Symptom

Hissing noise can be heard prominently on .rin. The hissing noise is consistent while the called party is not yet answering then it comes in and out on the entire conversation. It can be heard most of the time when calling party is not talking. "No vad" and "no comfort noise" are configured on the voice port and VOIP dial-peer. This was experienced by the customer on his environment and was replicated at Cisco lab. There is a POTS line connected to NIM-4FXO or VIC2-4FXO

Conditions

with POTS line connected to NIM-4FXO

Workaround

use hidden command "non-linear mute" under voice-port configuration.

Further Problem Description