Technical data

WMO2 G900 / G1800 / G1900
WCOM/GSM/WMO2/WMO2ATDOC Friday 21 May 1999
WAVECOM confidential © 34
4.2.12 Echo Cancelation +ECHO
Command syntax: AT+ECHO= <mode>, [<Taps>,<ConvTh>,<DbtS>, <FarS>,
<EcDelay> ]
This specific command is used to activate, deactivate or configure
the Echo Cancelation function.
Defined Values
<mode>:
0: Deactivate Echo
1: Activate Echo
2: Configure the echo cancelation (automatically stored in E2P)
<Taps>: Number of taps of the adaptive filter. This value is directly
related to the length of the longest echo path (240 words = 30 ms echo
path delay). Values from 1 to 192, default is 160
<ConvTh>: Threshold for convergence parameter. This specifies the level of
energy computed on <EcDelay> samples needed to assume algorithm
convergence. A low value provides a high convergence and a high value a
high stability. Values from 0 to 45, default is 12.
<DbtS>: Double talk sensitivity. This reflect the ratio between received
and sent energy to assume double talk occured. A low value provides a
high sensibility and a high value a low one. Values from 0 to 10, default is
5.
<FarS>: Far end speaker detection - algorithm adaptation. This is related
to then energy level needed on the receive path to allow filter taps
adaptation. If <FarS> = 0 the algorithm will always adjust the filter. Values
from 0 to 1000, default is 512.
<EcDelay>: Number of samples used to compute energy for algorithm
convergence evaluation. Values from 1 to 30, default is 10
4.2.13 SideTone modification +SIDET
Command syntax: AT+SIDET=<val1>,<val2>
This specific command is used to get an echo of the voice in the speaker
(to hear what is said in the speaker).
<val2> Level <val1> presence
0 0 db 0 SideTone is disabled
1 - 6 db 1 SideTone is enabled
2 -12 db
3 -18 db
Application to GSM AT+SIDET=1,0
GSM to application OK Command valid
Application to GSM AT+SIDET? Current value
GSM to application +SIDET: 1,0
OK
Command valid