Service manual CP 385 / CP785
In case of NICAM - mode, the phase samples are decoded according the DQPSK - coding scheme. The
output of this block contains the original NICAM bitstream.
DSP section
All audio baseband functions are performed by digital signal processing (DSP). The DSP section
controls the source and output selection, and the signals processing.
Sound Mode switching
In case of NICAM transmission, the controlling software read the bit error rate and the operation mode
from the NICAM Decoder. When the set is in ?Auto detection? mode ( default mode after ATSS ) the
controlling software set automatically the sound mode ( NICAM mono, NICAM Dual 1 or NICAM
Dual 2 ) depending on the transmitted mode.
In case of 2 Carrier FM transmission, the controlling software read the transmission mode and the
signal quality level from the Stereo Detection Register. When the set is in ?Auto detection? mode the
controlling software set automatically the sound mode ( mono, Stereo, Dual 1, Dual 2 ) depending on
the transmitted mode.
In ?Auto detection? mode the controlling software evaluate the signal quality and automatically switch
to the analogy sound carrier 1, if the transmission quality is too poor. To avoid unwanted automatic
switching the threshold levels mono to stereo and stereo to mono is different.
In ?forced mono ? mode ( Red OSD in recall section ), the controlling software configure the
MSP3415D to demodulate only the analogue (FM or AM) sound carrier 1, no matter the signal quality.
The sound mode ? forced ? or ? Autodetect? is stored for each programme.
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ACEC
