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W i n d o w s
P C
S o f t w a r e
ATTENTION
P A GE 4 2
Echo Canceller
An Echo Canceller can be turned on or off for each channel.
Double click with the mouse on the appropriate channel to open the configu-
ration window. To turn the Echo Canceller off, choose Off, to turn the echo-
canceller on, select On.
Use of the Echo-Canceller
In general the use of the Echo Canceller is recommended. Always when a
caller with an analogue telephone calls to the Hybrid there is an echo on the
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channel, which can interfere with the received signal. Digital telephones (e.g.
ISDN or mobiles) do not cause this kind of echo. In this case, an Echo Cancel-
ler probably impairs the incoming signal. For this reason when establishing
the connection the Hybrid sends a short test signal to the caller and measures
the level of the echo. If the set value is not exceeded the Echo Canceller will
be turned off since it is expected that the caller is using a digital telephone. If
the level of the Echo is too high the Echo-Canceller turns on automatically.
However, each Echo Canceller can only cancel echoes if the signal delay lies
within a certain range. Telephone connections via satellite have such a high
range of delay that the Echo Canceller may not operate correctly.
Expander
The Expander adjusts a caller's signal automatically to a lower level when a
certain threshold is reached. With this devise the background noise of callers
who are not actually speaking, is completely filtered.
The Expander is turned on by setting the check mark. The threshold at which
the noise suppression should start is defined in Threshold. The default setting
is -32 dBu.
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