Technical data

PAGE 90
MAGIC TOUCH Software
FIG. 59 SWITCHING ON AND OFF OF THE AGC AND THE ECHO CANCELLERS
After pressing the OK button, all settings are accepted.
The Cancel key deletes all settings.
Via the Set AGC on/off for all lines key, the AGC can be switched on or off for
all lines.
Equally the Echo canceller can be switched on or off via the Set Echo Canceller
on/off for all lines key.
7.7.3.11.2 Automatic Gain Control Settings
An Automatic Gain Control is only useful when there is the possibility of
making a pre talk with the caller where the correct level can be set.
The setting Threshold defines the level limit from which the signal of the AGC
should be "monitored"(useful value: ~ -32 dB). Otherwise, too quiet signals
(such as rush) would be increased by the AGC.
To avoid steps in the noise level, the AGC control speed should not be set too
high in the Speed of the AGC setting. Likewise, it must not be set too low, oth-
erwise the control will never reach the desired target level. The unit for this is
dB/ms (useful value: ~ 1 dB/100ms).
The AGC nominal level of the Level setting defines the medium level of the
signal, which should be set by the AGC. In the case of a signal without flicker
that lies above the threshold value, this level is set after some 100 ms depend-
ing on the AGC control speed. When selecting the level it should be seen that
this level is not set too high otherwise the hardware related level range is ex-
ceededand distortions occur. A level that is set to low affects the understand-
ability of the caller signal (useful value: ~ -18 dB).
The key Default Settings resets the values for the AGC and of the Expander to
the default settings.
7.7.3.11.3 Expander
An Expander causes that all signals, which fall below a certain threshold to be
completely suppressed. Therefore a rush from the caller side can not be heard
anymore during pauses of the caller. The value of the expander threshold,
called Threshold (useful value: ~ -32 dB) should always be selected in a way
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In the case of satellite connections, where the transmission time of the Audio
signal is quite long , the Echo canceller can not work properly. Because of this,
it is recommended that the Echo canceller is switched off when there are con-
nections with a long transmission time.
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An AGC is no wizard. Callers who are extremely quiet cannot be increased in
any way. Very loud callers can not be decreased in any way.