Fostex CR200 Service Manual page 5

1-2. Pregrooved track wobbling + ATIP
When manufacturing the CD-R disc, it has been ÒpregroovedÓ. This pregroove in the CD-R disc is not a perfect spiral but
is wobbled so that the CD-R disc can be recognized by a CD-R recorder even when it is completely blank.
It has many purposes. It not only helps keep the servo on an exact tracking of outgoing spiral but also the demodulated
wobbling frequency contains the time information in digital format (21.05 kHz = Ò0Ó, 23.05 kHz = Ò1Ó). These frequencies
have been selected so that the mean frequency is equal to Fs / 2 (= 22.05 kHz). Also the interleaved is the manufacturer's
measured default laser power level.
1-3. PCA + consequence
Each recorder has a tolerance in the laser power and the dye from different manufacturers varies. In order to optimize the
recorder / disc combination, there is a PCA (Power Calibration Area) included in the CD-R disk. This area consists of two
parts, the Count Area and Test Area. In the Test Area, test recordings are made, stepping through several power levels. After
playing back the recorded test signal, the optimum level is automatically determined. This value is memorized until the disk
tray is opened. The Count Area keeps the track on how many of the test areas have been used indicating where to start the
next test. The PCA is designed to accommodate for 100 tests. When the PCA is full, the default value written in the wobbled
groove is used instead.
Test Area
Partition
100 98
Fig. 3 Organization of PCA, PMA and Lead-In Area
CAUTION :
Every time the CD-R disc is inserted, one test is performed. Also if you leave the disc in the recorder at power off, a test will
be performed when powering on. This might lead to the situation that the PCA might be fully used up even if there is a
remaining space to record audio signal. The recordings made after the PCA is fully used up will not be optimal in performance.
0.6µm
(track width)
22.05 ± 1kHz = ~ 60µm
Fig. 2 Structure of Pregrooved Disc
PCA
98
4 3 2 1
Count Area
5 3 1
CR200
1.6µm
(track distance)
Lead In
PMA Area
5