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Speakerphone Characteristics
NOTE:
Pressing any button (mute, hold, etc.) on the speakerphone while in
full-duplex mode causes the system to perform the "speech training" test
again. For example, if you press MUTE while in full-duplex mode, when
you release the call from mute, the system will perform the entire "speech
training" test.
To maximize the usefulness of your full-duplex speakerphone, take note of these
following observations about full-duplex speakerphone operation.
The full duplex operating mode requires a small amount of time to adapt
•
to changes in echo; therefore, you should avoid making any movements in
the vicinity—about a one-foot radius—of the speakerphone.
There are certain echo limits beyond which the speakerphone cannot
•
effect canceling. These limits are as follows: room echoes beyond 39 mil-
liseconds (standard configuration) and line echoes beyond 24 millisec-
onds (standard configuration).
The speakerphone may automatically reduce the volume in each direction
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when both you and the distant party talk at the same time (double-talk).
This volume reduction is necessary to control the echoes at high volume
levels. It is possible for surrounding conversations and other sounds to
trigger double-talk even when you are not speaking. This condition may
lower the loudspeaker volume at your speakerphone.
You must adjust the loudness of your voice to match that of the distant
•
party's voice. This action is necessary to cause full-duplex operation to
take place. Sustained double-talk or excessive echo may cause the
speakerphone to drop back into half-duplex operation. This happens
because the speakerphone's echo cancel circuits cannot adapt during the
double-talk situation.
If both you and the distant party are using full-duplex speakerphones, the
•
sensitivity to both echo path changes and volume reduction during dou-
ble-talk is doubled from the sensitivity when just one full-duplex
speakerphone is involved.
104
IP Speakerphone Station User's Guide
GCA70-377
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