<s>
The	O
technology	O
of	O
computer	O
keyboards	B-Device
includes	O
many	O
elements	O
.	O
</s>
<s>
Computer	O
alphanumeric	B-Device
keyboards	I-Device
typically	O
have	O
80	O
to	O
110	O
durable	O
switches	B-Device
,	O
generally	O
one	O
for	O
each	O
key	O
.	O
</s>
<s>
Virtual	B-Device
keyboards	I-Device
on	O
touch	B-Device
screens	I-Device
have	O
no	O
physical	O
switches	B-Device
and	O
provide	O
audio	O
and	O
haptic	B-Device
feedback	I-Device
instead	O
.	O
</s>
<s>
Some	O
newer	O
keyboard	B-Device
models	O
use	O
hybrids	O
of	O
various	O
technologies	O
to	O
achieve	O
greater	O
cost	O
savings	O
or	O
better	O
ergonomics	O
.	O
</s>
<s>
The	O
modern	O
keyboard	B-Device
also	O
includes	O
a	O
control	B-Device
processor	O
and	O
indicator	O
lights	O
to	O
provide	O
feedback	O
to	O
the	O
user	O
(	O
and	O
to	O
the	O
central	O
processor	O
)	O
about	O
what	O
state	O
the	O
keyboard	B-Device
is	O
in	O
.	O
</s>
<s>
Plug	B-Device
and	I-Device
play	I-Device
technology	O
means	O
that	O
its	O
"	O
out	O
of	O
the	O
box	O
"	O
layout	O
can	O
be	O
notified	O
to	O
the	O
system	O
,	O
making	O
the	O
keyboard	B-Device
immediately	O
ready	O
to	O
use	O
without	O
need	O
for	O
further	O
configuration	O
,	O
unless	O
the	O
user	O
so	O
desires	O
.	O
</s>
<s>
There	O
are	O
two	O
types	O
of	O
membrane-based	O
keyboards	B-Device
,	O
flat-panel	B-Device
membrane	I-Device
keyboards	I-Device
and	O
full-travel	O
membrane	B-Device
keyboards	I-Device
:	O
</s>
<s>
Flat-panel	B-Device
membrane	I-Device
keyboards	B-Device
are	O
most	O
often	O
found	O
on	O
appliances	O
like	O
microwave	O
ovens	O
or	O
photocopiers	O
.	O
</s>
<s>
This	O
indicates	O
to	O
the	O
computer	O
or	O
keyboard	B-Device
control	B-Device
processor	O
that	O
a	O
particular	O
button	O
has	O
been	O
pressed	O
.	O
</s>
<s>
Generally	O
,	O
flat-panel	B-Device
membrane	I-Device
keyboards	B-Device
do	O
not	O
produce	O
a	O
noticeable	O
physical	O
feedback	O
.	O
</s>
<s>
Although	O
used	O
in	O
the	O
early	O
days	O
of	O
the	O
personal	B-Device
computer	I-Device
(	O
on	O
the	O
Sinclair	B-Operating_System
ZX80	I-Operating_System
,	O
ZX81	O
and	O
Atari	O
400	O
)	O
,	O
they	O
have	O
been	O
supplanted	O
by	O
the	O
more	O
tactile	O
dome	O
and	O
mechanical	O
switch	O
keyboards	B-Device
.	O
</s>
<s>
Full-travel	O
membrane-based	O
keyboards	B-Device
are	O
the	O
most	O
common	O
computer	O
keyboards	B-Device
today	O
.	O
</s>
<s>
Dome-switch	O
keyboards	B-Device
are	O
a	O
hybrid	O
of	O
flat-panel	B-Device
membrane	I-Device
and	O
mechanical-switch	O
keyboards	B-Device
.	O
</s>
<s>
They	O
bring	O
two	O
circuit	O
board	O
traces	O
together	O
under	O
a	O
rubber	O
or	O
silicone	O
keypad	O
using	O
either	O
metal	O
"	O
dome	O
"	O
switches	B-Device
or	O
polyurethane	O
formed	O
domes	O
.	O
</s>
<s>
The	O
metal	O
dome	O
switches	B-Device
are	O
formed	O
pieces	O
of	O
stainless	O
steel	O
that	O
,	O
when	O
compressed	O
,	O
give	O
the	O
user	O
a	O
crisp	O
,	O
positive	O
tactile	O
feedback	O
.	O
</s>
<s>
These	O
metal	O
types	O
of	O
