame addressed to the own station and the information of an output terminal of the own station connects directly to an input terminal. CONSTITUTION:When a signal from a switch state storage circuit 24 of a test transfer circuit 19 is logical '1', the own station is in the test state, the signal from the switch state storage circuit 24 is selected and the result is sent to a flag setting circuit 21. A coincidence/dissidence circuit 26 compares the signal from a detection circuit 23 and the switch state storage circuit 24 and discriminates whether the signals are coincident or dissident. When the signal from the switch state storage circuit 24 is logical '0', the signal is not compared with the signal from a detection circuit 23 and the signal of the switch state storage circuit 24 is sent to a terminal device reception interface circuit and a terminal device transmission interface circuit directly. When the signal from the switch storage circuit 24 is logical 1, that is,the own station is in the test state, the signal is compared with the signal from the detection circuit 23, and when they are coincident, its inverting signal of logical '0' is sent to command the transmission/reception of normal data.
|
