<s>
+	O
Comparison	B-Protocol
of	I-Protocol
T-carrier	I-Protocol
and	I-Protocol
E-carrier	I-Protocol
systems	I-Protocol
System	O
North	O
American	O
Japanese	O
European	O
(	O
CEPT	O
)	O
Level	O
zero	O
(	O
channel	O
data	O
rate	O
)	O
64	O
kbit/s	O
(	O
DS0	O
)	O
64	O
kbit/s	O
64	O
kbit/s	O
First	O
level	O
1.544	O
Mbit/s	O
(	O
DS1	B-Protocol
)	O
(	O
24	O
user	O
channels	O
)	O
(	O
T1	O
)	O
1.544	O
Mbit/s	O
(	O
24	O
user	O
channels	O
)	O
2.048	O
Mbit/s	O
(	O
32	O
user	O
channels	O
)	O
(	O
E1	O
)	O
(	O
Intermediate	O
level	O
,	O
T-carrier	O
hierarchy	O
only	O
)	O
3.152	O
Mbit/s	O
(	O
DS1C	O
)	O
(	O
48	O
Ch	O
.	O
)	O
</s>
<s>
The	O
DS	B-Protocol
designations	I-Protocol
are	O
used	O
in	O
connection	O
with	O
the	O
North	O
American	O
hierarchy	O
only	O
.	O
</s>
<s>
Strictly	O
speaking	O
,	O
a	O
DS1	B-Protocol
is	O
the	O
data	O
carried	O
on	O
a	O
T1	B-Protocol
circuit	I-Protocol
,	O
and	O
likewise	O
for	O
a	O
DS3	O
and	O
a	O
T3	O
,	O
but	O
in	O
practice	O
the	O
terms	O
are	O
used	O
interchangeably	O
.	O
</s>
<s>
There	O
are	O
other	O
data	O
rates	O
in	O
use	O
,	O
e.g.	O
,	O
military	O
systems	O
that	O
operate	O
at	O
six	O
and	O
eight	O
times	O
the	O
DS1	B-Protocol
rate	O
.	O
</s>
<s>
New	O
systems	O
,	O
which	O
take	O
advantage	O
of	O
the	O
high	O
data	O
rates	O
offered	O
by	O
optical	B-Architecture
communications	O
links	O
,	O
are	O
also	O
deployed	O
or	O
are	O
under	O
development	O
.	O
</s>
<s>
Higher	O
data	O
rates	O
are	O
now	O
often	O
achieved	O
by	O
using	O
synchronous	B-Protocol
optical	I-Protocol
networking	I-Protocol
(	O
SONET	B-Protocol
)	O
or	O
synchronous	B-Protocol
digital	I-Protocol
hierarchy	I-Protocol
(	O
SDH	O
)	O
.	O
</s>
<s>
DS3	O
may	O
be	O
converted	O
to	O
an	O
optical	B-Architecture
fiber	I-Architecture
run	O
when	O
needing	O
longer	O
distances	O
between	O
termination	O
points	O
.	O
</s>
<s>
When	O
delivering	O
data	O
over	O
an	O
OC3	B-Protocol
or	O
greater	O
SONET	B-Protocol
is	O
used	O
.	O
</s>
<s>
A	O
DS3	O
transported	O
over	O
SONET	B-Protocol
is	O
encapsulated	O
in	O
a	O
STS-1	O
SONET	B-Protocol
channel	O
.	O
</s>
<s>
An	O
OC-3	O
SONET	B-Protocol
link	O
contains	O
three	O
STS-1s	O
,	O
and	O
therefore	O
may	O
carry	O
three	O
DS3s	O
.	O
</s>
