User's Manual

Page 19 of 187
TECHNICAL MANUAL
Telit GM862 PCS
Tri Band GPRS Data Terminal System Rev.1
1.14 Audio levels specifications
The audio of the Telit GM862-PCS, module is organised into two main paths:
- internal path (called also MT)
- external path (called also HF)
These two paths are meant respectively for handset and headset/handsfree use.
The Telit GM862-PCS module has a built in echo canceller and a noise suppressor, tuned separately
for the two audio paths; for the internal path the echo canceller parameters are suited to cancel the
echo generated by a handset, while for the external audio path they are suited for a handsfree use.
For more information on the audio refer to the Hardware User Guide.
The following table reports all the audio level specifications.
Microphone characteristics
Internal audio mic. input External audio mic. input
Line coupling AC ( 100nF cond.) AC ( 100nF cond.)
Line type Balanced Balanced
Differential input resistance
25kΩ 25kΩ
Line nominal sensitivity 50mV
rms
3mV
rms
Max input voltage 360mV
rms
22mV
rms
Microphone nominal sensitivity
- Analog Gain suggested
-45dB
Vrms/Pa
/ +24dB -45dB
Vrms/Pa
/ +10dB
Echo canceller type Handset Car kit hands free
Speaker characteristics
Internal audio ear. output External audio ear. output
Line coupling DC DC
Line type Bridged Bridged
Speaker impedance
≥ 16Ω ± 5% @ 1kHz ≥ 16Ω ± 5% @ 1kHz
Minimun load impedance
15Ω 15Ω
Signal bandwidth 150-8000 Hz @ -3dB 150-8000 Hz @ -3dB
Maximum output 1700mV
rms
850mV
rms
Maximum power output 30mW 7.5mW
Volume level steps (SW) -2dB -2dB
Number of volume steps (SW) 10 10