<s>
A	O
remote	B-Device
terminal	I-Device
unit	I-Device
(	O
RTU	O
)	O
is	O
a	O
microprocessor-controlled	O
electronic	O
device	O
that	O
interfaces	O
objects	O
in	O
the	O
physical	O
world	O
to	O
a	O
distributed	O
control	O
system	O
or	O
SCADA	O
(	O
supervisory	O
control	O
and	O
data	O
acquisition	O
)	O
system	O
by	O
transmitting	O
telemetry	O
data	O
to	O
a	O
master	O
system	O
,	O
and	O
by	O
using	O
messages	O
from	O
the	O
master	O
supervisory	O
system	O
to	O
control	O
connected	O
objects	O
.	O
</s>
<s>
Other	O
terms	O
that	O
may	O
be	O
used	O
for	O
RTU	O
are	O
remote	B-Device
telemetry	I-Device
unit	I-Device
and	O
remote	B-Device
telecontrol	I-Device
unit	I-Device
.	O
</s>
<s>
Modern	O
RTUs	O
typically	O
support	O
the	O
IEC	O
61131-3	O
programming	O
standard	O
for	O
programmable	B-Architecture
logic	I-Architecture
controllers	I-Architecture
.	O
</s>
<s>
For	O
example	O
,	O
it	O
communicates	O
via	O
RS485	O
or	O
wireless	O
communication	O
links	O
in	O
a	O
multi-drop	B-Architecture
configuration	O
.	O
</s>
<s>
The	O
RTU	O
or	O
host	O
system	O
translates	O
and	O
scales	O
this	O
raw	O
data	O
into	O
the	O
appropriate	O
units	O
such	O
as	O
the	O
quantity	O
of	O
water	O
left	O
,	O
temperature	O
degrees	O
,	O
or	O
Megawatts	O
,	O
before	O
presenting	O
the	O
data	O
to	O
the	O
user	O
via	O
the	O
human	B-Application
–	I-Application
machine	I-Application
interface	I-Application
.	O
</s>
<s>
RTU	O
outputs	O
may	O
also	O
consist	O
of	O
driving	O
a	O
sensitive	O
logic	O
input	O
on	O
an	O
electronic	O
PLC	B-Architecture
,	O
or	O
other	O
electronic	O
device	O
using	O
a	O
sensitive	O
5V	O
input	O
.	O
</s>
<s>
Modern	O
RTUs	O
are	O
usually	O
capable	O
of	O
executing	O
simple	O
programs	O
autonomously	O
without	O
involving	O
the	O
host	O
computers	O
of	O
the	O
DCS	O
or	O
SCADA	O
system	O
to	O
simplify	O
deployment	O
and	O
to	O
provide	O
redundancy	B-Application
for	O
safety	O
reasons	O
.	O
</s>
<s>
An	O
RTU	O
may	O
support	O
standard	O
protocols	O
(	O
Modbus	B-Protocol
,	O
IEC	O
60870-5-101/103/104	O
,	O
DNP3	B-Protocol
,	O
IEC	O
60870-6-ICCP	O
,	O
IEC	O
61850	O
etc	O
.	O
)	O
</s>
<s>
Multiple	O
RTUs	O
or	O
IEDs	O
may	O
share	O
a	O
communications	O
line	O
,	O
in	O
a	O
multi-drop	B-Architecture
scheme	I-Architecture
,	O
as	O
units	O
are	O
addressed	O
uniquely	O
and	O
only	O
respond	O
to	O
their	O
own	O
polls	O
and	O
commands	O
.	O
</s>
<s>
Communications	O
are	O
accomplished	O
by	O
copper	O
or	O
fibre	B-Application
optics	I-Application
lines	I-Application
.	O
</s>
<s>
Remote	B-Application
monitoring	I-Application
and	I-Application
control	I-Application
of	O
functions	O
and	O
instrumentation	O
for	O
:	O
</s>
