When we get a call in through the Gateway (T1 Multiflex trunk) some calls the voice from the distant end fades in and out.
Do the following .
1. Go offhook in each of the modes (headset, speakerphone, and handset )
2. Check the position of the volume boost slider. If it is too far away from the middle, set it to the middle
3. Run Audio Tuning Wizard to make sure everything sound ok.