<s>
A	O
3270	B-Application
Emulator	I-Application
is	O
a	O
terminal	B-Application
emulator	I-Application
that	O
duplicates	O
the	O
functions	O
of	O
an	O
IBM	B-Operating_System
3270	I-Operating_System
mainframe	B-General_Concept
computer	I-General_Concept
terminal	I-General_Concept
on	O
a	O
computer	O
,	O
usually	O
a	O
PC	B-Device
or	O
similar	O
microcomputer	B-Architecture
.	O
</s>
<s>
As	O
the	O
original	O
3270	B-Operating_System
series	O
terminals	O
were	O
connected	O
to	O
the	O
host	B-Device
computer	I-Device
through	O
a	O
display	O
controller	O
(	O
cluster	O
controller	O
)	O
using	O
coaxial	O
cable	O
,	O
emulators	O
originally	O
required	O
channel	O
(	O
rare	O
)	O
,	O
coax	O
or	O
synchronous	B-Protocol
communication	I-Protocol
adapter	O
cards	O
to	O
be	O
installed	O
in	O
the	O
PC	B-Device
.	O
</s>
<s>
Today	O
,	O
many	O
emulators	O
communicate	O
with	O
the	O
mainframe	B-Architecture
computer	I-Architecture
through	O
a	O
TN3270	O
server	O
using	O
the	O
TN3270	O
(	O
)	O
variant	O
of	O
the	O
Telnet	B-Protocol
(	O
)	O
protocol	O
common	O
on	O
TCP/IP	B-Protocol
networks	I-Protocol
including	O
the	O
Internet	O
,	O
so	O
special	O
hardware	O
is	O
no	O
longer	O
required	O
on	O
machines	O
with	O
Internet	O
access	O
.	O
</s>
<s>
Several	O
vendors	O
offered	O
both	O
coax	O
and	O
communications	O
attached	O
3270	B-Application
emulators	I-Application
and	O
TN3270	O
clients	O
as	O
part	O
of	O
the	O
same	O
product	O
.	O
</s>
<s>
One	O
way	O
of	O
categorizing	O
a	O
3270	B-Operating_System
simulator	O
is	O
by	O
how	O
it	O
connects	O
to	O
the	O
host	O
.	O
</s>
<s>
Some	O
3270	B-Operating_System
simulators	O
use	O
a	O
channel	O
adapter	O
to	O
connect	O
directly	O
to	O
the	O
host	O
.	O
</s>
<s>
Some	O
3270	B-Operating_System
simulators	O
use	O
a	O
coax	O
adapter	O
such	O
as	O
the	O
Irma	B-Device
board	I-Device
to	O
connect	O
to	O
a	O
cluster	O
controller	O
.	O
</s>
<s>
Some	O
3270	B-Operating_System
simulators	O
use	O
a	O
synchronous	B-Protocol
serial	I-Protocol
link	I-Protocol
to	O
connect	O
to	O
a	O
communications	O
controller	O
.	O
</s>
<s>
Using	O
BSC	B-Protocol
requires	O
less	O
code	O
,	O
but	O
SDLC	B-Protocol
with	O
SNA	B-Architecture
allows	O
more	O
functionality	O
.	O
</s>
<s>
Some	O
3270	B-Operating_System
simulators	O
use	O
a	O
LAN	O
interface	O
to	O
a	O
cluster	O
controller	O
.	O
</s>
<s>
Contemporary	O
3270	B-Operating_System
simulators	O
typically	O
use	O
TN3270	O
to	O
connect	O
to	O
a	O
TN3270	O
server	O
on	O
the	O
host	O
.	O
</s>
<s>
In	O
1983	O
,	O
IBM	O
marketed	O
the	O
IBM	B-Device
3270	I-Device
PC	I-Device
,	O
a	O
bundled	O
package	O
including	O
a	O
PC	B-Device
,	O
a	O
graphics	O
adapter	O
,	O
3270	B-Operating_System
emulation	O
software	O
and	O
coax	O
interface	O
card	O
.	O
</s>
<s>
3270	B-Application
emulators	I-Application
and	O
TN3270	O
clients	O
are	O
also	O
available	O
from	O
many	O
third-party	O
vendors	O
like	O
Attachmate	O
and	O
Ericom	B-Protocol
.	O
</s>