dome	O
switches	B-Device
are	O
very	O
common	O
,	O
are	O
usually	O
reliable	O
to	O
over	O
5	O
million	O
cycles	O
,	O
and	O
can	O
be	O
plated	O
in	O
either	O
nickel	O
,	O
silver	O
or	O
gold	O
.	O
</s>
<s>
The	O
rubber	O
dome	O
switches	B-Device
,	O
occasionally	O
referred	O
to	O
as	O
polydomes	O
,	O
are	O
formed	O
polyurethane	O
domes	O
where	O
the	O
inside	O
bubble	O
is	O
coated	O
in	O
graphite	O
.	O
</s>
<s>
Both	O
are	O
common	O
switch	O
technologies	O
used	O
in	O
mass	O
market	O
keyboards	B-Device
today	O
.	O
</s>
<s>
Dome-switch	O
keyboards	B-Device
are	O
also	O
called	O
direct-switch	O
keyboards	B-Device
.	O
</s>
<s>
A	O
special	O
case	O
of	O
the	O
computer	O
keyboard	B-Device
dome-switch	O
is	O
the	O
scissor-switch	O
.	O
</s>
<s>
The	O
keys	O
are	O
attached	O
to	O
the	O
keyboard	B-Device
via	O
two	O
plastic	O
pieces	O
that	O
interlock	O
in	O
a	O
"	O
scissor	O
"	O
-like	O
fashion	O
,	O
and	O
snap	O
to	O
the	O
keyboard	B-Device
and	O
the	O
key	O
.	O
</s>
<s>
It	O
still	O
uses	O
rubber	O
domes	O
,	O
but	O
a	O
special	O
plastic	O
'	O
scissors	O
 '	O
mechanism	O
links	O
the	O
keycap	B-Device
to	O
a	O
plunger	O
that	O
depresses	O
the	O
rubber	O
dome	O
with	O
a	O
much	O
shorter	O
travel	O
than	O
the	O
typical	O
rubber	O
dome	O
keyboard	B-Device
.	O
</s>
<s>
Typically	O
scissor-switch	O
keyboards	B-Device
also	O
employ	O
3-layer	O
membranes	O
as	O
the	O
electrical	O
component	O
of	O
the	O
switch	O
.	O
</s>
<s>
They	O
also	O
usually	O
have	O
a	O
shorter	O
total	O
key	O
travel	O
distance	O
(	O
2mm	O
instead	O
of	O
3.5	O
–	O
4mm	O
for	O
standard	O
dome-switch	O
keyswitches	B-Device
)	O
.	O
</s>
<s>
This	O
type	O
of	O
keyswitch	B-Device
is	O
often	O
found	O
on	O
the	O
built-in	O
keyboards	B-Device
on	O
laptops	O
and	O
keyboards	B-Device
marketed	O
as	O
'	O
low-profile	O
'	O
.	O
</s>
<s>
These	O
keyboards	B-Device
are	O
generally	O
quiet	O
and	O
the	O
keys	O
require	O
little	O
force	O
to	O
press	O
.	O
</s>
<s>
Scissor-switch	O
keyboards	B-Device
are	O
typically	O
slightly	O
more	O
expensive	O
.	O
</s>
<s>
They	O
are	O
harder	O
to	O
clean	O
(	O
due	O
to	O
the	O
limited	O
movement	O
of	O
the	O
keys	O
and	O
their	O
multiple	O
attachment	O
points	O
)	O
but	O
also	O
less	O
likely	O
to	O
get	O
debris	O
in	O
them	O
as	O
the	O
gaps	O
between	O
the	O
keys	O
are	O
often	O
smaller	O
(	O
as	O
there	O
is	O
no	O
need	O
for	O
extra	O
room	O
to	O
allow	O
for	O
the	O
'	O
wiggle	O
 '	O
in	O
the	O
key	O
,	O
as	O
typically	O
found	O
on	O
a	O
membrane	B-Device
keyboard	I-Device
)	O
.	O
</s>
<s>
In	O
this	O
type	O
of	O
keyboard	B-Device
,	O
pressing	O
a	O
key	O
changes	O
the	O
capacitance	O
of	O
a	O
pattern	O
of	O
capacitor	O
pads	O
.	O
</s>
<s>
The	O
IBM	B-Device
Model	I-Device
F	I-Device
keyboard	I-Device
is	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
similarly	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
Topre	O
Corporation	O
design	O
for	O
key	O
switches	B-Device
uses	O
a	O
spring	O
below	O
a	O
rubber	O
dome	O
.	O
</s>
