User's Manual

Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 39 of 69
• The amplifier shall have a mute control to be used while not in conversation. This results in two
benefits: eliminating the background noise when not in conversation and saving power.
• The power to the amplifier should be decoupled as much as possible from the GM862-QUAD
power supply, by either keeping separate wires and placing bypass capacitors of adequate value
close to the amplifier power input pins.
• The biasing voltage of the amplifier shall be stabilised with a low ESR (e.g. a tantalum)
capacitor of adequate value.
NOTE: The GM862-QUAD audio path connected to the car kit hands free amplifier MUST be the
external one (EAR_HF), otherwise the echo cancellation will not be done due to the difference in the
echo canceller characteristics of the GM862-QUAD internal audio path from the external audio path.
An example of car kit amplifier schematic can be: