Function Reference
NICAM Sound
5
5-47
TEST 1 is used for checking the 4QPSK demodulator. By this method a triggerable sig-
nal at the data output of the NICAM demodulator circuit TDA 8732 can be displayed on
the screen of an oscilloscope. The subsequent circuit SAA 7280 (Terrestrial Digital
Sound Decoder) in this case sends an error message (error flag) and thus indicates faulty
NICAM data.
Similar circuit design is also used by other manufacturers, for example the demodulator
circuit from Toshiba TA 8662N or the decoder circuit CF 70123 from Texas Instrument.
TEST 2 checks NICAM decoders, for example, it sends a continuous 32 kHz square
wave signal at the I
2
S bus output of the SAA 7280, which can easily be displayed on the
screen of an oscilloscope.
TEST 3 generates an unmodulated NICAM sound carrier signal that is suited for adjust-
ment and level measurements.
Figure 5-32. NICAM Receiver for TV Sets (Philips)
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