Pioneer CDX-M12 Service Manual page 53

(2) Focus OK circuit
The FOK circuit compares the upper envelope of an RF
signal with the value set by the microcomputer and out-
puts a result of such comparison at the FOK terminal.
("H" is outputted, with [RF signal's upper envelope] > [set value].)
o| ah FOK T Lo| a
Focus OFF
Fig. 26
(3) EFM comparator
The EFM comparator is to digitize an RF signal.
Since its error rate increases under the influence of an
asymmetry generated, the EFM output signal is made
to pass through a low-pass filter by making use of the
fact that a bit is generated at a probability of 50 %. And
the signal so filtrated is taken for a comparison level.
The present system has a low-pass filter cut off fc = 3.3
(Hz) for C604 and R606 and fc = 1.6 (kHz) for C605 and
R607.
selecting signal
C603
330p
RF —4
R606 R607 i
220k 10k
1
1
1
1
t
!
!
1
1
IC 601
UPD6374AGH
EFM comparator
Fig. 27
69