User's Manual

GE910 Hardware User Guide
GE910 Hardware User GuideGE910 Hardware User Guide
GE910 Hardware User Guide
1vv0300962 Rev.9-bis3 2013-05-20
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 63 of 87
Mod. 0805 2011-07 Rev.2
11.2.4. Electrical Characteristics
11.2.4.1. Input Lines
Microphone/Line-in path
Line Type Differential
Coupling capacitor ≥ 100nF
Differential input resistance 10kΩ
Levels
To have 0dBm0 @1KHz (*) Differential input voltage
AT#HFMICG=0 290mVrms
AT#HFMICG=1 (+6dB) 145mVrms
AT#HFMICG=2 (+12dB) 72mVrms
AT#HFMICG=3 (+18dB) 36mVrms
AT#HFMICG=4 (+24dB) 18mVrms
AT#HFMICG=5 (+30dB) 9mVrms
AT#HFMICG=6 (+36dB) 4.5mVrms
AT#HFMICG=7 (+42dB) 2.25mVrms
(*) 0 dBm0 in the network are -3.14 dBfs
TIP: The Electret microphone is internally amplified by a J-FET transistor, thus the sound is
carried out as saturation drain current; this means that the Norton equivalence has to be
considered. The signal is converted to voltage on the 2.2KOhm resistance, from there on
circuitry has to be routed in order to not pick up common mode noise; beware of the return
path (ground).