Sensitivity in sending direction can be adjusted in 9 steps
for handsfree microphone and for handset microphone.
Therefore you can choose following hidden page on the web interface of the telephone:
--> open web interface of telephone
--> login with admin account
--> http://<IPadress telephone>/welcome.html change into: http://<IPadress telephone>/voiceadj.html
There are following adjustment parameter:
HandFree MIC TX: actual value, --> adjustments: 0-9
HandSet MIC TX: actual value, --> adjustments: 0-9
Handset AEC: 1 --> 0:Disable, 1: Enable
Increasing the value increases the microphone loudness.
As default now the Automatic Eco-Cancelling (AEC) is activated. AEC should deactivate or minimize an Echo to the earpeace. If there is no improvement or Echo is too high, you should reduce microphone level again.