GE/GC864-QUAD V2 and GE864-GPS Hardware User Guide
1vv0300915 Rev.5 – 2011-10-03
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved.
Page 61 of 94
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
H
and
S
et
or
M
icro
T
elephone
)
external audio transducers
HF
(from
H
ands
F
ree )
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.
