MC75i Hardware Interface Description
3.15 Audio Interfaces
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MC75i_HD_v01.100a
Page 59 of 122
2009-08-13
Confidential / Released
3.15
Audio Interfaces
MC75i comprises three audio interfaces available on the board-to-board connector:
•
Two analog audio interfaces.
•
Serial digital audio interface (DAI) designed for PCM (Pulse Code Modulation).
This means you can connect up to three different audio devices, although only one interface
can be operated at a time. Using the AT^SAIC command you can easily switch back and forth.
Figure 23:
Audio block diagram
To suit different types of accessories the audio interfaces can be configured for different audio
modes via the AT^SNFS command. The electrical characteristics of the voiceband part vary
with the audio mode. For example, sending and receiving amplification, sidetone paths, noise
suppression etc. depend on the selected mode and can be altered with AT commands (except
for mode 1).
Both analog audio interfaces can be used to connect headsets with microphones or speaker-
phones. Headsets can be operated in audio mode 3, speakerphones in audio mode 2. Audio
mode 5 can be used for direct access to the speech coder without signal pre or post processing.
When shipped from factory, all audio parameters of MC75i 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 Cinterion Wireless Modules 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.