<s>
The	O
dome	O
provides	O
most	O
of	O
the	O
force	O
that	O
keeps	O
the	O
key	O
from	O
being	O
pressed	O
,	O
similar	O
to	O
a	O
membrane	B-Device
keyboard	I-Device
,	O
while	O
the	O
spring	O
helps	O
with	O
the	O
capacitive	O
action	O
.	O
</s>
<s>
Every	O
key	O
on	O
a	O
mechanical-switch	O
keyboard	B-Device
contains	O
a	O
complete	O
switch	O
underneath	O
.	O
</s>
<s>
Switches	B-Device
come	O
in	O
three	O
variants	O
:	O
"	O
linear	O
"	O
with	O
consistent	O
resistance	O
,	O
"	O
tactile	O
"	O
with	O
a	O
non-audible	O
bump	O
,	O
and	O
"	O
clicky	O
"	O
with	O
both	O
a	O
bump	O
and	O
an	O
audible	O
click	O
.	O
</s>
<s>
The	O
sound	O
can	O
be	O
altered	O
by	O
the	O
material	O
of	O
the	O
plate	O
,	O
case	O
,	O
lubrication	O
,	O
the	O
keycap	B-Device
profile	O
,	O
and	O
even	O
modifying	O
the	O
individual	O
switch	O
.	O
</s>
<s>
Mechanical	O
keyboards	B-Device
allow	O
for	O
the	O
removal	O
and	O
replacement	O
of	O
keycaps	B-Device
with	O
a	O
common	O
stem	O
type	O
.	O
</s>
<s>
Alongside	O
the	O
mechanical	O
keyboard	B-Device
switch	O
is	O
the	O
stabilizer	O
,	O
which	O
supports	O
longer	O
keys	O
such	O
as	O
the	O
"	O
spacebar	O
"	O
,	O
"	O
enter	O
"	O
,	O
"	O
backspace	O
"	O
,	O
and	O
"	O
shift	B-Device
"	O
keys	O
.	O
</s>
<s>
Although	O
these	O
are	O
not	O
as	O
diverse	O
as	O
switches	B-Device
,	O
they	O
come	O
in	O
different	O
sizes	O
.	O
</s>
<s>
These	O
different	O
sizes	O
are	O
designed	O
for	O
keyboards	B-Device
that	O
are	O
longer	O
than	O
normal	O
.	O
</s>
<s>
Similar	O
to	O
a	O
mechanical	O
keyboard	B-Device
switch	O
,	O
the	O
stabilizer	O
can	O
be	O
modified	O
to	O
alter	O
the	O
sound	O
and	O
feel	O
of	O
these	O
certain	O
keys	O
.	O
</s>
<s>
Mechanical	O
keyboards	B-Device
typically	O
have	O
a	O
longer	O
lifespan	O
than	O
membrane	O
or	O
dome-switch	O
keyboards	B-Device
.	O
</s>
<s>
A	O
major	O
producer	O
of	O
mechanical	O
switches	B-Device
is	O
Cherry	O
,	O
who	O
has	O
manufactured	O
the	O
MX	O
family	O
of	O
switches	B-Device
since	O
the	O
1980s	O
.	O
</s>
<s>
Cherry	O
's	O
color-coding	O
system	O
of	O
categorizing	O
switches	B-Device
has	O
been	O
imitated	O
by	O
other	O
mechanical	O
switch	O
manufacturers	O
,	O
such	O
as	O
Gateron	O
and	O
Kailh	O
among	O
many	O
others	O
.	O
</s>
<s>
Hot-swappable	B-Device
keyboards	B-Device
are	O
keyboards	B-Device
where	O
switches	B-Device
can	O
be	O
pulled	O
out	O
and	O
replaced	O
rather	O
than	O
requiring	O
the	O
typical	O
solder	O
connection	O
.	O
</s>
<s>
Instead	O
of	O
the	O
switch	O
being	O
soldered	O
to	O
the	O
keyboard	B-Device
's	O
PCB	O
,	O
hot-swap	B-Device
sockets	O
are	O
instead	O
soldered	O
on	O
.	O
</s>
<s>
They	O
are	O
mostly	O
used	O
by	O
keyboard	B-Device
enthusiasts	O
that	O
build	O
custom	O
keyboards	B-Device
,	O
and	O
have	O
recently	O
begun	O
being	O
adopted	O
by	O
larger	O
companies	O
on	O
production	O
keyboards	B-Device
.	O
</s>
<s>
Hot-swap	B-Device
sockets	O
typically	O
cost	O
anywhere	O
from	O
$10	O
–	O
25	O
USD	O
to	O
fill	O
a	O
complete	O
board	O
and	O
