<s>
A	O
vacuum	B-General_Concept
fluorescent	I-General_Concept
display	I-General_Concept
(	O
VFD	O
)	O
is	O
a	O
display	B-Device
device	I-Device
once	O
commonly	O
used	O
on	O
consumer	O
electronics	O
equipment	O
such	O
as	O
video	O
cassette	B-Device
recorders	O
,	O
car	O
radios	O
,	O
and	O
microwave	O
ovens	O
.	O
</s>
<s>
A	O
VFD	O
operates	O
on	O
the	O
principle	O
of	O
cathodoluminescence	O
,	O
roughly	O
similar	O
to	O
a	O
cathode	B-Device
ray	I-Device
tube	I-Device
,	O
but	O
operating	O
at	O
much	O
lower	O
voltages	O
.	O
</s>
<s>
In	O
fact	O
,	O
each	O
tube	O
in	O
a	O
VFD	O
is	O
a	O
triode	O
vacuum	B-General_Concept
tube	O
because	O
it	O
also	O
has	O
a	O
mesh	O
control	O
grid	O
.	O
</s>
<s>
Unlike	O
liquid	B-Device
crystal	I-Device
displays	I-Device
,	O
a	O
VFD	O
emits	O
very	O
bright	O
light	O
with	O
high	O
contrast	O
and	O
can	O
support	O
display	O
elements	O
of	O
various	O
colors	O
.	O
</s>
<s>
VFDs	O
can	O
display	O
seven-segment	B-General_Concept
numerals	O
,	O
multi-segment	O
alpha-numeric	O
characters	O
or	O
can	O
be	O
made	O
in	O
a	O
dot-matrix	O
to	O
display	O
different	O
alphanumeric	O
characters	O
and	O
symbols	O
.	O
</s>
<s>
The	O
first	O
multi-segment	O
VFD	O
was	O
a	O
1967	O
Japanese	O
single-digit	O
,	O
seven-segment	B-General_Concept
device	O
.	O
</s>
<s>
The	O
device	O
consists	O
of	O
a	O
hot	O
cathode	O
(	O
filaments	O
)	O
,	O
grids	O
and	O
anodes	O
(	O
phosphor	O
)	O
encased	O
in	O
a	O
glass	O
envelope	O
under	O
a	O
high	O
vacuum	B-General_Concept
condition	O
.	O
</s>
<s>
The	O
cathode	O
is	O
made	O
up	O
of	O
fine	O
tungsten	B-Application
wires	O
,	O
coated	O
by	O
alkaline	O
earth	O
metal	O
oxides	O
(	O
barium	O
,	O
strontium	O
and	O
calcium	O
oxides	O
)	O
,	O
which	O
emit	O
electrons	O
when	O
heated	O
to	O
650°C	O
by	O
an	O
electric	O
current	O
.	O
</s>
<s>
Unlike	O
the	O
orange-glowing	O
cathodes	O
of	O
traditional	O
vacuum	B-General_Concept
tubes	O
,	O
VFD	O
cathodes	O
are	O
efficient	O
emitters	O
at	O
much	O
lower	O
temperatures	O
,	O
and	O
are	O
therefore	O
essentially	O
invisible	O
.	O
</s>
<s>
The	O
anode	O
consists	O
of	O
a	O
glass	O
plate	O
with	O
electrically	O
conductive	O
traces	O
(	O
each	O
trace	O
is	O
connected	O
to	O
a	O
single	O
indicator	O
segment	O
)	O
,	O
which	O
is	O
coated	O
with	O
an	O
insulator	O
,	O
which	O
is	O
then	O
partially	O
etched	O
to	O
create	O
holes	O
which	O
are	O
then	O
filled	O
with	O
a	O
conductor	O
like	O
graphite	B-Application
,	O
which	O
in	O
turn	O
is	O
coated	O
with	O
phosphor	O
.	O
</s>
<s>
The	O
cathode	O
wire	O
to	O
which	O
the	O
oxides	O
are	O
applied	O
is	O
made	O
of	O
