Noise is heard in incoming and outgoing calls made through narrowband trunks

Hi, everyone!

Good day to you!

This topic describes the solution to noise is heard in incoming and outgoing calls made through narrowband trunks.

Symptom

Version: U1960 V100R001C01SPC200

Network: PSTN–(PRA)–U1960–POTS user

In an incoming or outgoing call made through the PRA trunk on the U1960, both the calling and called parties hear loud noise. Voice is normal in intra-office calls between users under the same ASI board.

Possible Cause

• The parameter setting is incorrect.
  

• A fault occurs at the peer end.
  

• The MTU is faulty.
  

Solution

1. Run the show mrsparas command to check the MTU setting. It is found that the TdmCodec parameter (codec) is set to ulaw.
   

2. Run the config modify mrsparas tdmcodec alaw command to set the TdmCodec parameter to alaw.

3. Perform the dialing test. The fault is rectified.

Suggestions

The E1 standard uses A-law codec while the T1 standard uses the μ-law codec. If the local end and peer end do not use the same codec, noise will be heard. Previously, users can modify parameters using only the CLI. Therefore, the customer generally will not modify the codec parameter by mistake. Now, the LMT, a very easy-to-use tool, is available for modifying parameters. When noise faults occur in narrowband outgoing calls, first check the codec configuration.

Thanks for reading!