User's Manual

GE910 Hardware User Guide
1vv0300962 Rev.12 2013-10-22
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved
page 56 of 83
Mod. 0805 2011-07 Rev.2
11.2.2. LINE-IN connection
100n
100
33pF 33pF
100n
100
33pF 33pF
MIC+
MIC-
GND
LINE_IN+1
Remote_GND
TELIT MODULE
-
+
INPUTADC
100n
100
33pF 33pF
100n
100
33pF 33pF
MIC+
MIC-
GND
TELIT MODULE
-
+
INPUTADC
LINE_IN+
LINE_IN-
If the audio source is not a mike but a different device, the following connections can be done.
Place 100nF capacitor in series with both inputs, so the DC current is blocked.
Place the 33pF-100Ohm-33pF -RF filter, in order to prevent some EMI field to get into the
high impedance high gain MIC inputs.
Since the input is differential, the common mode voltage noise between the two (different)
grounds is rejected, provided that both MIC+ & MIC- are connected directly onto the source.