<s>
An	O
Ethernet	B-Protocol
extender	I-Protocol
(	O
also	O
network	B-Protocol
extender	I-Protocol
or	O
LAN	B-Protocol
extender	I-Protocol
)	O
is	O
any	O
device	O
used	O
to	O
extend	O
an	O
Ethernet	O
or	O
network	O
segment	O
beyond	O
its	O
inherent	O
distance	O
limitation	O
which	O
is	O
approximately	O
for	O
most	O
common	O
forms	O
of	O
twisted	B-Protocol
pair	I-Protocol
Ethernet	I-Protocol
.	O
</s>
<s>
These	O
devices	O
employ	O
a	O
variety	O
of	O
transmission	O
technologies	O
and	O
physical	O
media	O
(	O
wireless	O
,	O
copper	O
wire	O
,	O
fiber-optic	B-Architecture
cable	I-Architecture
,	O
coaxial	O
cable	O
)	O
.	O
</s>
<s>
The	O
extender	O
forwards	O
traffic	O
between	O
LANs	B-General_Concept
transparent	O
to	O
higher	O
network-layer	O
protocols	O
over	O
distances	O
that	O
far	O
exceed	O
the	O
limitations	O
of	O
standard	O
Ethernet	O
.	O
</s>
<s>
Extenders	O
that	O
use	O
copper	O
wire	O
include	O
2	O
-	O
and	O
4-wire	O
variants	O
using	O
unconditioned	O
copper	O
wiring	O
to	O
extend	O
a	O
LAN	B-General_Concept
.	O
</s>
<s>
Network	B-Protocol
extenders	I-Protocol
use	O
various	O
methods	O
(	O
line	O
encodings	O
)	O
,	O
such	O
as	O
TC-PAM	B-Device
,	O
2B1Q	B-Protocol
or	O
DMT	B-Protocol
,	O
to	O
transmit	O
information	O
.	O
</s>
<s>
While	O
transmitting	O
over	O
copper	O
wire	O
does	O
not	O
allow	O
for	O
the	O
speeds	O
that	O
fiber-optic	B-Architecture
transmission	O
does	O
,	O
it	O
allows	O
the	O
use	O
of	O
existing	O
voice-grade	B-Protocol
copper	I-Protocol
or	O
CCTV	O
coaxial	O
cable	O
wiring	O
.	O
</s>
<s>
Copper-based	O
Ethernet	B-Protocol
extenders	I-Protocol
must	O
be	O
used	O
on	O
unconditioned	O
wire	O
(	O
without	O
load	O
coils	O
)	O
,	O
such	O
as	O
unused	O
twisted	O
pairs	O
and	O
alarm	B-Architecture
circuits	I-Architecture
.	O
</s>
<s>
Connecting	O
a	O
private	O
LAN	B-General_Concept
between	O
buildings	O
or	O
more	O
distant	O
locations	O
is	O
a	O
challenge	O
.	O
</s>
<s>
Fiber	B-Architecture
optic	I-Architecture
connection	O
is	O
ideal	O
,	O
allowing	O
connections	O
of	O
over	O
a	O
km	O
and	O
high	O
speeds	O
with	O
no	O
electrical	O
shock	O
or	O
surge	O
issues	O
,	O
but	O
is	O
technically	O
specialized	O
and	O
expensive	O
for	O
both	O
the	O
end	O
equipment	O
interfaces	O
and	O
the	O
cable	O
.	O
</s>
<s>
Specialized	O
equipment	O
can	O
inter-connect	O
two	O
LANs	B-General_Concept
over	O
a	O
single	O
twisted	O
pair	O
of	O
wires	O
,	O
such	O
as	O
the	O
Moxa	O
IEX	O
Series	O
,	O
Cisco	O
LRE	B-Protocol
(	O
Long	B-Protocol
Reach	I-Protocol
Ethernet	I-Protocol
)	O
,	O
Enable-IT	O
Ethernet	B-Protocol
Extender	I-Protocol
Experts	O
VDSL2	O
,	O
Patton	O
CopperLink	O
or	O
EtherWAN	O
Ethernet	B-Protocol
Extenders	I-Protocol
using	O
VDSL	O
technology	O
.	O
</s>
<s>
Ordinary	O
ADSL	O
modems	O
cannot	O
be	O
connected	O
back-to-back	O
,	O
because	O
the	O
ATU-R	O
(	O
ADSL	O
Termination	O
Unit	O
-	O
Remote	O
)	O
units	O
that	O
are	O
used	O
by	O
customers	O
require	O
specialized	O
ATU-C	O
(	O
Central	O
Office	O
)	O
support	O
provided	O
by	O
phone	O
company	O
equipment	O
,	O
usually	O
by	O
a	O
complex	O
and	O
expensive	O
DSLAM	B-Protocol
(	O
DSL	B-Protocol
access	I-Protocol
multiplexer	I-Protocol
)	O
.	O
</s>
<s>
Similar	O
technologies	O
were	O
standardized	O
as	O
Ethernet	B-Protocol
in	I-Protocol
the	I-Protocol
first	I-Protocol
mile	I-Protocol
:	O
</s>
<s>
2BASE-TL	B-Protocol
Full-duplex	O
long	O
reach	O
point-to-point	B-Architecture
link	I-Architecture
over	O
voice-grade	B-Protocol
copper	I-Protocol
wiring	O
.	O
</s>
<s>
2BASE-TL	B-Protocol
PHY	O
can	O
deliver	O
a	O
minimum	O
of	O
2	O
Mbit/s	O
and	O
a	O
maximum	O
of	O
5.69	O
Mbit/s	O
over	O
distances	O
of	O
up	O
to	O
2700	O
m	O
(	O
9,000	O
ft	O
)	O
,	O
using	O
ITU-T	O
G.991.2	O
(	O
G.SHDSL.bis	O
)	O
technology	O
over	O
a	O
single	O
copper	O
pair	O
.	O
</s>
<s>
10PASS-TS	O
Full-duplex	O
short	O
reach	O
Point-to-Point	B-Architecture
link	I-Architecture
over	O
voice-grade	B-Protocol
copper	I-Protocol
wiring	O
.	O
</s>
