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GE864 Hardware User Guide
1vv0300694 Rev.10 - 10/06/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 41 of 69
9.1.2 Input Lines Characteristics
“MIC_MT” 1st differential microphone path
Line Coupling AC*
Line Type Balanced
Coupling capacitor ≥ 100nF
Differential input resistance 50kΩ
Differential input voltage ≤ 1,03V
pp
(365mV
rms
)
Microphone nominal sensitivity -45 dBV
rms
/Pa
Analog gain suggested + 20dB
Echo canceller type Handset
“MIC_HF” 2nd differential microphone path
Line Coupling AC*
Line Type Balanced
Coupling capacitor ≥ 100nF
Differential input resistance 50kΩ
Differential input voltage ≤ 65mV
pp
(23mV
rms
)
Microphone nominal sensitivity -45 dBV
rms
/Pa
Analog gain suggested +10dB
Echo canceller type Car kit hands-free
(*) WARNING: AC means that the signals from microphone has to be connected to input lines of the
module by a CAPACITOR, which value must be ≥ 100nF. Not respecting this constraint, the input stage
will be damaged.