can	O
allow	O
users	O
to	O
try	O
a	O
variety	O
of	O
different	O
switches	B-Device
without	O
having	O
the	O
tools	O
or	O
knowledge	O
required	O
to	O
solder	O
electronics	O
.	O
</s>
<s>
Many	O
typists	O
prefer	O
buckling	B-Device
spring	I-Device
keyboards	B-Device
.	O
</s>
<s>
The	O
buckling	B-Device
spring	I-Device
mechanism	O
(	O
expired	O
)	O
atop	O
the	O
switch	O
is	O
responsible	O
for	O
the	O
tactile	O
and	O
aural	O
response	O
of	O
the	O
keyboard	B-Device
.	O
</s>
<s>
In	O
1993	O
,	O
two	O
years	O
after	O
spawning	O
Lexmark	O
,	O
IBM	O
transferred	O
its	O
keyboard	B-Device
operations	O
to	O
the	O
daughter	O
company	O
.	O
</s>
<s>
New	O
Model	B-Device
M	I-Device
keyboards	I-Device
continued	O
to	O
be	O
manufactured	O
for	O
IBM	O
by	O
Lexmark	O
until	O
1996	O
,	O
when	O
Unicomp	O
was	O
established	O
and	O
purchased	O
the	O
keyboard	B-Device
patents	O
and	O
tooling	O
equipment	O
to	O
continue	O
their	O
production	O
.	O
</s>
<s>
IBM	O
continued	O
to	O
make	O
Model	B-Device
M	I-Device
's	O
in	O
their	O
Scotland	O
factory	O
until	O
1999	O
.	O
</s>
<s>
Hall	O
effect	O
keyboards	B-Device
use	O
magnets	O
and	O
Hall	B-Algorithm
effect	I-Algorithm
sensors	I-Algorithm
instead	O
of	O
switches	B-Device
with	O
mechanical	O
contacts	O
.	O
</s>
<s>
Because	O
they	O
require	O
no	O
physical	O
contact	O
for	O
actuation	O
,	O
Hall-effect	O
keyboards	B-Device
are	O
extremely	O
reliable	O
and	O
can	O
accept	O
millions	O
of	O
keystrokes	O
before	O
failing	O
.	O
</s>
<s>
Because	O
a	O
magnet	O
and	O
sensor	O
are	O
required	O
for	O
each	O
key	O
,	O
as	O
well	O
as	O
custom	O
control	B-Device
electronics	O
,	O
they	O
are	O
expensive	O
to	O
manufacture	O
.	O
</s>
<s>
A	O
laser	O
projection	O
device	O
approximately	O
the	O
size	O
of	O
a	O
computer	O
mouse	O
projects	O
the	O
outline	O
of	O
keyboard	B-Device
keys	O
onto	O
a	O
flat	O
surface	O
,	O
such	O
as	O
a	O
table	O
or	O
desk	O
.	O
</s>
<s>
This	O
type	O
of	O
keyboard	B-Device
is	O
portable	O
enough	O
to	O
be	O
easily	O
used	O
with	O
PDAs	O
and	O
cellphones	O
,	O
and	O
many	O
models	O
have	O
retractable	O
cords	O
and	O
wireless	O
capabilities	O
.	O
</s>
<s>
Also	O
,	O
if	O
the	O
laser	O
malfunctions	O
,	O
the	O
whole	O
unit	O
becomes	O
useless	O
,	O
unlike	O
conventional	O
keyboards	B-Device
which	O
can	O
be	O
used	O
even	O
if	O
a	O
variety	O
of	O
parts	O
(	O
such	O
as	O
the	O
keycaps	B-Device
)	O
are	O
removed	O
.	O
</s>
<s>
This	O
type	O
of	O
keyboard	B-Device
can	O
be	O
frustrating	O
to	O
use	O
since	O
it	O
is	O
susceptible	O
to	O
errors	O
,	O
even	O
in	O
the	O
course	O
of	O
normal	O
typing	O
,	O
and	O
its	O
complete	O
lack	O
of	O
tactile	O
feedback	O
makes	O
it	O
even	O
less	O
user-friendly	O
than	O
the	O
lowest	O
quality	O
membrane	B-Device
keyboards	I-Device
.	O
</s>
<s>
Keyboards	B-Device
made	O
of	O
flexible	O
silicone	O
or	O
polyurethane	O
materials	O
can	O
roll	O
up	O
in	O
a	O
bundle	O
.	O
</s>
<s>
Tightly	O
folding	O
the	O
keyboard	B-Device
may	O
damage	O
the	O
internal	O
