<s>
Basic	B-Protocol
Rate	I-Protocol
Interface	I-Protocol
(	O
BRI	O
,	O
2B+D	B-Protocol
,	O
2B1D	B-Protocol
)	O
or	O
Basic	B-Protocol
Rate	I-Protocol
Access	I-Protocol
is	O
an	O
Integrated	B-Protocol
Services	I-Protocol
Digital	I-Protocol
Network	I-Protocol
(	O
ISDN	B-Protocol
)	O
configuration	O
intended	O
primarily	O
for	O
use	O
in	O
subscriber	B-Architecture
lines	I-Architecture
similar	O
to	O
those	O
that	O
have	O
long	O
been	O
used	O
for	O
voice-grade	O
telephone	O
service	O
.	O
</s>
<s>
As	O
such	O
,	O
an	O
ISDN	B-Protocol
BRI	I-Protocol
connection	O
can	O
use	O
the	O
existing	O
telephone	O
infrastructure	O
at	O
a	O
business	O
.	O
</s>
<s>
The	O
BRI	O
configuration	O
provides	O
2	O
data	O
(	O
bearer	O
)	O
channels	O
(	O
B	B-Protocol
channels	I-Protocol
)	O
at	O
64	O
kbit/s	O
each	O
and	O
1	O
control	O
(	O
delta	O
)	O
channel	O
(	O
D	B-Protocol
channel	I-Protocol
)	O
at	O
16	O
kbit/s	O
.	O
</s>
<s>
The	O
B	B-Protocol
channels	I-Protocol
are	O
used	O
for	O
voice	O
or	O
user	O
data	O
,	O
and	O
the	O
D	B-Protocol
channel	I-Protocol
is	O
used	O
for	O
any	O
combination	O
of	O
data	O
,	O
control/signaling	O
,	O
and	O
X.25	B-Protocol
packet	B-Protocol
networking	O
.	O
</s>
<s>
The	O
2	O
B	B-Protocol
channels	I-Protocol
can	O
be	O
aggregated	O
by	O
channel	B-Architecture
bonding	I-Architecture
providing	O
a	O
total	O
data	O
rate	O
of	O
128	O
kbit/s	O
.	O
</s>
<s>
The	O
BRI	B-Protocol
ISDN	I-Protocol
service	O
is	O
commonly	O
installed	O
for	O
residential	O
or	O
small	O
business	O
service	O
(	O
ISDN	B-Protocol
PABX	O
)	O
in	O
many	O
countries	O
.	O
</s>
<s>
In	O
contrast	O
to	O
the	O
BRI	O
,	O
the	O
Primary	B-Protocol
Rate	I-Protocol
Interface	I-Protocol
(	O
PRI	O
)	O
configuration	O
provides	O
more	O
B	B-Protocol
channels	I-Protocol
and	O
operates	O
at	O
a	O
higher	O
bit	O
rate	O
.	O
</s>
<s>
The	O
S/T	O
-interface	O
(	O
S0	O
)	O
uses	O
four	O
wires	O
;	O
one	O
pair	O
for	O
the	O
uplink	B-Application
and	O
another	O
pair	O
for	O
the	O
downlink	O
.	O
</s>
<s>
The	O
I.430	O
protocol	O
defines	O
48-bit	O
packets	B-Protocol
comprising	O
16	O
bits	O
from	O
the	O
B1	O
channel	O
,	O
16	O
bits	O
from	O
B2	O
channel	O
,	O
4	O
bits	O
from	O
the	O
D	B-Protocol
channel	I-Protocol
,	O
and	O
12	O
bits	O
used	O
for	O
synchronization	O
purposes	O
.	O
</s>
<s>
These	O
packets	B-Protocol
are	O
sent	O
at	O
a	O
rate	O
of	O
,	O
resulting	O
in	O
a	O
gross	O
bit	O
rate	O
of	O
192	O
kbit/s	O
and	O
-	O
giving	O
the	O
data	O
rates	O
listed	O
above	O
-	O
a	O
maximum	O
possible	O
throughput	O
of	O
.	O
</s>
<s>
The	O
Uk0	O
interface	O
uses	O
one	O
wire	O
pair	O
with	O
echo	O
cancellation	O
for	O
the	O
long	O
last	B-Protocol
mile	I-Protocol
cable	O
between	O
the	O
telephone	O
exchange	O
and	O
the	O
network	B-Protocol
terminator	I-Protocol
.	O
</s>
