<s>
Differential	O
Manchester	B-Protocol
encoding	I-Protocol
(	O
DM	O
)	O
is	O
a	O
line	B-Protocol
code	I-Protocol
in	O
digital	B-Protocol
frequency	I-Protocol
modulation	I-Protocol
in	O
which	O
data	O
and	O
clock	O
signals	O
are	O
combined	O
to	O
form	O
a	O
single	O
two-level	O
self-synchronizing	O
data	B-General_Concept
stream	I-General_Concept
.	O
</s>
<s>
In	O
various	O
specific	O
applications	O
,	O
this	O
method	O
is	O
also	O
called	O
by	O
various	O
other	O
names	O
,	O
including	O
biphase	B-Protocol
mark	I-Protocol
code	I-Protocol
(	O
CC	O
)	O
,	O
F2F	O
(	O
frequency/double	O
frequency	O
)	O
,	O
Aiken	O
biphase	O
,	O
and	O
conditioned	O
diphase	O
.	O
</s>
<s>
Differential	O
Manchester	B-Protocol
encoding	I-Protocol
is	O
a	O
differential	O
encoding	O
technology	O
,	O
using	O
the	O
presence	O
or	O
absence	O
of	O
transitions	O
to	O
indicate	O
logical	O
value	O
.	O
</s>
<s>
An	O
improvement	O
to	O
Manchester	B-Protocol
coding	I-Protocol
which	O
is	O
a	O
special	O
case	O
of	O
binary	O
phase-shift	O
keying	O
,	O
it	O
is	O
not	O
necessary	O
to	O
know	O
the	O
initial	O
polarity	O
of	O
the	O
transmitted	O
message	O
signal	O
,	O
because	O
the	O
information	O
is	O
not	O
represented	O
by	O
the	O
absolute	O
voltage	O
levels	O
but	O
by	O
their	O
transitions	O
.	O
</s>
<s>
Differential	O
Manchester	B-Protocol
encoding	I-Protocol
has	O
the	O
following	O
advantages	O
:	O
</s>
<s>
Unlike	O
with	O
Manchester	B-Protocol
encoding	I-Protocol
,	O
only	O
the	O
presence	O
of	O
a	O
transition	O
is	O
important	O
,	O
not	O
the	O
polarity	O
.	O
</s>
<s>
Other	O
line	B-Protocol
codes	I-Protocol
with	O
this	O
property	O
include	O
NRZI	O
,	O
bipolar	B-Protocol
encoding	I-Protocol
,	O
coded	B-Protocol
mark	I-Protocol
inversion	I-Protocol
,	O
and	O
MLT-3	B-Protocol
encoding	I-Protocol
.	O
</s>
<s>
These	O
positive	O
features	O
are	O
achieved	O
at	O
the	O
expense	O
of	O
doubling	O
the	O
clock	O
frequency	O
of	O
the	O
encoded	O
data	B-General_Concept
stream	I-General_Concept
.	O
</s>
<s>
Differential	O
Manchester	B-Protocol
encoding	I-Protocol
is	O
specified	O
in	O
the	O
IEEE	B-Device
802.5	I-Device
standard	O
for	O
Token	B-Device
Ring	I-Device
local	O
area	O
networks	O
,	O
and	O
is	O
used	O
for	O
many	O
other	O
applications	O
,	O
including	O
magnetic	O
and	O
optical	O
storage	O
.	O
</s>
<s>
As	O
Biphase	B-Protocol
Mark	I-Protocol
Code	I-Protocol
(	O
BMC	O
)	O
,	O
it	O
is	O
used	O
in	O
AES3	O
,	O
S/PDIF	O
,	O
SMPTE	O
time	O
code	O
,	O
USB	O
PD	O
,	O
xDSL	O
and	O
DALI	O
.	O
</s>
<s>
Differential	O
Manchester	B-Protocol
encoding	I-Protocol
is	O
also	O
the	O
original	O
modulation	O
method	O
used	O
for	O
single-density	O
floppy	B-Device
disks	I-Device
,	O
followed	O
by	O
double-density	O
modified	B-Protocol
frequency	I-Protocol
modulation	I-Protocol
(	O
MFM	B-Protocol
)	O
.	O
</s>
