<s>
Embedded	B-Device
servo	I-Device
or	O
wedge	O
servo	O
is	O
a	O
type	O
of	O
servo	O
configuration	O
used	O
on	O
hard	B-Device
disks	I-Device
.	O
</s>
<s>
Embedded	B-Device
servo	I-Device
systems	O
embed	O
the	O
feedback	O
signals	O
for	O
the	O
read/write	O
head	O
positioner	O
(	O
usually	O
a	O
voice	B-Device
coil	I-Device
motor	O
)	O
inside	O
gaps	O
(	O
wedges	O
)	O
in	O
the	O
data	O
tracks	O
of	O
the	O
disk	O
.	O
</s>
<s>
Embedded	B-Device
servo	I-Device
was	O
originally	O
developed	O
in	O
the	O
1970s	O
,	O
and	O
started	O
to	O
appear	O
on	O
mass-market	O
hard	B-Device
drives	I-Device
for	O
personal	B-Device
computers	I-Device
in	O
the	O
late	O
1980s	O
.	O
</s>
<s>
As	O
with	O
dedicated-servo	O
drives	O
,	O
the	O
control	O
signals	O
are	O
written	O
at	O
the	O
factory	O
using	O
a	O
special	O
device	O
called	O
a	O
servowriter	B-Device
,	O
and	O
cannot	O
usually	O
be	O
regenerated	O
in	O
the	O
field	O
.	O
</s>
