MC55i Terminal Hardware Interface Description
3.7 Audio Interface
32
MC55i_Terminal_HD_v01.201a
Page 27 of 47
2010-04-16
Confidential / Released
3.7.1
Supported Audio Modes
The audio interface can be configured by AT commands. Refer to
for details.
The electrical characteristics of the voiceband part vary with the audio mode. Specifications are
listed in
. To suit several types of audio equipment, three audio modes given by default
can be selected by the AT command AT^SNFS.
Regarding audio performance, compliance with the TS 51010-1 specification and GCF recom-
mendations has been certified for the parameters provided by audio mode 1 and audio
interface 1. The settings are optimized for the reference handset (type Votronic) connected to
the MC55i Terminal. To ensure that the reference parameters are always within the limits de-
manded by the standards they cannot be changed by AT command. Furthermore, the refer-
ence parameters are set as factory default.
In audio mode 4 and 5, the gain in the microphone, earpiece and the sidetone path can be ad-
justed from the cellular device application by using further AT commands.
Please note that the 2
nd
audio interface of the MC55i module is not connected in the MC55i
Terminal. Audio modes 2, 3 and 6 can be selected by setting AT^SAIC=2,1,1, for further details
refer to
.
Table 11:
Audio modes
Audio mode number: AT^SNFS= 1 (Default settings,
not adjustable)
4
5
Audio mode name
Default Handset
User Handset
Plain Codec 1
Purpose
Recommended hand-
set (see
User provided
handset
Direct access to
speech coder
Gain programmable via AT com-
mand
NO
YES
YES
Sidetone
YES
YES
YES
Volume control
NO
YES
YES
Echo control (send)
Cancellation
Cancellation
NO
MIC input signal for 0dBm0
@ 1024 Hz
(at default gain settings)
18mV
18mV
315 mV
Earpiece output signal in mV eff. @
0dBm0, 1024 Hz, no load (at
default gain settings);
@ 3.14 dBm0
620mV
620mV
default @ max vol-
ume
880 mV
3.7 Vpp
Sidetone gain (at default settings)
21.5dB
21.5dB
-
dB
