Help Needed : SS7 Continuity Check With NMS TX Boards

Hello,

For an application that uses NMS TX 3220 boards to handle the SS7 signalling and NMS AG 4000 boards to handle the voice channels, I need to implement the continuity check.

But i can't put a circuit into a loopback mode, can anyone please help/ give any clues?

NMS just said that "loopback should be done with TX board", not any more clues. and i did not find any other info from documentation.

Here is some detail about the scenario

The far end sends IAM packet and then sends COT right after it. And after some seconds REL comes and conversation drops.

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IAM