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AC75 Hardware Interface Description
Strictly confidential / Preliminary
5.7.3 Characteristics of Audio Modes
The electrical characteristics of the voiceband part depend on the current audio mode set
with the AT^SNFS command. All values are noted for default gains e.g. all parameters of
AT^SNFI and AT^SNFO are left unchanged.
Table 31: Voiceband characteristics (typical)
Audio mode no.
1 (Default
AT^SNFS=
settings, not
adjustable)
Name
Default
Handset
Purpose
DSB with
Votronic
handset
Gain setting via AT
Fix
command. Defaults:
inBbcGain
5 (30dB)
outBbcGain
1 (-6dB)
Default audio
1
interface
Power supply VMIC
ON
Sidetone
Fix
Volume control
Fix
Echo control
Echo canceller
ON
Loss controller
3dB / 6dB
idle/full attenuation
Comfort noise
ON
generator
Non linear processor ON
MIC input signal for
0dBm0
18mV
-10dBm0
5.8mV
f=1024 Hz
EP output signal in
475mV
mV rms. @ 0dBm0,
1024 Hz, no load
(default gain) /
@ 3.14 dBm0
Sidetone gain at
21.9dB
default settings
NOTE: With regard to acoustic shock, the cellular application must be designed to avoid
sending false AT commands that might increase amplification, e.g. for a highly sensitive
earpiece. A protection circuit should be implemented in the cellular application.
9
Audio mode 5 and 6 are identical. AT^SAIC can be used to switch mode 5 to the second interface. Audio mode
6 is therefore kept mainly for compatibility to earlier Siemens GSM products.
10
In audio modes with an active loss controller a continuous sine signal is attenuated by the idle attenuation after
a few seconds. All input voltages are noted for the idle attenuation. If the idle attenuation is higher than 3 dB,
0dBm0 cannot be reached without clipping. In this case only the value for -10dBm0 is noted.
AC75_HD_V00.202
2
3
Basic
Headset
Handsfree
Siemens
Siemens
Car Kit
Headset
Portable
Adjustable
Adjustable
2 (12dB)
5 (30dB)
2 (-12dB)
1 (-6dB)
2
2
ON
ON
---
Adjustable
Adjustable
Adjustable
ON
ON
4dB / 50dB
9dB / 18dB
ON
ON
ON
ON
10
10
---
---
95mV
14mV
70mV
270mV
default @
default @
max volume
max volume
-∞ dB
10.0dB
Page 98 of 120
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4
5
User
Plain
Handset
Codec 1
DSB with
Direct access
individual
to speech
handset
coder
Adjustable
Adjustable
5 (30dB)
0 (0dB)
1 (-6dB)
0 (0dB)
1
1
ON
ON
Adjustable
Adjustable
Adjustable
Adjustable
ON
OFF
3dB / 6dB
OFF
ON
OFF
ON
OFF
18mV
400mV
5.8mV
126mV
475mV
1.47V
default @
max volume
Vpp = 6.2 V
21.9dB
-∞ dB
6
Plain
Codec 2
Direct access
to speech
coder
Adjustable
0 (0dB)
0 (0dB)
9
2
ON
Adjustable
Adjustable
OFF
OFF
OFF
OFF
400mV
126mV
1.47V
-∞ dB
27.04.2006
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