<s>
NMEA	B-Protocol
0183	I-Protocol
is	O
a	O
combined	O
electrical	O
and	O
data	O
specification	O
for	O
communication	O
between	O
marine	O
electronics	O
such	O
as	O
echo	O
sounder	O
,	O
sonars	B-Application
,	O
anemometer	O
,	O
gyrocompass	O
,	O
autopilot	O
,	O
GPS	O
receivers	O
and	O
many	O
other	O
types	O
of	O
instruments	O
.	O
</s>
<s>
It	O
replaces	O
the	O
earlier	O
NMEA	B-Protocol
0180	I-Protocol
and	O
NMEA	B-Protocol
0182	I-Protocol
standards	O
.	O
</s>
<s>
In	O
leisure	O
marine	O
applications	O
it	O
is	O
slowly	O
being	O
phased	O
out	O
in	O
favor	O
of	O
the	O
newer	O
NMEA	O
2000	O
standard	O
,	O
though	O
NMEA	B-Protocol
0183	I-Protocol
remains	O
the	O
norm	O
in	O
commercial	O
shipping	O
.	O
</s>
<s>
The	O
electrical	O
standard	O
that	O
is	O
used	O
is	O
EIA-422	O
,	O
although	O
most	O
hardware	O
with	O
NMEA-0183	B-Protocol
outputs	O
are	O
also	O
able	O
to	O
drive	O
a	O
single	O
EIA-232	O
port	O
.	O
</s>
<s>
The	O
NMEA	B-Protocol
0183	I-Protocol
standard	O
uses	O
a	O
simple	O
ASCII	B-Protocol
,	O
serial	B-Protocol
communications	I-Protocol
protocol	O
that	O
defines	O
how	O
data	O
are	O
transmitted	O
in	O
a	O
"	O
sentence	O
"	O
from	O
one	O
"	O
talker	O
"	O
to	O
multiple	O
"	O
listeners	O
"	O
at	O
a	O
time	O
.	O
</s>
<s>
Through	O
the	O
use	O
of	O
intermediate	O
expanders	O
,	O
a	O
talker	O
can	O
have	O
a	O
unidirectional	O
conversation	O
with	O
a	O
nearly	O
unlimited	O
number	O
of	O
listeners	O
,	O
and	O
using	O
multiplexers	B-Protocol
,	O
multiple	O
sensors	O
can	O
talk	O
to	O
a	O
single	O
computer	O
port	O
.	O
</s>
<s>
While	O
NMEA0183	B-Protocol
only	O
defines	O
an	O
RS422	O
transport	O
,	O
there	O
also	O
exists	O
a	O
de	O
facto	O
standard	O
in	O
which	O
the	O
sentences	O
from	O
NMEA0183	B-Protocol
are	O
placed	O
in	O
UDP	B-Protocol
datagrams	O
(	O
one	O
sentence	O
per	O
packet	O
)	O
and	O
sent	O
over	O
an	O
IP	O
network	O
.	O
</s>
<s>
All	O
transmitted	O
data	O
are	O
printable	O
ASCII	B-Protocol
characters	I-Protocol
between	O
0x20	O
(	O
space	O
)	O
to	O
0x7e	O
(	O
~	O
)	O
</s>
<s>
Reserved	O
characters	O
are	O
used	O
by	O
NMEA0183	B-Protocol
for	O
the	O
following	O
uses	O
:	O
</s>
<s>
ASCII	B-Protocol
Hex	O
Dec	O
Use	O
<CR>  0x0d  13  Carriage return <LF>	O
0x0a	O
10	O
Line	O
feed	O
,	O
end	O
delimiter	O
!	O
</s>
<s>
The	O
first	O
character	O
that	O
immediately	O
follows	O
the	O
last	O
data	O
field	O
character	O
is	O
an	O
asterisk	O
,	O
but	O
it	O
is	O
only	O
included	O
if	O
a	O
checksum	B-Algorithm
is	O
supplied	O
.	O
</s>
<s>
The	O
asterisk	O
is	O
immediately	O
followed	O
by	O
a	O
checksum	B-Algorithm
represented	O
as	O
a	O
two-digit	O
hexadecimal	O
number	O
.	O
</s>
<s>
The	O
checksum	B-Algorithm
is	O
the	O
bitwise	O
exclusive	O
OR	O
of	O
ASCII	B-Protocol
codes	I-Protocol
of	O
all	O
characters	O
between	O
the	O
$	O
and	O
*	O
,	O
not	O
inclusive	O
.	O
</s>
<s>
According	O
to	O
the	O
official	O
specification	O
,	O
the	O
checksum	B-Algorithm
is	O
optional	O
for	O
most	O
data	O
sentences	O
,	O
but	O
is	O
compulsory	O
for	O
RMA	O
,	O
RMB	O
,	O
and	O
RMC	O
(	O
among	O
others	O
)	O
.	O
</s>
<s>
NMEA	B-Protocol
0183	I-Protocol
is	O
supported	O
by	O
various	O
navigation	O
and	O
mapping	O
software	O
.	O
</s>
<s>
NMEA	B-Protocol
0183	I-Protocol
continued	O
to	O
be	O
maintained	O
separately	O
:	O
V4.10	O
was	O
published	O
in	O
early	O
May	O
2012	O
,	O
and	O
an	O
erratum	O
noted	O
on	O
12	O
May	O
2012	O
.	O
</s>
