Environment: 8620 MCU, E1 network and 8020PLUS terminal. The problem is: In normal conference, host conference site terminal is called continually until call completion. But call is hanged up immediately. Then this process will loop continuously.
According to above analysis, we check whole system circuit diagram and take loopback test from MCU to DDF, no problem. Take supe test from terminal and DDF, disconnecting. When check a distribution frame we find one RJ45 is loose connection. Pull out and plug, then problem disappeared.
The other conference sites can join conference normally. Checking this conference site port condition in local management, we find the conditions in local end and far end step out. Make port internal loop, it synchronizes. So MCU port has no problem. Make port external loop, it steps out. So the line between MCU and this terminal has problem. What’s more, this terminal can be called, so terminal receive line is good. Maybe the send line is unavailable. So, we ensure it is the line between terminal and MCU that has problem.
There are two points:
1. Locate problem rapidly.
2. The complete circuit diagram which is reserved.