Sony Model PMC-MD55 - Manual (Page 74)

Additional Information 74 GB
Disc variation
MDs come in two types: pre-mastered
(pre-recorded) and recordable (blank).
Pre-mastered MDs cannot be recorded
on or over like cassette tapes. To record,
you must use a “recordable MD.”
Pre-mastered MDs
Pre-mastered MDs are recorded and
played like regular CDs. A laser beam
focus on the pits on the surface of the
MD and reflects the information back to
the lens in the recorder. The recorder
then decodes the signals and plays them
back as music.
Recordable MDs
Recordable MDs, which use magneto-
optical (MO) technology, can be
recorded again and again. The laser
inside the recorder applies heat to the
MD, demagnetizing the magnetic layer
of the MD. The recorder then applies a
magnetic field to the layer. This
magnetic field corresponds exactly to
the audio signals generated by the
connected source. (The north and south
polarities equate to digital “1” and “0.”)
The demagnetised MD adopts the
polarity of the magnetic field, resulting
in a recorded MD.
Getting to know the MD
Structure
The 2.5-inch MiniDisc (MD) is compact
and easy to handle requiring less care as
it is encased in a plastic cartridge that
looks like a 3.5-inch diskette (see
illustrations below).
Parts making up a MiniDisc
Plastic cartridge
Disc
Shutter