<s>
A	O
DSL	B-Algorithm
filter	I-Algorithm
(	O
also	O
DSL	B-Algorithm
splitter	I-Algorithm
or	O
microfilter	O
)	O
is	O
an	O
analog	O
low-pass	B-Algorithm
filter	I-Algorithm
installed	O
between	O
analog	O
devices	O
(	O
such	O
as	O
telephones	O
or	O
analog	O
modems	O
)	O
and	O
a	O
plain	O
old	O
telephone	O
service	O
(	O
POTS	O
)	O
line	O
.	O
</s>
<s>
The	O
DSL	B-Algorithm
filter	I-Algorithm
prevents	O
interference	O
between	O
such	O
devices	O
and	O
a	O
digital	O
subscriber	O
line	O
(	O
DSL	O
)	O
service	O
connected	O
to	O
the	O
same	O
line	O
.	O
</s>
<s>
Without	O
DSL	B-Algorithm
filters	I-Algorithm
,	O
signals	O
or	O
echoes	O
from	O
analog	O
devices	O
at	O
the	O
top	O
of	O
their	O
frequency	O
range	O
can	O
reduce	O
performance	O
and	O
create	O
connection	O
problems	O
with	O
DSL	O
service	O
,	O
while	O
those	O
from	O
the	O
DSL	O
service	O
at	O
the	O
bottom	O
of	O
its	O
range	O
can	O
cause	O
line	O
noise	O
and	O
other	O
problems	O
for	O
analog	O
devices	O
.	O
</s>
<s>
The	O
concept	O
of	O
a	O
low	B-Algorithm
pass	I-Algorithm
filter	I-Algorithm
for	O
ADSL	O
was	O
first	O
described	O
in	O
1996	O
by	O
Vic	O
Charlton	O
when	O
working	O
for	O
the	O
Canadian	O
Operations	O
Development	O
Consortium	O
:	O
Low-Pass	B-Algorithm
Filter	I-Algorithm
On	O
All	O
Phones	O
.	O
</s>
<s>
DSL	B-Algorithm
filters	I-Algorithm
are	O
passive	O
devices	O
,	O
requiring	O
no	O
power	O
source	O
to	O
operate	O
.	O
</s>
<s>
Typical	O
installation	O
for	O
an	O
existing	O
home	O
involves	O
installing	O
DSL	B-Algorithm
filters	I-Algorithm
on	O
every	O
telephone	O
,	O
fax	O
machine	O
,	O
voice	O
band	O
modem	O
,	O
and	O
other	O
voiceband	O
device	O
in	O
the	O
home	O
,	O
leaving	O
the	O
DSL	O
modem	O
as	O
the	O
only	O
unfiltered	O
device	O
.	O
</s>
<s>
In	O
cases	O
where	O
it	O
is	O
possible	O
to	O
run	O
new	O
cables	O
,	O
it	O
can	O
be	O
advantageous	O
to	O
split	O
the	O
telephone	O
line	O
after	O
it	O
enters	O
the	O
home	O
,	O
installing	O
a	O
single	O
DSL	B-Algorithm
filter	I-Algorithm
on	O
one	O
leg	O
and	O
running	O
it	O
to	O
every	O
jack	B-Protocol
in	O
the	O
home	O
where	O
an	O
analog	O
device	O
will	O
be	O
in	O
use	O
,	O
and	O
dedicating	O
the	O
other	O
(	O
unfiltered	O
)	O
leg	O
to	O
the	O
DSL	O
modem	O
.	O
</s>
<s>
Some	O
devices	O
such	O
as	O
monitored	O
alarms	O
and	O
Telephone	O
Devices	O
for	O
the	O
Deaf	O
,	O
mainly	O
certain	O
older	O
models	O
using	O
an	O
acoustic	B-Device
coupler	I-Device
,	O
may	O
be	O
hardwired	O
and	O
may	O
not	O
easily	O
accept	O
a	O
DSL	B-Algorithm
filter	I-Algorithm
.	O
</s>
<s>
Some	O
of	O
these	O
devices	O
can	O
be	O
successfully	O
filtered	O
with	O
a	O
DSL	B-Algorithm
filter	I-Algorithm
or	O
splitter	O
,	O
especially	O
if	O
the	O
hardwired	O
connection	O
is	O
converted	O
into	O
a	O
jacked	O
connection	O
.	O
</s>
<s>
If	O
Category	B-Protocol
3	I-Protocol
cable	I-Protocol
,	O
Category	B-Protocol
4	I-Protocol
cable	I-Protocol
,	O
or	O
Category	B-Protocol
5	I-Protocol
cable	I-Protocol
was	O
used	O
to	O
wire	O
the	O
premises	O
and	O
at	O
least	O
one	O
pair	O
of	O
wires	O
in	O
the	O
cable	O
is	O
unused	O
,	O
a	O
"	O
whole	O
house	O
"	O
DSL	B-Algorithm
filter	I-Algorithm
can	O
be	O
installed	O
at	O
the	O
point	O
of	O
entry	O
,	O
usually	O
a	O
Network	B-Protocol
Interface	I-Protocol
Device	I-Protocol
(	O
NID	O
)	O
box	O
.	O
</s>
<s>
At	O
the	O
wall	B-Protocol
jack	I-Protocol
where	O
the	O
DSL	O
modem	O
is	O
installed	O
,	O
a	O
commercial	O
2-line	O
splitter	O
adapter	O
is	O
used	O
that	O
puts	O
each	O
line	O
of	O
the	O
cable	O
on	O
its	O
own	O
jack	B-Protocol
port	O
,	O
connected	O
as	O
Line	O
1	O
.	O
</s>
<s>
The	O
telephone	O
,	O
if	O
any	O
,	O
is	O
plugged	O
into	O
the	O
Line	O
1	O
jack	B-Protocol
and	O
the	O
DSL	O
modem	O
is	O
plugged	O
into	O
the	O
Line	O
2	O
jack	B-Protocol
of	O
the	O
adapter	O
,	O
but	O
is	O
fed	O
through	O
the	O
Line	O
1	O
contacts	O
in	O
that	O
jack	B-Protocol
location	O
.	O
</s>
<s>
Since	O
old-style	O
Category	B-Protocol
3	I-Protocol
cables	I-Protocol
contain	O
four	O
parallel	O
strands	O
of	O
wire	O
,	O
there	O
is	O
crosstalk	O
and	O
ADSL	O
signal	O
degradation	O
between	O
pairs	O
,	O
so	O
cable	O
sharing	O
should	O
be	O
limited	O
to	O
20	O
meters	O
(	O
65ft	O
)	O
,	O
or	O
so	O
.	O
</s>
<s>
If	O
the	O
Line	O
2	O
wire	O
pair	O
was	O
originally	O
not	O
connected	O
at	O
the	O
wall	B-Protocol
jack	I-Protocol
where	O
the	O
DSL	O
modem	O
is	O
to	O
be	O
used	O
,	O
it	O
may	O
be	O
necessary	O
to	O
complete	O
this	O
step	O
as	O
well	O
.	O
</s>
