<s>
The	O
PR-7820	O
is	O
the	O
only	O
player	O
ever	O
sold	O
to	O
either	O
the	O
industrial	O
or	O
consumer	O
market	O
that	O
was	O
entirely	O
designed	O
and	O
engineered	O
by	O
the	O
technicians	O
at	O
MCA	O
Disco-Vision	O
and	O
contained	O
all	O
of	O
their	O
preferred	O
design	O
approaches	O
,	O
such	O
as	O
playing	O
the	O
disc	O
with	O
the	O
laser	O
on	O
top	O
(	O
instead	O
of	O
underneath	O
)	O
and	O
moving	O
the	O
disc	O
radially	O
to	O
provide	O
tracking	B-Operating_System
instead	O
of	O
moving	O
the	O
laser	O
radially	O
.	O
</s>
<s>
An	O
external	O
computer	B-Application
interface	I-Application
box	O
was	O
also	O
made	O
available	O
at	O
the	O
same	O
time	O
which	O
contained	O
additional	O
memory	B-General_Concept
that	O
increased	O
the	O
total	O
size	O
of	O
a	O
disc-based	O
computer	B-Application
program	I-Application
the	O
PR-7820	O
could	O
store	O
and	O
execute	O
to	O
256k	O
.	O
</s>
<s>
The	O
PR-7820	O
was	O
the	O
first	O
LD	O
player	O
to	O
use	O
solid-state	O
tangential	O
tracking	B-Operating_System
instead	O
of	O
a	O
tangential	O
tracking	B-Operating_System
mirror	O
,	O
the	O
PR-7820	O
used	O
an	O
electronic	O
CCD	B-Algorithm
delay	O
line	O
to	O
provide	O
tangential	O
tracking	B-Operating_System
corrections	O
,	O
giving	O
the	O
player	O
superb	O
color	O
quality	O
.	O
</s>
<s>
Fully	O
functional	O
PR-7820s	O
are	O
not	O
easily	O
available	O
on	O
eBay	B-Application
and	O
are	O
nearly	O
impossible	O
to	O
find	O
in	O
fully	O
functional	O
condition	O
.	O
</s>
