MC45 Hardware Interface Description
P R E L I M I N A R Y
MC45_HD_01_V00.02a Page 50 of 90 12.08.2002
When shipped from factory, all audio parameters of MC45 are set to interface 1 and audio
mode 1. This is the default configuration optimized for the Votronic HH-SI-30.3/V1.1/0
handset and used for type approving the Siemens reference configuration. Audio mode 1
has fix parameters which cannot be modified. To adjust the settings of the Votronic handset
simply change to another audio mode.
3.6.1 Microphone circuit
Interface 1
This interface has no microphone supply circuit and therefore, has an impedance of 50 k
W.
When connecting a microphone or another signal source to interface 1 you are required to
add two 100 nF capacitors, one to each line.
Interface 2
This interface comes with a microphone supply circuit and can be used to feed an active
microphone. If you do not use it or if you want to connect another type of signal source, for
example, an op amp or a dynamic microphone, it needs to be decoupled with capacitors.
Figure 17 shows the microphone inputs at both analog interfaces of MC45.
2.65 V
to ADC
Power down
MICP1
MICN1
MICP2
MICN2
1 k" 1 k"
1 k" 1 k"
10
F
Ri=50k"
Figure 17: Schematic of microphone inputs
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