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XD-980MD (En)
74
Preparation sectionBasic sectionApplication sectionKnowledge sections
In case of difficulty
The Mini Disc system has the features as summarized in the following.
1 Like CD (Compact Disc), playback can be started from any position. (Random access)
2 It uses a disc with a diameter of 64 mm that is accommodated in a cartridge.
3 Two types of discs can be used.
4 Up to 74 minutes of recording or playback is possible using high-efficiency coding technology.
5 Countermeasure against vibration is taken using semiconductor memory chip.
Recordable Mini Disc
There are two types of Mini Disc, the one designed exclusively for
playback and the other which is both recordable and playable.
This MD is a magneto-optical disc which can be recorded by magnetic
field modulation. To record signals, laser light is irradiated from the
bottom side of the magneto-optical disc and magnetic field is applied
from the upper side of it.
Sound-skip prevention memory
During playback, this unit always stores signals in memory temporarily
to prevent sound from being skipped in case of vibration. As a result,
even when the data from the optical pickup is interrupted due to
vibration, etc., the music will not be interrupted because the memory
holds the data for several seconds.
During normal
playback
MD system
Two Mini Disc types
Playback-only Mini Disc
This type of MD can be used only for playback, and is used by the
commercially-available music MD software packages. The playback-only
MD is an optical disc like the Compact Disc (CD). The signals are recorded
as the presence or absence of small pits and read out by an optical, non-
contact pickup.
High-efficiency coding technology “ATRAC”
The Mini Disc has only a half the size of the Compact Disc but provides
the same recording time. This is made possible by ATRAC*, a newly
developed high-efficiency coding technology.
* ATRAC: Adaptive TRansform Acoustic Coding
The ATRAC compresses the music data to about 1/5 the amount of data
which would be obtained with conventional technology, by cutting off
the sound components which do not pose problem in audition even
when they are not present. This has made it possible to record or play up
to 74 minutes.
Digital memory
Reproduced
sound
The sound data for
several seconds is al-
ways stored during
playback.
Sound does not af-
fect the sensitivity
of ears
Small sound near
large sound
A small sound is not
audible to human ears
if it is produced at the
same time as a large
sound. (Masking ef-
fect)
Sensitivity of ears
Lowest and highest
frequencies are not
audible unless the
sound has a certain
level of volume.
Lowest fre-
quencies
Highest fre-
quencies
Mini Disc
Several sec. of data
In case of vibration
Even when the read-
out from disc is inter-
rupted momentarily
due to vibration or
shock, the repro-
duced sound from the
memory will not be
interrupted.
Reproduced
sound
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