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Chapter 5 – Call Control Commands
Multi-Tech Systems, Inc. Wireless GSM/GPRS AT Commands (Document Number S000293I) 27
Echo Cancellation +ECHO
Description: This command enables, disables or configures the Echo Cancellation functions for voice calls (in rooms,
in cars, etc.).
It is necessary to tune the Microphone gain (AT+VGT) and the Speaker gain (AT+VGR) before
activating the Echo Cancellation.
Notes:
• You can activate/deactivate the echo cancellation during a call without resetting the product if
the <Algold> parameter is not changed, but have to used the syntax with all parameters:
AT+ECHO=1,6,30,8000,256 for instance.
• To use Echo Cancellation 6, the ECHO feature must be activated.
• Note that Echo Cancellation algorithms may not be available on some modems:
Modem
A
lgorithm 6 Support
A
lgorithm 3 Support
Q24 Plus (AMR) Yes No
Values: <mode>
0 Deactivate Echo
1 Activate Echo
When mode = 1 is choosen, AlgoId is mandatory.
<status>
0 Echo Deactivated
1 Echo Activated for Mic/Spk One
2 Echo Activated for Mic/Spk Two
3 Reset the product
Note: <Status> does not indicate the currently selected speaker. If Echo is activated, it indicates
the speaker for which Echo parameters are set. Echo can be activated on a non-selected speaker.
<AlgoId>
1 Echo cancellation 1
6 Echo cancellation 6: AEC algorithm
Note that Echo Cancellation algorithms may not be available on some modems. Refer to the
description above.
• Echo Cancellation 1 (4 parameters):
♦ <Volout> Specifies the maximum attenuation of the switch
0 31 db (default)
1 29 db
2 27 db
3 25 db
…
14 3 db
15 1 db
♦ <Step> Specifies the attenuation step between attenuation and no attenuation.
0 1 db
1 2 db
2 3 db
3 4 db (default)
♦ <PcmThRel> Specifies the relative threshold between max and min energy information.
The allowed range is [0 - 31]. Default = 10.
♦ <PcmThMax> Specifies threshold of max energy information.
The allowed range is [0 - 31]. Default = 7.
• Echo Cancellation 6 (12 parameters):
♦ <AlgoParam> High value leads to high echo attenuation but the full-duplex quality will be
less efficient.
The allowed range is [ 0 - 63 ]. (30 by default)
♦ <NoiseThres> indicates the noise threshold. Low value leads to high noise attenuation.
The threshold 32767 indicates no noise attenuation. The allowed range is [0 - 32767].
T
he default is
50. The values above 512 have no effect (noise reduction will be disabled)
♦ <NmbTaps> indicates the Number of Taps of the Adaptive Filter. The allowed range is [2 -
256].
The default is 256.
64 taps = short Echo
256 taps = long Echo