<s>
In	O
telecommunication	O
,	O
a	O
longitudinal	B-Error_Name
redundancy	I-Error_Name
check	I-Error_Name
(	O
LRC	O
)	O
,	O
or	O
horizontal	B-Error_Name
redundancy	I-Error_Name
check	I-Error_Name
,	O
is	O
a	O
form	O
of	O
redundancy	O
check	O
that	O
is	O
applied	O
independently	O
to	O
each	O
of	O
a	O
parallel	O
group	O
of	O
bit	O
streams	O
.	O
</s>
<s>
The	O
term	O
usually	O
applies	O
to	O
a	O
single	O
parity	B-Error_Name
bit	I-Error_Name
per	O
bit	O
stream	O
,	O
calculated	O
independently	O
of	O
all	O
the	O
other	O
bit	O
streams	O
(	O
BIP-8	B-Protocol
)	O
,	O
although	O
it	O
could	O
also	O
be	O
used	O
to	O
refer	O
to	O
a	O
larger	O
Hamming	B-Error_Name
code	I-Error_Name
.	O
</s>
<s>
This	O
"	O
extra	O
"	O
LRC	O
word	O
at	O
the	O
end	O
of	O
a	O
block	O
of	O
data	O
is	O
very	O
similar	O
to	O
checksum	B-Algorithm
and	O
cyclic	O
redundancy	O
check	O
(	O
CRC	O
)	O
.	O
</s>
<s>
While	O
simple	O
longitudinal	O
parity	B-Error_Name
can	O
only	O
detect	B-Error_Name
errors	O
,	O
it	O
can	O
be	O
combined	O
with	O
additional	O
error-control	O
coding	O
,	O
such	O
as	O
a	O
transverse	B-Error_Name
redundancy	I-Error_Name
check	I-Error_Name
(	O
TRC	O
)	O
,	O
to	O
correct	B-Error_Name
errors	O
.	O
</s>
<s>
The	O
transverse	B-Error_Name
redundancy	I-Error_Name
check	I-Error_Name
is	O
stored	O
on	O
a	O
dedicated	O
"	O
parity	B-Error_Name
track	O
"	O
.	O
</s>
<s>
Whenever	O
any	O
single-bit	O
error	O
occurs	O
in	O
a	O
transmission	O
block	O
of	O
data	O
,	O
such	O
two-dimensional	O
parity	B-Error_Name
checking	I-Error_Name
,	O
or	O
"	O
two-coordinate	O
parity	B-Error_Name
checking	I-Error_Name
"	O
,	O
</s>
<s>
enables	O
the	O
receiver	O
to	O
use	O
the	O
TRC	O
to	O
detect	B-Error_Name
which	O
byte	O
the	O
error	O
occurred	O
in	O
,	O
and	O
the	O
LRC	O
to	O
detect	B-Error_Name
exactly	O
which	O
track	O
the	O
error	O
occurred	O
in	O
,	O
to	O
discover	O
exactly	O
which	O
bit	O
is	O
in	O
error	O
,	O
and	O
then	O
correct	B-Error_Name
that	O
bit	O
by	O
flipping	O
it	O
.	O
</s>
<s>
International	O
standard	O
ISO	B-Error_Name
1155	I-Error_Name
states	O
that	O
a	O
longitudinal	B-Error_Name
redundancy	I-Error_Name
check	I-Error_Name
for	O
a	O
sequence	O
of	O
bytes	O
may	O
be	O
computed	O
in	O
software	O
by	O
the	O
following	O
algorithm	O
:	O
</s>
<s>
Many	O
protocols	O
use	O
an	O
XOR-based	O
longitudinal	B-Error_Name
redundancy	I-Error_Name
check	I-Error_Name
byte	O
(	O
often	O
called	O
block	O
check	O
character	O
or	O
BCC	O
)	O
,	O
including	O
the	O
serial	O
line	O
interface	O
protocol	O
(	O
SLIP	O
,	O
not	O
to	O
be	O
confused	O
with	O
the	O
later	O
and	O
well-known	O
Serial	B-Protocol
Line	I-Protocol
Internet	I-Protocol
Protocol	I-Protocol
)	O
,	O
</s>
<s>
the	O
IEC	O
62056-21	O
standard	O
for	O
electrical-meter	O
reading	O
,	O
smart	O
cards	O
as	O
defined	O
in	O
ISO/IEC	O
7816	O
,	O
and	O
the	O
ACCESS.bus	B-Architecture
protocol	O
.	O
</s>
