the network diagram is
U1960 version is V100R001C01SPC200
now if the POT user call to PSTN, then caller and callee both party hear the noise when talking. if make the internal call, no problem.
1. depend on the testing scenario, we doubt the issue is related with trunk resource board---MTU.
2. do the command:
we can see the TDM codec is ulaw.
3. but actuallly custom use E1 not T1 to connect PSTN. do the command on PBX:
config modify mrsparas tdmcodec alaw
4. test again, no problem
actually custom use E1 not T1 to connect to PSTN. as for PBX, if use E1, the tdmcodec is alaw, it use T1, the tdmcodec is ulaw.
before testing, check the actual network enviroment and PBX configuration.