User's Manual

GE864- QUAD Har dwar e User Guide
1vv0300872 Rev.1 2010-04-02
- All Rights Reserved. Page 46 of 77
10. Audio Section Overview
The Baseband chip was developed for the cellular phones, which needed two
separated amplifiers both in RX and in TX section.
A couple of amplifiers had to be used with inter nal audio transducers while the other
couple of amplifiers had to be used with external audio transducers.
To distinguish the schematic signals and the Software identifiers, two differ ent
definitions were intr oduced, with the following meaning:
internal audio transducers  HS/MT (fr om HandSet or MicroTelephone )
external audio transducers  HF (from HandsFree )
Actually the acronyms have not the original importance.
In other words this distinction is not necessary, being the performances between the
two blocks like the same.
Only if the customer needs higher output power to the speaker , he has a constr aint.
Other wise the choice could be done in order to overcome the PCB design difficulties.
For these reasons we have not changed the HS and HF acronyms, keeping them in
the Software and on the schematics.
The Base Band Chip of the GE864Telit Module maintains the same architecture.
For more information refer to Telit document :
“
80000NT10007a Audio Settings Application Note “.
1.1 Sel ection m ode
Only one block can be active at a time , and the activation of the requested audio
path is done via hardware by
AXE line or via software by AT# CAP command .
Mor eover the Sidetone functionality could be implemented by the amplifier fitted
between the transmit path and the receive path, enabled at request in both modes.