membrane	O
circuits	O
.	O
</s>
<s>
Roll-up	O
keyboards	B-Device
provide	O
relatively	O
little	O
tactile	O
feedback	O
,	O
and	O
silicone	O
will	O
tend	O
to	O
attract	O
dirt	O
,	O
dust	O
,	O
and	O
hair	O
.	O
</s>
<s>
Also	O
known	O
as	O
photo-optical	O
keyboard	B-Device
,	O
light	O
responsive	O
keyboard	B-Device
,	O
photo-electric	O
keyboard	B-Device
,	O
and	O
optical	O
key	O
actuation	O
detection	O
technology	O
.	O
</s>
<s>
Optical	O
keyboard	B-Device
technology	I-Device
was	O
introduced	O
in	O
1962	O
by	O
Harley	O
E	O
.	O
Kelchner	O
for	O
use	O
in	O
a	O
typewriter	O
machine	O
with	O
the	O
purpose	O
of	O
reducing	O
the	O
noise	O
generating	O
by	O
actuating	O
the	O
typewriter	O
keys	O
.	O
</s>
<s>
An	O
optical	O
keyboard	B-Device
technology	I-Device
utilizes	O
light-emitting	O
devices	O
and	O
photo	B-Algorithm
sensors	I-Algorithm
to	O
optically	O
detect	O
actuated	O
keys	O
.	O
</s>
<s>
The	O
light	O
is	O
directed	O
from	O
side	O
to	O
side	O
of	O
the	O
keyboard	B-Device
interior	O
,	O
and	O
it	O
can	O
only	O
be	O
blocked	O
by	O
the	O
actuated	O
keys	O
.	O
</s>
<s>
Most	O
optical	O
keyboards	B-Device
require	O
at	O
least	O
two	O
beams	O
(	O
most	O
commonly	O
a	O
vertical	O
beam	O
and	O
a	O
horizontal	O
beam	O
)	O
to	O
determine	O
the	O
actuated	O
key	O
.	O
</s>
<s>
Some	O
optical	O
keyboards	B-Device
use	O
a	O
special	O
key	O
structure	O
that	O
blocks	O
the	O
light	O
in	O
a	O
certain	O
pattern	O
,	O
allowing	O
only	O
one	O
beam	O
per	O
row	O
of	O
keys	O
(	O
most	O
commonly	O
a	O
horizontal	O
beam	O
)	O
.	O
</s>
<s>
The	O
mechanism	O
of	O
the	O
optical	O
keyboard	B-Device
is	O
very	O
simple	O
–	O
a	O
light	O
beam	O
is	O
sent	O
from	O
the	O
emitter	O
to	O
the	O
receiving	O
sensor	O
,	O
and	O
the	O
actuated	O
key	O
blocks	O
,	O
reflects	O
,	O
refracts	O
or	O
otherwise	O
interacts	O
with	O
the	O
beam	O
,	O
resulting	O
in	O
an	O
identified	O
key	O
.	O
</s>
<s>
Some	O
earlier	O
optical	O
keyboards	B-Device
were	O
limited	O
in	O
their	O
structure	O
and	O
required	O
special	O
casing	O
to	O
block	O
external	O
light	O
,	O
no	O
multi-key	O
functionality	O
was	O
supported	O
and	O
the	O
design	O
was	O
very	O
limited	O
to	O
a	O
thick	O
rectangular	O
case	O
.	O
</s>
<s>
The	O
advantages	O
of	O
optical	O
keyboard	B-Device
technology	I-Device
are	O
that	O
it	O
offers	O
a	O
real	O
waterproof	O
keyboard	B-Device
,	O
resilient	O
to	O
dust	O
and	O
liquids	O
;	O
and	O
it	O
uses	O
about	O
20%	O
PCB	O
volume	O
,	O
compared	O
with	O
membrane	O
or	O
dome	O
switch	O
keyboards	B-Device
,	O
significantly	O
reducing	O
electronic	O
waste	O
.	O
</s>
<s>
Additional	O
advantages	O
of	O
optical	O
keyboard	B-Device
technology	I-Device
over	O
other	O
keyboard	B-Device
technologies	I-Device
such	O
as	O
Hall	O
effect	O
,	O
laser	O
,	O
roll-up	O
,	O
and	O
transparent	O
keyboards	B-Device
lie	O
in	O
cost	O
(	O
Hall	O
effect	O
keyboard	B-Device
)	O
and	O
feel	O
–	O
optical	O
keyboard	B-Device
technology	I-Device
does	O
not	O
require	O
different	O
key	O
mechanisms	O
