<s>
In	O
the	O
Integrated	B-Protocol
Services	I-Protocol
Digital	I-Protocol
Network	I-Protocol
(	O
ISDN	B-Protocol
)	O
,	O
a	O
high-speed	O
communication	O
channel	O
comprising	O
multiple	O
aggregated	O
low-speed	O
channels	O
to	O
accommodate	O
bandwidth-intensive	O
applications	O
such	O
as	O
file	B-Protocol
transfer	I-Protocol
,	O
videoconferencing	B-Application
,	O
and	O
high-quality	O
audio	O
.	O
</s>
<s>
An	O
H	B-Protocol
channel	I-Protocol
is	O
formed	O
of	O
multiple	O
bearer	O
B	B-Protocol
channels	I-Protocol
bonded	O
together	O
in	O
a	O
primary	B-Protocol
rate	I-Protocol
access	I-Protocol
(	O
PRA	O
)	O
or	O
primary	B-Protocol
rate	I-Protocol
interface	I-Protocol
(	O
PRI	O
)	O
frame	O
in	O
support	O
of	O
applications	O
with	O
bandwidth	B-Algorithm
requirements	O
that	O
exceed	O
the	O
B	B-Protocol
channel	I-Protocol
rate	O
of	O
64	O
kbit/s	O
.	O
</s>
<s>
The	O
channels	O
,	O
once	O
bonded	O
,	O
remain	O
so	O
end-to-end	O
,	O
from	O
transmitter	O
to	O
receiver	O
,	O
through	O
the	O
ISDN	B-Protocol
network	O
.	O
</s>
<s>
The	O
feature	O
is	O
known	O
variously	O
as	O
multirate	O
ISDN	B-Protocol
,	O
Nx64	O
,	O
channel	O
aggregation	O
,	O
and	O
bonding	B-Architecture
.	O
</s>
<s>
H	B-Protocol
channels	I-Protocol
are	O
implemented	O
as	O
:	O
</s>
<s>
H12	O
=	O
1920	O
kbit/s	O
( 30	O
B	B-Protocol
channels	I-Protocol
)	O
–	O
International	O
(	O
E-carrier	O
)	O
only	O
.	O
</s>
