Siemens GIGASET C475 IP User Manual

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Web configurator – configuring the telephone via a PC

Optimising voice quality for VoIP connections

Gigaset C470-475 IP / EN for IM-Ost / A31008-xxxx-xxxx-x-xxxx / web_server.fm / 18.12.07

ion 2.

08.0

1.20

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

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.

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

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 :

Router

DSLAM

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.

This manual is related to the following products:

Gigaset C470 IP