<s>
The	O
Model	O
F	O
was	O
a	O
series	O
of	O
computer	B-Device
keyboards	I-Device
produced	O
mainly	O
from	O
1981	O
–	O
1985	O
and	O
in	O
reduced	O
volume	O
until	O
1994	O
by	O
IBM	O
and	O
later	O
Lexmark	O
.	O
</s>
<s>
Its	O
mechanical-key	O
design	O
consisted	O
of	O
a	O
buckling	B-Device
spring	I-Device
over	O
a	O
capacitive	O
PCB	O
,	O
similar	O
to	O
the	O
later	O
Model	B-Device
M	I-Device
keyboard	I-Device
that	O
used	O
a	O
membrane	O
in	O
place	O
of	O
the	O
PCB	O
.	O
</s>
<s>
The	O
Model	O
F	O
first	O
appeared	O
with	O
the	O
IBM	B-Device
System/23	I-Device
Datamaster	I-Device
all-in-one	O
computer	O
.	O
</s>
<s>
It	O
is	O
best	O
known	O
as	O
part	O
of	O
the	O
IBM	B-Device
Personal	I-Device
Computer	I-Device
in	O
1981	O
with	O
some	O
keycap	O
label	O
differences	O
,	O
and	O
its	O
subsequent	O
release	O
with	O
the	O
IBM	B-Operating_System
Personal	I-Operating_System
Computer/AT	I-Operating_System
,	O
where	O
it	O
was	O
reconfigured	O
with	O
the	O
AT	O
protocol	O
and	O
some	O
layout	O
revisions	O
.	O
</s>
<s>
After	O
the	O
introduction	O
of	O
the	O
Model	B-Device
M	I-Device
keyboard	I-Device
,	O
production	O
was	O
ramped	O
down	O
and	O
eventually	O
limited	O
to	O
replacement	O
units	O
for	O
existing	O
installations	O
.	O
</s>
<s>
The	O
capacitive	O
design	O
is	O
widely	O
considered	O
superior	O
to	O
that	O
of	O
the	O
later	O
membrane	O
design	O
used	O
on	O
the	O
Model	B-Device
M	I-Device
.	O
It	O
has	O
a	O
lighter	O
actuation	O
force	O
of	O
about	O
600mN	O
,	O
a	O
crisper	O
feel	O
,	O
and	O
louder	O
feedback	O
.	O
</s>
<s>
It	O
also	O
has	O
a	O
higher	O
MTBF	O
of	O
over	O
100	O
million	O
keypresses	O
,	O
and	O
full	B-Device
n-key	I-Device
rollover	I-Device
.	O
</s>
<s>
These	O
advantages	O
were	O
sacrificed	O
in	O
the	O
Model	B-Device
M	I-Device
in	O
order	O
to	O
lower	O
manufacturing	O
costs	O
.	O
</s>
<s>
Many	O
IBM	O
keyboards	B-Device
were	O
based	O
on	O
Model	O
F	O
technology	O
,	O
featuring	O
different	O
keycaps	O
,	O
layouts	O
and	O
connections	O
:	O
</s>
<s>
Name	O
PN	O
Description	O
Image	O
Model	O
F	O
'	O
XT	O
 '	O
1801449	O
Released	O
in	O
1981	O
with	O
the	O
original	O
IBM	B-Device
PC	I-Device
.	O
</s>
<s>
frameless|upright	O
=	O
0.65	O
|alt	O
=	O
83-key	O
PC/XT	O
keyboard	B-Device
Model	O
F	O
'	O
AT	O
 '	O
6450200	O
(	O
US	O
version	O
)	O
Released	O
in	O
1984	O
with	O
the	O
IBM	B-Operating_System
PC	I-Operating_System
AT	I-Operating_System
.	O
</s>
<s>
frameless|upright	O
=	O
0.65	O
|alt	O
=	O
84-key	O
PC/AT	B-Operating_System
keyboard	B-Device
Model	O
F	O
'	O
122-key	O
terminal	O
keyboard	B-Device
 '	O
611034x	O
Terminal	O
keyboard	B-Device
originally	O
released	O
for	O
the	O
IBM	B-Device
PC	I-Device
3270	O
.	O
</s>
<s>
frameless|upright	O
=	O
0.65	O
|alt	O
=	O
122-key	O
keyboard	B-Device
Model	O
F	O
'	O
104-key	O
terminal	O
keyboard	B-Device
 '	O
1387033	O
Terminal	O
keyboard	B-Device
released	O
for	O
the	O
IBM	O
5085	O
and	O
IBM	O
3290	O
.	O
</s>
<s>
Model	O
F	O
'	O
3178	O
blue	O
switch	O
87-key	O
'	O
6019284	O
87-key	O
keyboard	B-Device
released	O
for	O
the	O
IBM	O