tungsten	B-Application
or	O
ruthenium-tungsten	O
alloy	O
.	O
</s>
<s>
The	O
oxides	O
in	O
the	O
cathodes	O
are	O
not	O
stable	O
in	O
air	O
,	O
so	O
they	O
are	O
applied	O
to	O
the	O
cathode	O
as	O
carbonates	O
,	O
the	O
cathodes	O
are	O
assembled	O
into	O
the	O
VFD	O
,	O
and	O
the	O
cathodes	O
are	O
heated	O
by	O
passing	O
a	O
current	O
through	O
them	O
while	O
inside	O
the	O
vacuum	B-General_Concept
of	O
the	O
VFD	O
to	O
convert	O
the	O
carbonates	O
into	O
oxides	O
.	O
</s>
<s>
The	O
principle	O
of	O
operation	O
is	O
identical	O
to	O
that	O
of	O
a	O
vacuum	B-General_Concept
tube	O
triode	O
.	O
</s>
<s>
This	O
allows	O
the	O
displays	O
to	O
be	O
organized	O
as	O
multiplexed	B-General_Concept
displays	I-General_Concept
where	O
the	O
multiple	O
grids	O
and	O
plates	O
form	O
a	O
matrix	O
,	O
minimizing	O
the	O
number	O
of	O
signal	O
pins	O
required	O
.	O
</s>
<s>
One	O
by	O
one	O
,	O
the	O
microprocessor	B-Architecture
driving	O
the	O
display	O
enables	O
a	O
digit	O
by	O
placing	O
a	O
positive	O
voltage	O
on	O
that	O
digit	O
's	O
grid	O
and	O
then	O
placing	O
a	O
positive	O
voltage	O
on	O
the	O
appropriate	O
plates	O
.	O
</s>
<s>
The	O
microprocessor	B-Architecture
cycles	O
through	O
illuminating	O
the	O
digits	O
in	O
this	O
way	O
at	O
a	O
rate	O
high	O
enough	O
to	O
create	O
the	O
illusion	O
of	O
all	O
digits	O
glowing	O
at	O
once	O
via	O
persistence	O
of	O
vision	O
.	O
</s>
<s>
Besides	O
brightness	O
,	O
VFDs	O
have	O
the	O
advantages	O
of	O
being	O
rugged	O
,	O
inexpensive	O
,	O
and	O
easily	O
configured	O
to	O
display	O
a	O
wide	O
variety	O
of	O
customized	O
messages	O
,	O
and	O
unlike	O
LCDs	B-Device
,	O
VFDs	O
are	O
not	O
limited	O
by	O
the	O
response	O
time	O
of	O
rearranging	O
liquid	B-Device
crystals	I-Device
and	O
are	O
thus	O
able	O
to	O
function	O
normally	O
in	O
cold	O
,	O
even	O
sub-zero	O
,	O
temperatures	O
,	O
making	O
them	O
ideal	O
for	O
outdoor	O
devices	O
in	O
cold	O
climates	O
.	O
</s>
<s>
Early	O
on	O
,	O
the	O
main	O
disadvantage	O
of	O
such	O
displays	O
was	O
their	O
use	O
of	O
significantly	O
more	O
power	O
(	O
0.2	O
watts	O
)	O
than	O
a	O
simple	O
LCD	B-Device
.	O
</s>
<s>
During	O
the	O
1980s	O
,	O
this	O
display	O
began	O
to	O
be	O
used	O
in	O
automobiles	O
,	O
especially	O
where	O
car	O
makers	O
were	O
experimenting	O
with	O
digital	B-Device
displays	I-Device
for	O
vehicle	O
instruments	O
such	O
as	O
speedometers	O
and	O
odometers	O
.	O
</s>
<s>
A	O
good	O
example	O
of	O
these	O
were	O
the	O
high-end	O
Subaru	O
cars	O
made	O
in	O
the	O
early	O
1980s	O
(	O
referred	O
to	O
by	O
Subaru	O
enthusiasts	O
as	O
a	O
digi-dash	O
