<s>
The	O
IBM	B-Device
3745	I-Device
is	O
the	O
latest	O
and	O
last	O
of	O
a	O
37xx	B-Device
family	I-Device
of	O
communications	O
controllers	O
for	O
the	O
IBM	B-Device
mainframe	I-Device
environment	O
.	O
</s>
<s>
As	O
of	O
mid-2009	O
there	O
were	O
an	O
estimated	O
7,000	O
+	O
of	O
the	O
larger	O
3745	B-Device
models	O
still	O
in	O
active	O
production	O
status	O
,	O
down	O
from	O
20,000	O
or	O
more	O
in	O
2007	O
.	O
</s>
<s>
The	O
3745	B-Device
and	O
associated	O
3746	B-Device
models	O
were	O
once	O
heavily	O
used	O
within	O
financial	O
,	O
insurance	O
and	O
retail	O
industries	O
as	O
well	O
as	O
within	O
government	O
agencies	O
globally	O
.	O
</s>
<s>
However	O
,	O
today	O
most	O
organizations	O
have	O
migrated	O
away	O
from	O
the	O
use	O
of	O
3745s	B-Device
.	O
</s>
<s>
IBM	O
's	O
Enterprise	O
Extender	O
and	O
the	O
Communication	B-Application
Controller	I-Application
for	I-Application
Linux	I-Application
on	I-Application
System	I-Application
z	I-Application
(	O
CCL	O
)	O
have	O
largely	O
displaced	O
the	O
older	O
3745s	B-Device
.	O
</s>
<s>
IBM	O
announced	O
in	O
September	O
2002	O
that	O
it	O
would	O
no	O
longer	O
manufacture	O
new	O
3745s	B-Device
,	O
but	O
IBM	O
continues	O
to	O
support	O
the	O
hardware	O
by	O
providing	O
worldwide	O
maintenance	O
service	O
,	O
by	O
providing	O
microcode	O
releases	O
and	O
by	O
supporting	O
the	O
associated	O
software	O
including	O
NCP	B-Protocol
(	O
Network	O
Control	O
Program	O
)	O
and	O
the	O
virtual	B-Application
telecommunications	I-Application
access	I-Application
method	I-Application
(	O
VTAM	B-Application
)	O
.	O
</s>
<s>
The	O
latest	O
and	O
most	O
commonly	O
used	O
models	O
of	O
the	O
3745	B-Device
are	O
the	O
3745-31A	O
single	O
CCU	O
and	O
3745-61A	O
dual	O
CCU	O
models	O
.	O
</s>
<s>
These	O
are	O
usually	O
operated	O
in	O
conjunction	O
with	O
the	O
3746-900	O
expansion	O
unit	O
(	O
aka	O
900	O
frame	O
)	O
.	O
</s>
<s>
The	O
900	O
frame	O
provides	O
multiple	O
T1	B-Protocol
,	O
token	O
ring	O
,	O
V.35	O
and	O
V.24	O
attachments	O
on	O
the	O
front	O
end	O
,	O
and	O
connects	O
on	O
the	O
back	O
end	O
to	O
the	O
mainframe	O
host	O
with	O
multiple	O
ESCON	B-Device
serial	O
fiber	O
optic	O
channels	O
.	O
</s>
<s>
An	O
operator	O
and	O
service	O
interface	O
to	O
the	O
3745	B-Device
and	O
900	O
frame	O
is	O
provided	O
by	O
an	O
IBM	O
Service	O
Processor	O
which	O
operates	O
under	O
the	O
control	O
of	O
the	O
IBM	B-Application
OS/2	I-Application
operating	O
system	O
and	O
proprietary	O
code	O
.	O
</s>
<s>
IBM	O
maintained	O
a	O
contract	O
manufacturing	O
facility	O
for	O
the	O
3745/3746	O
product	O
set	O
in	O
Havant	O
,	O
Hampshire	O
,	O
United	O
Kingdom	O
until	O
the	O
end	O
of	O
2002	O
.	O
</s>
<s>
When	O
production	O
at	O
Havant	O
ceased	O
,	O
the	O
remaining	O
inventory	O
of	O
new	O
product	O
,	O
features	O
,	O
parts	O
and	O
components	O
was	O
purchased	O
by	O
Mid-Atlantic	O
Research	O
and	O
Services	O
,	O
Inc	O
.	O
That	O
company	O
built	O
and	O
operated	O
a	O
re-manufacturing	O
facility	O
in	O
Maryland	O
,	O
USA	O
for	O
the	O
purpose	O
of	O
providing	O
upgrade	O
kits	O
and	O
service	O
parts	O
for	O
those	O
large	O
companies	O
that	O
continued	O
to	O
rely	O
upon	O
the	O
3745/3746	O
for	O
critical	O
network	O
applications	O
.	O
</s>
<s>
IBM	O
does	O
not	O
market	O
a	O
direct	O
hardware	O
replacement	O
for	O
the	O
IBM	B-Device
3745	I-Device
providing	O
all	O
of	O
the	O
3745/3746	O
interfaces	O
.	O
</s>
<s>
However	O
,	O
IBM	O
offers	O
a	O
software	O
emulation	O
product	O
that	O
provides	O
a	O
subset	O
of	O
3745/3746	O
function	O
,	O
IBM	O
's	O
Communications	B-Application
Controller	I-Application
for	I-Application
Linux	I-Application
on	I-Application
System	I-Application
z	I-Application
.	O
CCL	O
is	O
a	O
software	O
emulation	O
that	O
runs	O
on	O
the	O
mainframe	O
under	O
Linux	B-Application
on	I-Application
System	I-Application
z	I-Application
.	O
</s>
<s>
The	O
NCP	B-Protocol
(	O
Network	O
Control	O
Program	O
)	O
licensed	O
for	O
use	O
in	O
the	O
3745/3746	O
continues	O
to	O
be	O
licensed	O
for	O
use	O
with	O
CCL	O
.	O
</s>
<s>
Alternatively	O
,	O
in	O
many	O
cases	O
it	O
is	O
possible	O
to	O
migrate	O
away	O
from	O
networking	O
protocols	O
supported	O
by	O
the	O
3745	B-Device
and	O
CCL	O
,	O
relying	O
solely	O
on	O
the	O
SNA	B-Architecture
and	O
TCP/IP	B-Protocol
protocol	I-Protocol
support	O
provided	O
by	O
z/OS	O
Communications	O
Server	O
.	O
</s>
