User's Manual

GE/GC864-QUAD V2 and GE864-GPS Hardware User Guide
1vv0300915 Rev.2 – 2011-06-15
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights
Reserved. Page 66 of 97
10. Audio Section Overview
The first 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 internal 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 different definitions were introduced, with
the following meaning:
• internal audio transducers  HS/MT (from 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 drive the
speaker, he needs to adopt the Aduio2 Section ( HF ) .
Otherwise 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 GE864-QUAD V2 Telit Modules
maintains the same architecture.
For more information and suggestions refer to Telit document:
• Audio settings application note , 80000NT10007a
10.1. Selection mode
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 .
Moreover the Sidetone functionality could be implemented by
the amplifier fitted between the transmit path and the receive
path, enabled at request in both modes.