I was adding a new E1 link to with the remote site. When I try to get the local loop from DDF panel , I could not get the loop. The E1 cable from AR46-80 in patched on DDF panle where it is also patched to tansmission system. While configuring new E1 link I could not get the local loop but also I was getting CRC errors in this E1 interface.
NO alarm was observed in log files.
When I cnage the setting to 120ohm impedence and check again by giving loop from DDF then I got the loop and also CRC errors are removed. I also check the line prtocol by connecting the E1 on transmission media and line protocol was also UP. So the problem is sovled after DIP switch changes.
In the process of troubleshooting, I start checking from hardare side first. All the DDF panels installed at all Callmate TELIPS site were os 120ohm impedence. In the precess I plugged out the board with the problematic E1 and check its hardware status and compare it with one of the correctly running boards. Then I notice the DIP switches on the boards which have different configurations. Then through Card and Interface Manual I come to know that in AR46-80 4E1 card we can configure the E1's in both 75ohm and 120ohm impedences. Then I follow the DIP switch settings described in the mannual and change them to 120ohm settings.
At the time of configuring E1's, one must care about the impedence settings of the E1 interface because bydefault the settings are 75ohm impedence and they have to be chanegd for 120ohm E1 cables accordingly.
Change the DIP switch settings according to 120ohm impedence.