3178	O
,	O
so	O
named	O
because	O
of	O
the	O
blue	O
toggle	O
switch	O
on	O
the	O
top	O
half	O
.	O
</s>
<s>
Model	O
F	O
'	O
4704	O
62-key	O
'	O
6019284	O
62-key	O
keyboard	B-Device
released	O
for	O
the	O
IBM	O
4704	O
Model	O
F	O
'	O
4704	O
107-key	O
'	O
6020218	O
107-key	O
keyboard	B-Device
released	O
for	O
the	O
IBM	O
4704	O
Model	O
F	O
'	O
4704	O
50-key	O
'	O
6019273	O
50-key	O
keypad	O
released	O
for	O
the	O
IBM	O
4704	O
Model	O
F	O
'	O
Displaywriter	B-Protocol
 '	O
?	O
</s>
<s>
Keyboard	B-Device
released	O
for	O
the	O
IBM	B-Protocol
Displaywriter	I-Protocol
System	I-Protocol
,	O
these	O
Model	B-Device
F	I-Device
keyboards	I-Device
featured	O
fully	O
white	O
keys	O
.	O
</s>
<s>
The	O
enthusiast	O
community	O
around	O
the	O
Model	B-Device
M	I-Device
keyboard	I-Device
also	O
prizes	O
Model	O
Fs	O
and	O
restores	O
them	O
for	O
use	O
with	O
modern	O
systems	O
,	O
though	O
fewer	O
are	O
still	O
in	O
use	O
due	O
to	O
lower	O
production	O
volume	O
and	O
a	O
layout	O
that	O
is	O
somewhat	O
awkward	O
and	O
limited	O
by	O
modern	O
standards	O
.	O
</s>
<s>
Since	O
2016	O
a	O
project	O
has	O
been	O
underway	O
to	O
manufacture	O
for	O
sale	O
keyboards	B-Device
with	O
a	O
faithful	O
re-creation	O
of	O
the	O
model	O
F	O
mechanism	O
,	O
completely	O
independently	O
of	O
IBM	O
.	O
</s>
<s>
The	O
New	O
Model	O
F	O
has	O
two	O
variants	O
which	O
both	O
resemble	O
the	O
4704	O
,	O
but	O
with	O
default	O
layouts	O
tweaked	O
in	O
the	O
direction	O
of	O
a	O
Model	B-Device
M	I-Device
(	O
notably	O
using	O
an	O
inverted-T	O
arrow-key	O
cluster	O
rather	O
than	O
the	O
old-fashioned	O
cross	O
layout	O
of	O
the	O
original	O
Model	O
Fs	O
)	O
.	O
</s>
<s>
Earlier	O
Model	B-Device
F	I-Device
keyboards	I-Device
cannot	O
have	O
their	O
space	O
bars	O
removed	O
without	O
disassembling	O
the	O
internal	O
assembly	O
;	O
this	O
also	O
causes	O
a	O
slightly	O
different	O
feel	O
response	O
from	O
the	O
space	O
bar	O
specifically	O
:	O
some	O
enthusiasts	O
modify	O
the	O
tension	O
of	O
the	O
stabilizer	O
on	O
these	O
early	O
Model	B-Device
F	I-Device
keyboards	I-Device
to	O
provide	O
a	O
more	O
satisfactory	O
response	O
.	O
</s>
<s>
The	O
top	O
metal	O
plates	O
in	O
Model	B-Device
F	I-Device
keyboards	I-Device
are	O
prone	O
to	O
corrosion	O
and	O
the	O
internal	O
foam	O
can	O
also	O
rot	O
from	O
age	O
,	O
which	O
often	O
requires	O
cleaning	O
and	O
a	O
coating	O
to	O
prevent	O
further	O
corrosion	O
.	O
</s>
<s>
All	O
Model	O
F	O
internal	O
assemblies	O
are	O
held	O
together	O
with	O
metal	O
tabs	O
,	O
unlike	O
the	O
Model	B-Device
M	I-Device
which	O
uses	O
melted	O
plastic	O
rivets	O
requiring	O
more	O
rivets	O
to	O
be	O
melted	O
on	O
or	O
modified	O
with	O
bolts	O
.	O
</s>
<s>
The	O
later	O
Model	B-Device
M	I-Device
keyboards	I-Device
used	O
injection	O
plastic	O
rather	O
than	O
paint	O
to	O
achieve	O
this	O
texture	O
.	O
</s>
<s>
Although	O
the	O
Model	O
F	O
and	O
Model	B-Device
M	I-Device
are	O
both	O
based	O
on	O
buckling-spring	B-Device
technology	O
,	O
there	O
are	O
considerable	O
differences	O
between	O
them	O
:	O
</s>
