Version 7.0 225 Mediant 3000
User's Manual 15. Media
15.5.2 Enabling IP-to-Tel Call Disconnection upon Detection of
Answering Machine
The device can disconnect an IP-to-Tel call upon detection of an answering machine on
the Tel side. Once detected, the device disconnects the call after the receipt of an ISDN
Connect from the Tel side and then sends a SIP BYE message to the IP side to disconnect
the call. You can enable this feature for all calls (globally) using the AMDmode parameter,
or for specific calls using IP Profiles where the IP Profile parameter 'AMD Mode'
(IpProfile_AmdMode) is set to [1] Disconnect on AMD (see ''Configuring IP Profiles'' on
page 391).
15.6 Automatic Gain Control (AGC)
Automatic Gain Control (AGC) adjusts the energy of the output signal to a required level
(volume). This feature compensates for near-far gain differences. AGC estimates the
energy of the incoming signal from the IP or Tel, determined by the 'AGC Redirection'
parameter, calculates the essential gain, and then performs amplification. Feedback
ensures that the output signal is not clipped. You can configure the required Gain Slope in
decibels per second using the 'AGC Slope' parameter and the required signal energy
threshold using the 'AGC Target Energy' parameter.
When the AGC first detects an incoming signal, it begins operating in Fast Mode, which
allows the AGC to adapt quickly when a conversation starts. This means that the Gain
Slope is 8 dB/sec for the first 1.5 seconds. After this period, the Gain Slope is changed to
the user-defined value. You can disable or enable the AGC's Fast Mode feature, using the
ini file parameter AGCDisableFastAdaptation. After Fast Mode is used, the signal should
be off for two minutes in order to have the feature turned on again.
The following procedure describes how to configure AGC using the Web interface:
 To configure AGC using the Web interface:
1. Open the IPMedia Settings page (Configuration tab > VoIP menu > Media >
IPMedia Settings). The AGC parameters are shown in the figure below:
Figure 15-9: AGC Parameters in IPMedia Settings Page
2. Configure the following parameters:
• 'Enable AGC' (EnableAGC) - Enables the AGC mechanism.
• 'AGC Slope' (AGCGainSlope) - Determines the AGC convergence rate.
• 'AGC Redirection' (AGCRedirection) - Determines the AGC direction.
• 'AGC Target Energy' - Defines the signal energy value (dBm) that the AGC
attempts to attain.
• 'AGC Minimum Gain' (AGCMinGain) - Defines the minimum gain (in dB) by the
AGC when activated.
• 'AGC Maximum Gain' (AGCMaxGain) - Defines the maximum gain (in dB) by the
AGC when activated.
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