User's Manual

WM_PRJ_Q2400_PTS_002 - 004
March 5, 2004
2.13 Audio interface
Two different microphone inputs and two different speaker outputs are supported.
The WISMO Quik Q24x6 sub-series also includes an echo cancellation feature which allows hands-
free function.
In some case, ESD protection must be added on the audio interface lines.
2.13.1 Microphone inputs
The MIC2 inputs already include the biasing for an electret microphone allowing an easy connection
to a handset.
The MIC1 inputs do not include an internal bias. MIC1/SPK1 is then appropriate for a hands-free
system or a handset with biasing external to the module.
2.13.1.1 Common microphone inputs characteristics
The connection can be either differential or single-ended but using a differential connection in order
to reject common mode noise and TDMA noise is strongly recommended. When using a single-
ended connection, be sure to have a very good ground plane, a very good filtering as well as
shielding in order to avoid any disturbance on the audio path.
Internal audio filter characteristics
Frequency Gain
0-150 Hz < -22 dB
150-180 Hz < -11 dB
180-200 Hz < -3 dB
200-3700 Hz 0 dB
>4000 Hz < -60 dB
The gain of MIC inputs is internally adjusted and can be tuned from 30 dB to 51 dB using an AT
command (refer to AT commands documentation [3]).
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