Multi-Tech Systems GPRS (MTMMC-G) User Manual

Chapter 5 – Call Control Commands 

Multi-Tech Systems, Inc. Wireless GSM/GPRS AT Commands (Document Number S000293I) 

27 

 

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: 

Q24 Plus (AMR) 

Yes 

No 

 
Values: <mode> 

Deactivate Echo 

Activate Echo  

 

 

When mode = 1 is choosen, 

AlgoId is mandatory. 

 

 

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.  

 

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) 

29 db 

27 db 

25 db 

… 
14 

3 db 

1 db 

♦ 

<Step>   Specifies the attenuation step between attenuation and no attenuation. 

1 db 

2 db 

3 db 

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]. 

The 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