,	O
and	O
the	O
tactile	O
feel	O
of	O
typing	O
has	O
remained	O
the	O
same	O
for	O
over	O
60	O
years	O
.	O
</s>
<s>
The	O
specialist	O
DataHand	O
keyboard	B-Device
uses	O
optical	O
technology	O
to	O
sense	O
keypresses	O
with	O
a	O
single	O
light	O
beam	O
and	O
sensor	O
per	O
key	O
.	O
</s>
<s>
To	O
resolve	O
this	O
,	O
the	O
processor	O
in	O
a	O
keyboard	B-Device
debounces	O
the	O
keystrokes	O
,	O
by	O
averaging	O
the	O
signal	O
over	O
time	O
to	O
produce	O
one	O
"	O
confirmed	O
"	O
keystroke	O
that	O
(	O
usually	O
)	O
corresponds	O
to	O
a	O
single	O
press	O
or	O
release	O
.	O
</s>
<s>
Early	O
membrane	B-Device
keyboards	I-Device
had	O
limited	O
typing	O
speed	O
because	O
they	O
had	O
to	O
do	O
significant	O
debouncing	O
.	O
</s>
<s>
Keycaps	B-Device
are	O
used	O
on	O
full-travel	O
keyboards	B-Device
.	O
</s>
<s>
While	O
modern	O
keycaps	B-Device
are	O
typically	O
surface-printed	O
,	O
they	O
can	O
also	O
be	O
double-shot	O
molded	O
,	O
laser	O
printed	O
,	O
sublimation	O
printed	O
,	O
engraved	O
,	O
or	O
they	O
can	O
be	O
made	O
of	O
transparent	O
material	O
with	O
printed	O
paper	O
inserts	O
.	O
</s>
<s>
There	O
are	O
also	O
keycaps	B-Device
which	O
are	O
thin	O
shells	O
that	O
are	O
placed	O
over	O
key	O
bases	O
.	O
</s>
<s>
These	O
were	O
used	O
on	O
IBM	O
PC	O
keyboards	B-Device
.	O
</s>
<s>
The	O
modern	O
PC	O
keyboard	B-Device
also	O
includes	O
a	O
control	B-Device
processor	O
and	O
indicator	O
lights	O
to	O
provide	O
feedback	O
to	O
the	O
user	O
about	O
what	O
state	O
the	O
keyboard	B-Device
is	O
in	O
.	O
</s>
<s>
Depending	O
on	O
the	O
sophistication	O
of	O
the	O
controller	O
's	O
programming	O
,	O
the	O
keyboard	B-Device
may	O
also	O
offer	O
other	O
special	O
features	O
.	O
</s>
<s>
The	O
processor	O
is	O
usually	O
a	O
single	O
chip	O
8048	B-Device
microcontroller	B-Architecture
variant	O
.	O
</s>
<s>
The	O
keyboard	B-Device
switch	O
matrix	O
is	O
wired	O
to	O
its	O
inputs	O
and	O
it	O
processes	O
the	O
incoming	O
keystrokes	O
and	O
sends	O
the	O
results	O
down	O
a	O
serial	O
cable	O
(	O
the	O
keyboard	B-Device
cord	O
)	O
to	O
a	O
receiver	O
in	O
the	O
main	O
computer	O
box	O
.	O
</s>
<s>
It	O
also	O
controls	O
the	O
illumination	O
of	O
the	O
"	O
caps	B-Device
lock	I-Device
"	O
,	O
"	O
num	B-Device
lock	I-Device
"	O
and	O
"	O
scroll	B-Device
lock	I-Device
"	O
lights	O
.	O
</s>
<s>
A	O
common	O
test	O
for	O
whether	O
the	O
computer	O
has	O
crashed	O
is	O
pressing	O
the	O
"	O
caps	B-Device
lock	I-Device
"	O
key	O
.	O
</s>
<s>
The	O
keyboard	B-Device
sends	O
the	O
key	O
code	O
to	O
the	O
keyboard	B-Application
driver	I-Application
running	O
in	O
the	O
main	O
computer	O
;	O
if	O
the	O
main	O
computer	O
is	O
operating	O
,	O
it	O
commands	O
the	O
light	O
to	O
turn	O
on	O
.	O
</s>
<s>
The	O
keyboard	B-Application
driver	I-Application
also	O
tracks	O
the	O
shift	B-Device
,	O
alt	B-Device
and	O
control	B-Device
state	O
of	O
the	O
keyboard	B-Device
.	O
</s>
<s>
The	O
keyboard	B-Device
switch	O
matrix	O
is	O
often	O
