Philips DVDR985 Technical Training Manual page 5

Frequency information, HF, is demodulated and
stored in RAM. When the RAM is half full, the
data is fed out to the Digital to Analog
Converters. The speed of the rotating disc is
servo controlled to keep the RAM half full. The
analog signals are amplified and sent to the out-
put connectors.
Record Once Technology
Disc Mechanical Layout
From an external point of view, a DVD is the
same as the CD. Recordable media creates the
need for three physical layouts. There are three
possible states of a disc: a blank disc, a partially
recorded disc, and a full or finalized disc. The
difference is in the way the Information Area is
divided. The Information Area of a blank disc
extends from 22.35 mm centered on the disc to
59 mm centered on the disc. Refer to Figure 6.
Figure 6 – A Partially Recorded Disc.
Figure 7 – Fully Recorded or Finalized Disc
A partially recorded disc's Information Area has
four sections: a PCA/RMA area, a Lead In Area,
a Recorded Program Area, and a Recordable
Program Area. See Figure 6 for the dimensions.
The PCA Area is the Power Calibration Area,
PCA. The RMA Area is the Recording
Management Area.
A fully recorded or finalized disc's Information
Area has three sections: A lead in Area, the
Program Area, and the Lead Out Area. See
Figure 7 for the dimensions.
The disc's recordable layer contains major differ-
ences from that of a stamped disc. The blank
disc has a Pre-groove stamped into the record-
able layer of the disc. This is polycarbonant for
DVD+Rs and organic dye material for
DVD+RWs. This spiral Pre-groove is for the
Servo circuit to provide a mechanical reference
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