<s>
IBM	B-Device
37xx	I-Device
(	O
or	O
37x5	O
)	O
is	O
a	O
family	O
of	O
IBM	B-Architecture
Systems	I-Architecture
Network	I-Architecture
Architecture	I-Architecture
(	O
SNA	O
)	O
programmable	O
communications	O
controllers	O
used	O
mainly	O
in	O
mainframe	B-Architecture
environments	I-Architecture
.	O
</s>
<s>
Emulation	O
Program	O
(	O
EP	O
)	O
mimicked	O
the	O
operation	O
of	O
the	O
older	O
IBM	B-Device
270x	I-Device
non-programmable	O
controllers	O
.	O
</s>
<s>
Network	B-Protocol
Control	I-Protocol
Program	I-Protocol
(	O
NCP	O
)	O
supported	O
Systems	B-Architecture
Network	I-Architecture
Architecture	I-Architecture
devices	O
.	O
</s>
<s>
3705	B-Device
the	O
oldest	O
of	O
the	O
family	O
,	O
introduced	O
in	O
1972	O
to	O
replace	O
the	O
non-programmable	O
IBM	B-Device
270x	I-Device
family	O
.	O
</s>
<s>
The	O
3705	B-Device
could	O
control	O
up	O
to	O
352	O
communications	O
lines	O
.	O
</s>
<s>
The	O
3725	O
and	O
the	O
3720	B-Device
systems	O
were	O
announced	O
in	O
1983	O
.	O
</s>
<s>
The	O
3725	O
was	O
a	O
large-scale	O
node	O
and	O
front	B-General_Concept
end	I-General_Concept
processor	I-General_Concept
.	O
</s>
<s>
The	O
3720	B-Device
was	O
a	O
smaller	O
version	O
of	O
the	O
3725	O
,	O
which	O
was	O
sometimes	O
used	O
as	O
a	O
remote	O
concentrator	O
.	O
</s>
<s>
With	O
the	O
expansion	O
unit	O
,	O
the	O
3725	O
could	O
support	O
up	O
to	O
256	O
lines	O
at	O
data	O
rates	O
up	O
to	O
256	O
kbit/s	O
,	O
and	O
connect	O
to	O
up	O
to	O
eight	O
mainframe	B-Architecture
channels	O
.	O
</s>
<s>
IBM	O
discontinued	O
support	O
for	O
the	O
3705	B-Device
,	O
3720	B-Device
,	O
3725	O
in	O
1999	O
.	O
</s>
<s>
The	O
3745	B-Device
,	O
announced	O
in	O
1988	O
,	O
provides	O
up	O
to	O
eight	O
T1	B-Protocol
circuits	I-Protocol
.	O
</s>
<s>
The	O
3745	B-Device
is	O
no	O
longer	O
marketed	O
,	O
but	O
still	O
supported	O
and	O
used	O
.	O
</s>
<s>
The	O
3746	B-Device
"	O
Nways	O
Controller	O
"	O
model	O
900	O
,	O
unveiled	O
in	O
1992	O
,	O
was	O
an	O
expansion	O
unit	O
for	O
the	O
3745	B-Device
supporting	O
additional	O
Token	B-Device
Ring	I-Device
and	O
ESCON	B-Device
connections	O
.	O
</s>
<s>
IBM	O
no	O
longer	O
manufactures	O
37xx	B-Device
processors	O
.	O
</s>
<s>
The	O
last	O
models	O
,	O
the	O
3745/46	O
,	O
were	O
withdrawn	O
from	O
marketing	O
in	O
2002	O
.	O
</s>
<s>
Replacement	O
software	O
products	O
are	O
Communications	B-Application
Controller	I-Application
for	I-Application
Linux	I-Application
on	I-Application
System	I-Application
z	I-Application
and	O
Enterprise	O
Extender	O
.	O
</s>
<s>
Several	O
companies	O
produced	O
clones	O
of	O
37xx	B-Device
controllers	O
,	O
including	O
NCR	O
COMTEN	O
and	O
Amdahl	O
Corporation	O
.	O
</s>