drawn	O
with	O
horizontal	O
wires	O
and	O
vertical	O
wires	O
in	O
a	O
grid	O
which	O
is	O
called	O
a	O
matrix	O
circuit	O
.	O
</s>
<s>
It	O
has	O
a	O
switch	O
at	O
some	O
or	O
all	O
intersections	O
,	O
much	O
like	O
a	O
multiplexed	B-General_Concept
display	I-General_Concept
.	O
</s>
<s>
Almost	O
all	O
keyboards	B-Device
have	O
only	O
the	O
switch	O
(	O
but	O
no	O
diode	O
)	O
at	O
each	O
intersection	O
,	O
which	O
causes	O
"	O
ghost	O
keys	O
"	O
and	O
"	O
key	O
jamming	O
"	O
when	O
multiple	O
keys	O
are	O
pressed	O
(	O
rollover	B-Device
)	O
.	O
</s>
<s>
Certain	O
,	O
often	O
more	O
expensive	O
,	O
keyboards	B-Device
have	O
a	O
diode	O
between	O
each	O
intersection	O
,	O
allowing	O
the	O
keyboard	B-Device
microcontroller	B-Architecture
to	O
accurately	O
sense	O
any	O
number	O
of	O
simultaneous	O
keys	O
being	O
pressed	O
,	O
without	O
generating	O
erroneous	O
ghost	O
keys	O
.	O
</s>
<s>
Optical	B-Application
character	I-Application
recognition	I-Application
(	O
OCR	O
)	O
is	O
preferable	O
to	O
rekeying	O
for	O
converting	O
existing	O
text	O
that	O
is	O
already	O
written	O
down	O
but	O
not	O
in	O
machine-readable	O
format	O
(	O
for	O
example	O
,	O
a	O
Linotype-composed	O
book	O
from	O
the	O
1940s	O
)	O
.	O
</s>
<s>
OCR	O
technology	O
has	O
already	O
reached	O
an	O
impressive	O
state	O
(	O
for	O
example	O
,	O
Google	B-Application
Book	I-Application
Search	I-Application
)	O
and	O
promises	O
more	O
for	O
the	O
future	O
.	O
</s>
<s>
Speech	B-Application
recognition	I-Application
converts	O
speech	O
into	O
machine-readable	O
text	O
(	O
that	O
is	O
,	O
a	O
string	O
of	O
character	O
codes	O
)	O
.	O
</s>
<s>
This	O
technology	O
has	O
also	O
reached	O
an	O
advanced	O
state	O
and	O
is	O
implemented	O
in	O
various	B-General_Concept
software	I-General_Concept
products	I-General_Concept
.	O
</s>
<s>
For	O
certain	O
uses	O
(	O
e.g.	O
,	O
transcription	O
of	O
medical	O
or	O
legal	O
dictation	O
;	O
journalism	O
;	O
writing	O
essays	O
or	O
novels	O
)	O
speech	B-Application
recognition	I-Application
is	O
starting	O
to	O
replace	O
the	O
keyboard	B-Device
.	O
</s>
<s>
However	O
,	O
the	O
lack	O
of	O
privacy	O
when	O
issuing	O
voice	B-Application
commands	I-Application
and	O
dictation	O
makes	O
this	O
kind	O
of	O
input	O
unsuitable	O
for	O
many	O
environments	O
.	O
</s>
<s>
Pointing	B-Device
devices	I-Device
can	O
be	O
used	O
to	O
enter	O
text	O
or	O
characters	O
in	O
contexts	O
where	O
using	O
a	O
physical	O
keyboard	B-Device
would	O
be	O
inappropriate	O
or	O
impossible	O
.	O
</s>
<s>
Popular	O
examples	O
of	O
this	O
kind	O
of	O
input	O
are	O
Graffiti	B-Application
,	O
Dasher	B-Language
and	O
on-screen	O
virtual	B-Device
keyboards	I-Device
.	O
</s>
<s>
Unencrypted	O
Bluetooth	B-Protocol
keyboards	B-Device
are	O
known	O
to	O
be	O
vulnerable	O
to	O
signal	O
theft	O
for	O
keylogging	O
by	O
other	O
Bluetooth	B-Protocol
devices	O
in	O
range	O
.	O
</s>
<s>
Microsoft	O
wireless	O
keyboards	B-Device
2011	O
and	O
earlier	O
are	O
documented	O
