<s>
Optical	B-Device
discs	I-Device
,	O
with	O
the	O
exception	O
of	O
DVD-RAM	O
,	O
have	O
their	O
data	O
encoded	O
on	O
a	O
single	O
spiral	O
,	O
or	O
a	O
groove	O
,	O
which	O
covers	O
the	O
surface	O
of	O
the	O
disc	O
.	O
</s>
<s>
The	O
period	O
of	O
this	O
sine	O
curve	O
corresponds	O
to	O
the	O
wobble	B-Device
frequency	I-Device
.	O
</s>
<s>
The	O
wobble	B-Device
frequency	I-Device
is	O
commonly	O
used	O
as	O
a	O
synchronization	O
source	O
to	O
achieve	O
constant	B-Device
linear	I-Device
velocity	I-Device
while	O
writing	O
a	O
disc	O
,	O
but	O
has	O
other	O
uses	O
as	O
well	O
depending	O
on	O
the	O
type	O
of	O
disc	O
.	O
</s>
<s>
CD-R	O
and	O
CD-RW	O
discs	O
use	O
a	O
frequency	B-Application
modulated	I-Application
wobble	O
of	O
22.05kHz	O
to	O
encode	O
information	O
,	O
such	O
as	O
the	O
Absolute	B-Device
Time	I-Device
in	I-Device
Pregroove	I-Device
(	O
ATIP	O
)	O
,	O
into	O
the	O
groove	O
.	O
</s>
<s>
DVD-R	O
and	O
DVD-RW	O
have	O
a	O
constant	O
wobble	B-Device
frequency	I-Device
of	O
140.6kHz	O
relying	O
on	O
data	O
'	O
pits	O
 '	O
beside	O
the	O
groove	O
to	O
convey	O
information	O
(	O
Land	O
pre-pit	O
)	O
.	O
</s>
<s>
DVD+R	O
and	O
DVD+RW	O
have	O
a	O
constant	O
wobble	B-Device
frequency	I-Device
of	O
817.4kHz	O
,	O
but	O
encodes	O
its	O
addressing	O
information	O
by	O
periodically	O
inverting	O
the	O
phase	O
of	O
the	O
wobble	O
signal	O
(	O
bi-phase	O
modulation	O
)	O
to	O
encode	O
an	O
exact	O
address	O
of	O
the	O
location	O
on	O
the	O
spiral	O
track	O
(	O
Address	O
in	O
Pregroove	O
)	O
.	O
</s>
<s>
BD-R	B-Operating_System
and	O
BD-RE	B-Operating_System
discs	O
utilise	O
Address	O
in	O
Pregroove	O
.	O
</s>
<s>
HD	B-Operating_System
DVD-R	I-Operating_System
and	O
HD	B-Operating_System
DVD-RW	I-Operating_System
use	O
the	O
land	O
pre-pit	O
system	O
of	O
the	O
DVD-R(W )	O
.	O
</s>
