Siemens GIGASET C475 IP - Manual (Page 144)

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Web configurator – configuring the telephone via a PC
Optimising voice quality for VoIP connections
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Sort the voice codecs in the Selected codecs list into the order in which they should be
suggested to the receiving device when a connection is established. To do this, use
the Up and Down buttons.
When establishing a VoIP connection, the phone suggests the 1st voice codec in the
Selected codecs list to the receiving device to begin with. If the receiving device does not
accept the codec (e.g. because it is not supported), the 2nd voice codec on the list is
suggested, and so on.
If the receiving device does not accept any of the voice codecs in the
Selected codecs list,
the connection is not established. An appropriate message will be displayed on the
handset.
Area: Settings for Codecs
To save additional bandwidth and transmission capacity, on VoIP connections that use
codec G.729 you can suppress the transmission of voice packets in pauses ("Silence Sup-
pression"). Then, instead of the background noises in your environment, your caller hears
a synthetic noise generated in the receiver.
Please note: "Silence Suppression" can sometimes lead to deterioration in the voice qual-
ity.
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In the Enable Annex B for codec G.729 field, state whether the transmission of data packets
during pauses should be suppressed when using the G.729 codec, (activate Yes ).
Saving settings on the phone
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Click Set to save the settings for the voice quality.
Voice quality and infrastructure
A Gigaset C470 IP or C475 IP will allow you to make calls with good voice quality via the
Internet.
However, your phone's performance with VoIP – and therefore the voice quality – also
depends on the properties of the entire infrastructure.
The following VoIP provider components are just some of the things that can influence per-
formance :
u Router
u DSLAM
u DSL transmission line and speed
Please note:
– You should only deactivate codecs (put them in the Available codecs list) if there is a particular rea-
son. The more codecs that are deactivated, the greater the danger that calls will not be able to be
established due to unsuccessful codec negotiations.
– With incoming calls, all supported voice codecs are always permitted.
Please note:
You should observe the following for good voice quality:
– When making calls using VoIP, avoid performing other Internet activities (e.g. surfing the Inter-
net).
– Irrespective of the codec used and the network capacity utilisation, please note that voice delays
can occur.