to	O
have	O
this	O
vulnerability	O
.	O
</s>
<s>
Hardware	O
key	O
loggers	O
are	O
attached	O
to	O
the	O
keyboard	B-Device
cable	O
or	O
installed	O
inside	O
standard	O
keyboards	B-Device
.	O
</s>
<s>
Software	O
keyloggers	O
work	O
on	O
the	O
target	O
computer	O
's	O
operating	O
system	O
and	O
gain	O
unauthorized	O
access	O
to	O
the	O
hardware	O
,	O
hook	O
into	O
the	O
keyboard	B-Device
with	O
functions	O
provided	O
by	O
the	O
OS	O
,	O
or	O
use	O
remote	O
access	O
software	O
to	O
transmit	O
recorded	O
data	O
out	O
of	O
the	O
target	O
computer	O
to	O
a	O
remote	O
location	O
.	O
</s>
<s>
Some	O
hackers	O
also	O
use	O
wireless	O
keylogger	O
sniffers	O
to	O
collect	O
packets	O
of	O
data	O
being	O
transferred	O
from	O
a	O
wireless	O
keyboard	B-Device
and	O
its	O
receiver	O
,	O
and	O
then	O
they	O
crack	O
the	O
encryption	O
key	O
being	O
used	O
to	O
secure	O
wireless	O
communications	O
between	O
the	O
two	O
devices	O
.	O
</s>
<s>
Enabling	O
a	O
firewall	B-Application
does	O
not	O
stop	O
keyloggers	O
per	O
se	O
,	O
but	O
can	O
possibly	O
prevent	O
transmission	O
of	O
the	O
logged	O
material	O
over	O
the	O
net	O
if	O
properly	O
configured	O
.	O
</s>
<s>
Network	O
monitors	O
(	O
also	O
known	O
as	O
reverse-firewalls	O
)	O
can	O
be	O
used	O
to	O
alert	O
the	O
user	O
whenever	O
an	O
application	O
attempts	O
to	O
make	O
a	O
network	O
connection	O
.	O
</s>
<s>
Automatic	O
form-filling	O
programs	O
can	O
prevent	O
keylogging	O
entirely	O
by	O
not	O
using	O
the	O
keyboard	B-Device
at	O
all	O
.	O
</s>
<s>
Keyboards	B-Device
are	O
also	O
known	O
to	O
emit	O
electromagnetic	O
signatures	O
that	O
can	O
be	O
detected	O
using	O
special	O
spying	O
equipment	O
to	O
reconstruct	O
the	O
keys	O
pressed	O
on	O
the	O
keyboard	B-Device
.	O
</s>
<s>
The	O
use	O
of	O
any	O
keyboard	B-Device
may	O
cause	O
serious	O
injury	O
(	O
such	O
as	O
carpal	O
tunnel	O
syndrome	O
or	O
other	O
repetitive	O
strain	O
injuries	O
)	O
to	O
the	O
hands	O
,	O
wrists	O
,	O
arms	O
,	O
neck	O
or	O
back	O
.	O
</s>
<s>
When	O
typing	O
on	O
a	O
keyboard	B-Device
,	O
a	O
person	O
should	O
keep	O
the	O
shoulders	O
relaxed	O
with	O
the	O
elbows	O
at	O
the	O
side	O
,	O
with	O
the	O
keyboard	B-Device
and	O
mouse	O
positioned	O
so	O
that	O
reaching	O
is	O
not	O
necessary	O
.	O
</s>
<s>
The	O
chair	O
height	O
and	O
keyboard	B-Device
tray	O
should	O
be	O
adjusted	O
so	O
that	O
the	O
wrists	O
are	O
straight	O
,	O
and	O
the	O
wrists	O
should	O
not	O
be	O
rested	O
on	O
sharp	O
table	O
edges	O
.	O
</s>
<s>
Some	O
adaptive	O
technology	O
ranging	O
from	O
special	O
keyboards	B-Device
,	O
mouse	O
replacements	O
and	O
pen	O
tablet	O
interfaces	O
to	O
speech	B-Application
recognition	I-Application
software	I-Application
can	O
reduce	O
the	O
risk	O
of	O
injury	O
.	O
</s>
<s>
By	O
using	O
a	O
touchpad	B-Application
or	O
a	O
stylus	O
pen	O
with	O
a	O
graphic	O
tablet	O
,	O
in	O
place	O
of	O
a	O
mouse	O
,	O
one	O
can	O
lessen	O
the	O
repetitive	O
strain	O
on	O
the	O
arms	O
and	O
hands	O
.	O
</s>
