<s>
In	O
telecommunication	O
and	O
data	B-General_Concept
storage	I-General_Concept
,	O
Manchester	B-Protocol
code	I-Protocol
(	O
also	O
known	O
as	O
phase	B-Protocol
encoding	I-Protocol
,	O
or	O
PE	B-Protocol
)	O
is	O
a	O
line	B-Protocol
code	I-Protocol
in	O
which	O
the	O
encoding	O
of	O
each	O
data	O
bit	O
is	O
either	O
low	O
then	O
high	O
,	O
or	O
high	O
then	O
low	O
,	O
for	O
equal	O
time	O
.	O
</s>
<s>
Consequently	O
,	O
electrical	O
connections	O
using	O
a	O
Manchester	B-Protocol
code	I-Protocol
are	O
easily	O
galvanically	O
isolated	O
.	O
</s>
<s>
Manchester	B-Protocol
code	I-Protocol
derives	O
its	O
name	O
from	O
its	O
development	O
at	O
the	O
University	O
of	O
Manchester	O
,	O
where	O
the	O
coding	O
was	O
used	O
for	O
storing	O
data	O
on	O
the	O
magnetic	O
drums	O
of	O
the	O
Manchester	B-Device
Mark	I-Device
1	I-Device
computer	O
.	O
</s>
<s>
Manchester	B-Protocol
code	I-Protocol
was	O
widely	O
used	O
for	O
magnetic	B-Architecture
recording	I-Architecture
on	O
1600bpi	O
computer	O
tapes	O
before	O
the	O
introduction	O
of	O
6250bpi	O
tapes	O
which	O
used	O
the	O
more	O
efficient	O
group-coded	B-Device
recording	I-Device
.	O
</s>
<s>
Manchester	B-Protocol
code	I-Protocol
was	O
used	O
in	O
early	O
Ethernet	B-Protocol
physical	I-Protocol
layer	I-Protocol
standards	O
and	O
is	O
still	O
used	O
in	O
consumer	O
IR	O
protocols	O
,	O
RFID	B-Application
and	O
near-field	O
communication	O
.	O
</s>
<s>
Manchester	B-Protocol
coding	I-Protocol
is	O
a	O
special	O
case	O
of	O
binary	O
phase-shift	O
keying	O
(	O
BPSK	O
)	O
,	O
where	O
the	O
data	O
controls	O
the	O
phase	O
of	O
a	O
square	O
wave	O
carrier	O
whose	O
frequency	O
is	O
the	O
data	O
rate	O
.	O
</s>
<s>
Manchester	B-Protocol
code	I-Protocol
ensures	O
frequent	O
line	O
voltage	O
transitions	O
,	O
directly	O
proportional	O
to	O
the	O
clock	O
rate	O
;	O
this	O
helps	O
clock	O
recovery	O
.	O
</s>
<s>
Therefore	O
connections	O
may	O
be	O
inductively	O
or	O
capacitively	O
coupled	O
,	O
allowing	O
the	O
signal	O
to	O
be	O
conveyed	O
conveniently	O
by	O
galvanically	O
isolated	O
media	O
(	O
e.g.	O
,	O
Ethernet	O
)	O
using	O
a	O
network	B-Device
isolator	I-Device
—	O
a	O
simple	O
one-to-one	O
pulse	O
transformer	O
which	O
cannot	O
convey	O
a	O
DC	O
component	O
.	O
</s>
<s>
Manchester	B-Protocol
coding	I-Protocol
's	O
data	O
rate	O
is	O
only	O
half	O
that	O
of	O
a	O
non-coded	O
signal	O
,	O
which	O
limits	O
its	O
usefulness	O
to	O
systems	O
where	O
bandwidth	B-Algorithm
is	O
not	O
an	O
issue	O
,	O
such	O
as	O
a	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
(	O
LAN	B-General_Concept
)	O
.	O
</s>
<s>
Manchester	B-Protocol
encoding	I-Protocol
introduces	O
difficult	O
frequency-related	O
problems	O
that	O
make	O
it	O
unsuitable	O
for	O
use	O
at	O
higher	O
data	O
rates	O
.	O
</s>
<s>
There	O
are	O
more	O
complex	O
codes	O
,	O
such	O
as	O
8B/10B	B-Protocol
encoding	I-Protocol
,	O
that	O
use	O
less	O
bandwidth	B-Algorithm
to	O
achieve	O
the	O
same	O
data	O
rate	O
but	O
may	O
be	O
less	O
tolerant	O
of	O
frequency	O
errors	O
and	O
jitter	O
in	O
the	O
transmitter	O
and	O
receiver	O
reference	O
clocks	O
.	O
</s>
<s>
Manchester	B-Protocol
code	I-Protocol
always	O
has	O
a	O
transition	O
at	O
the	O
middle	O
of	O
each	O
bit	O
period	O
and	O
may	O
(	O
depending	O
on	O
the	O
information	O
to	O
be	O
transmitted	O
)	O
have	O
a	O
transition	O
at	O
the	O
start	O
of	O
the	O
period	O
also	O
.	O
</s>
<s>
The	O
second	O
convention	O
is	O
also	O
followed	O
by	O
numerous	O
authors	O
(	O
e.g.	O
,	O
William	O
Stallings	O
)	O
as	O
well	O
as	O
by	O
IEEE	B-Protocol
802.4	I-Protocol
(	O
token	B-Protocol
bus	I-Protocol
)	O
and	O
lower	O
speed	O
versions	O
of	O
IEEE	O
802.3	O
(	O
Ethernet	O
)	O
standards	O
.	O
</s>
<s>
This	O
ambiguity	O
can	O
be	O
overcome	O
by	O
using	O
differential	B-Protocol
Manchester	I-Protocol
encoding	I-Protocol
.	O
</s>
<s>
The	O
price	O
of	O
these	O
benefits	O
is	O
a	O
doubling	O
of	O
the	O
bandwidth	B-Algorithm
requirement	O
compared	O
to	O
simpler	O
NRZ	B-Protocol
coding	O
schemes	O
.	O
</s>
