Telit EZ10-GPRS/-PCS
Product Description
80269ST10014a, Rev. 3 – 26/09/05
Reproduction forbidden without written authorization by Telit Communications S.p.A.
Page 19 of 74
All Rights reserved – Right of modification reserved
2.5.5 Audio Interface Specification
The audio input “MIC” and output “EAR” of the Telit EZ10 module are configured for
headset/hands-free use, referenced in the related GM862 module descriptions as “HF” audio path.
The Telit EZ10 module has a built in echo canceller and a noise suppressor tuned for a hands-free
use. See the GM862 HW User Guide for examples of microphone bias circuits and amplifiers as
well as of audio output amplifiers.
All audio input / output lines have a 100 pF bypass capacitor (v.5 and onwards) to ground and are
connected to the related pins of the GM862 module over a 100 Ohms series resistor and 1uF
series capacitor.
2.5.5.1 Microphone input characteristics
External audio MIC input
Line coupling
AC (1uF)
Line type
Balanced
Differential input resistance
25k
Ω
Line nominal sensitivity
3mV
rms
Max input voltage
22mV
rms
Microphone nominal
sensitivity - Analog Gain
suggested
-45dB
Vrms/Pa
/ +10dB
Echo canceller type
Car kit hands free
No bias voltage is provided on the MIC input. In case of need, external circuits have to be added,
which could be supplied from the VMOD output.
2.5.5.2 Speaker output characteristics
External audio EAR output
Line coupling
AC (1uF)
Line type
Bridged, unbalanced use
Speaker impedance
≥
16
Ω
±
5% @ 1kHz
Minimum load impedance
15
Ω
Signal bandwidth
150-8000 Hz @ -3dB
Maximum output
850mV
rms
Maximum power output
7.5mW
Volume level steps (SW)
-2dB
Number of volume steps (SW) 10
