<s>
A	O
digital	B-Architecture
cross-connect	I-Architecture
system	I-Architecture
(	O
DCS	O
or	O
DXC	O
)	O
is	O
a	O
piece	O
of	O
circuit-switched	B-Protocol
network	I-Protocol
equipment	O
,	O
used	O
in	O
telecommunications	O
networks	O
,	O
that	O
allows	O
lower-level	O
TDM	B-Protocol
bit	O
streams	O
,	O
such	O
as	O
DS0	O
bit	O
streams	O
,	O
to	O
be	O
rearranged	O
and	O
interconnected	O
among	O
higher-level	O
TDM	B-Protocol
signals	O
,	O
such	O
as	O
DS1	B-Protocol
bit	O
streams	O
.	O
</s>
<s>
DCS	O
units	O
are	O
available	O
that	O
operate	O
on	O
both	O
older	O
T-carrier/E	O
-carrier	O
bit	O
streams	O
,	O
as	O
well	O
as	O
newer	O
SONET/SDH	B-Protocol
bit	O
streams	O
.	O
</s>
<s>
Having	O
a	O
DCS	O
in	O
a	O
circuit-switched	B-Protocol
network	I-Protocol
provides	O
important	O
flexibility	O
that	O
can	O
otherwise	O
only	O
be	O
obtained	O
at	O
higher	O
cost	O
using	O
manual	O
"	O
DSX	O
"	O
cross-connect	B-Architecture
patch	B-Protocol
panels	I-Protocol
.	O
</s>
<s>
It	O
is	O
important	O
to	O
realize	O
that	O
while	O
DCS	O
devices	O
"	O
switch	O
"	O
traffic	O
,	O
they	O
are	O
not	O
packet	O
switchesthey	O
switch	O
circuits	O
,	O
not	O
packets	O
,	O
and	O
the	O
circuit	O
arrangements	O
they	O
are	O
used	O
to	O
manage	O
tend	O
to	O
persist	O
over	O
very	O
long	O
time	O
spans	O
,	O
typically	O
months	O
or	O
longer	O
,	O
as	O
compared	O
to	O
packet	B-Protocol
switches	I-Protocol
,	O
which	O
can	O
route	O
every	O
packet	O
differently	O
,	O
and	O
operate	O
on	O
micro	O
-	O
or	O
millisecond	O
time	O
spans	O
.	O
</s>
<s>
Modern	O
digital	B-Architecture
access	I-Architecture
and	I-Architecture
cross-connect	I-Architecture
systems	I-Architecture
are	O
not	O
limited	O
to	O
the	O
T-carrier	O
system	O
,	O
and	O
may	O
accommodate	O
high	O
data	O
rates	O
such	O
as	O
those	O
of	O
SONET	B-Protocol
.	O
</s>
<s>
Transmuxing	O
(	O
transmux	O
:	O
transcode	O
multiplexing	O
)	O
is	O
a	O
telecommunications	O
signaling	O
format	O
change	O
between	O
two	O
signaling	O
methods	O
,	O
typically	O
synchronous	B-Protocol
optical	I-Protocol
network	I-Protocol
signals	O
,	O
SONET	B-Protocol
,	O
and	O
various	O
time-division	B-Protocol
multiplexing	I-Protocol
,	O
TDM	B-Protocol
,	O
signals	O
.	O
</s>
<s>
Transmuxing	O
changes	O
the	O
“	O
container	O
”	O
without	O
changing	O
the	O
“	O
contents.	O
”	O
Transmuxing	O
provides	O
the	O
carrier	O
the	O
capability	O
to	O
embed	O
a	O
telecommunications	O
signal	O
from	O
one	O
logical	O
TDM	B-Protocol
circuit	O
to	O
another	O
within	O
SONET	B-Protocol
without	O
physically	O
breaking	O
down	O
the	O
TDM	B-Protocol
circuit	O
into	O
its	O
components	O
and	O
reconstructing	O
it	O
.	O
</s>
<s>
In	O
electrical	O
transmuxing	O
,	O
TDM	B-Protocol
signals	O
(	O
typically	O
DS1/T1	O
or	O
DS3	O
)	O
are	O
brought	O
in	O
using	O
copper	O
connections	O
,	O
transmuxed	O
to	O
SONET	B-Protocol
and	O
transported	O
across	O
the	O
network	O
until	O
the	O
reverse	O
occurs	O
.	O
</s>
<s>
In	O
optical	O
transmuxing	O
,	O
TDM	B-Protocol
signals	O
(	O
DS1/T1	O
,	O
DS3	O
,	O
OCx	O
)	O
are	O
brought	O
in	O
using	O
fiber	O
optics	O
,	O
transmuxed	O
to	O
SONET	B-Protocol
and	O
transported	O
across	O
the	O
network	O
until	O
the	O
reverse	O
occurs	O
.	O
</s>
<s>
In	O
the	O
U.S.	O
and	O
Japan	O
,	O
DS1/T1	O
signals	O
are	O
transmuxed	O
into	O
a	O
SONET	B-Protocol
virtual	O
tributary	O
called	O
a	O
VT1.5	O
.	O
</s>
<s>
In	O
TDM	B-Protocol
,	O
24	O
DS0	O
signals	O
are	O
grouped	O
into	O
a	O
DS1/T1	O
signal	O
and	O
28	O
DS1/T1	O
signals	O
are	O
groomed	O
into	O
a	O
DS3	O
signal	O
.	O
</s>
<s>
Circuit	B-Protocol
switching	I-Protocol
is	O
the	O
process	O
of	O
redirecting	O
data	O
signals	O
from	O
one	O
input	O
location	O
to	O
another	O
.	O
</s>
<s>
Common	O
signals	O
connecting	O
to	O
a	O
DCS	O
are	O
at	O
the	O
Electrical	O
-	O
DS1	B-Protocol
,	O
DS3	O
levels	O
and	O
Optical	O
(	O
OCx	O
)	O
-	O
OC3	O
,	O
OC12	O
,	O
OC48	O
,	O
and	O
OC192	O
.	O
</s>
<s>
This	O
is	O
performed	O
at	O
the	O
lowest	O
level	O
possible	O
-	O
DS1	B-Protocol
level	O
(	O
or	O
VT1.5	O
)	O
is	O
preferred	O
.	O
</s>
<s>
A	O
SONET	B-Protocol
3/1	O
DCS	O
will	O
transmux	O
and	O
carry	O
DS3	O
signals	O
as	O
STS-1	O
signals	O
and	O
groom	O
TDM	B-Protocol
DS1/T1s	O
using	O
VT1.5	O
signals	O
.	O
</s>
<s>
If	O
an	O
Electrical	O
DS3	O
is	O
received	O
,	O
it	O
would	O
be	O
connected	O
to	O
an	O
Electrical	O
Transmux	O
port	O
in	O
the	O
DCS	O
where	O
it	O
would	O
be	O
converted	O
from	O
a	O
DS3	O
,	O
demultiplexed	O
back	O
down	O
to	O
the	O
DS1	B-Protocol
level	O
(	O
28	O
DS1s	O
)	O
,	O
overhead	O
would	O
be	O
added	O
to	O
the	O
DS1s	O
to	O
make	O
them	O
VT1.5s	O
and	O
the	O
VT1.5s	O
would	O
be	O
put	O
into	O
an	O
STS-1	O
and	O
sent	O
to	O
the	O
DCS	O
Matrix	O
as	O
a	O
VT	O
mapped	O
STS-1	O
.	O
</s>
