19.2.3.3. Voice Activity Detection (VAD) 
In order to save bandwidth Voice Activity Detection (VAD) has to be
activated for IP connections. When a DMC is established and VAD is set
only idle frames are sent on the master connection.
VAD is activated with the following AMO commands:
- Station:
CHANGE-SDAT:STNO=<ext. number>,TYPE=DATA1,CLASSMRK=VAD&EC&G711&G729OPT;
- Digital trunks:
CHANGE-TDCSU:PEN=<ltg-ltu-slot-cct),CLASSMRK=VAD&EC&G711&G729OPT;
- Analog trunks:
CHANGE-TACSU:PEN=<ltg-ltu-slot-cct),CLASSMRK=VAD&EC&G711&G729OPT;
- IP trunking:
-
Modifying of codecs and VAD is no longer possible via WBM and any change has to be done via AMO CGWB. However, it is still possible to display the current settings via WBM under Configuration > Voice Gateway > Codec Parameters(The same applies for HG 3575 IPDA - AMO STMIB)
- HFA: VAD must be activated at both ends of the HFA master connection.
-
For IP phones: the silence suppression needs to be checked in WBM of the phone under Administrator > Speech/Cloud > Codec Preferences.For HG 3500:
CHANGE-CGWB:MTYPE=CGW,LTU=x,SLOT=xx,TYPE=ASC,VAD=YES;