TC65 Terminal Hardware Interface Description
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TC65 Terminal_HD_V02.000b
Page 32 of 65
2007-02-19
3.7.2 Speech
Processing
The speech samples from the ADC are handled by the DSP of the baseband controller to
calculate e.g. amplifications, sidetone, echo cancellation or noise suppression depending on
the configuration of the active audio mode. These processed samples are passed to the
speech encoder. Received samples from the speech decoder are passed to the DAC after
post processing (frequency response correction, adding sidetone etc.).
Full rate, half rate, enhanced full rate, adaptive multi rate (AMR), speech and channel
encoding including voice activity detection (VAD) and discontinuous transmission (DTX) and
digital GMSK modulation are also performed on the GSM baseband processor.
Note: With regard to acoustic shock, the cellular application must be designed to avoid
sending false AT commands that might increase the amplification, e.g. for a high sensitive
earpiece.