,	O
or	O
digital	O
dashboard	B-Protocol
)	O
.	O
</s>
<s>
The	O
Renault	O
Espace	O
and	O
older	O
models	O
of	O
Scenic	O
used	O
VFD	O
panels	O
to	O
show	O
all	O
functions	O
on	O
the	O
dashboard	B-Protocol
including	O
the	O
radio	O
and	O
multi	O
message	O
panel	O
.	O
</s>
<s>
This	O
technology	O
was	O
also	O
used	O
from	O
1979	O
to	O
the	O
mid-1980s	O
in	O
portable	B-Application
electronic	I-Application
game	I-Application
units	O
.	O
</s>
<s>
These	O
games	O
featured	O
bright	O
,	O
clear	O
displays	O
but	O
the	O
size	O
of	O
the	O
largest	O
vacuum	B-General_Concept
tubes	O
that	O
could	O
be	O
manufactured	O
inexpensively	O
kept	O
the	O
size	O
of	O
the	O
displays	O
quite	O
small	O
,	O
often	O
requiring	O
the	O
use	O
of	O
magnifying	O
Fresnel	O
lenses	O
.	O
</s>
<s>
LCD	B-Application
games	I-Application
could	O
be	O
manufactured	O
for	O
a	O
fraction	O
of	O
the	O
price	O
,	O
did	O
not	O
require	O
frequent	O
changes	O
of	O
batteries	O
(	O
or	O
AC	O
adapters	O
)	O
and	O
were	O
much	O
more	O
portable	O
.	O
</s>
<s>
Since	O
the	O
late	O
1990s	O
,	O
backlit	O
color	O
active-matrix	O
LCD	B-Device
displays	I-Device
have	O
been	O
able	O
to	O
cheaply	O
reproduce	O
arbitrary	O
images	O
in	O
any	O
color	O
,	O
a	O
marked	O
advantage	O
over	O
fixed-color	O
,	O
fixed-character	O
VFDs	O
.	O
</s>
<s>
From	O
the	O
mid-1980s	O
onwards	O
,	O
VFDs	O
were	O
used	O
for	O
applications	O
requiring	O
smaller	O
displays	O
with	O
high	O
brightness	O
specifications	O
,	O
though	O
now	O
the	O
adoption	O
of	O
high-brightness	O
organic	B-Device
light-emitting	I-Device
diodes	I-Device
(	O
OLEDs	B-Device
)	O
is	O
pushing	O
VFDs	O
out	O
of	O
these	O
markets	O
.	O
</s>
<s>
Vacuum	B-General_Concept
fluorescent	I-General_Concept
displays	I-General_Concept
were	O
once	O
commonly	O
used	O
as	O
floor	O
indicators	O
for	O
elevators	O
by	O
Otis	O
Elevator	O
Company	O
worldwide	O
and	O
Montgomery	O
Elevator	O
Company	O
in	O
North	O
America	O
(	O
the	O
former	O
from	O
the	O
early	O
1980s	O
to	O
the	O
mid-2000s	O
in	O
the	O
form	O
of	O
(	O
usually	O
two	O
)	O
16-segment	B-General_Concept
displays	I-General_Concept
,	O
and	O
the	O
latter	O
from	O
the	O
mid	O
1980s	O
to	O
the	O
mid	O
1990s	O
in	O
the	O
form	O
of	O
(	O
usually	O
3	O
)	O
10x14	O
dot-matrix	B-General_Concept
displays	I-General_Concept
)	O
.	O
</s>
<s>
Of	O
the	O
three	O
prevalent	O
display	B-Device
technologies	I-Device
–	O
VFD	O
,	O
LCD	B-Device
,	O
and	O
LED	O
–	O
the	O
VFD	O
was	O
the	O
first	O
to	O
be	O
developed	O
.	O
</s>
<s>
Later	O
,	O
LCDs	B-Device
displaced	O
LEDs	O
,	O
offering	O
even	O
lower	O
power	O
requirements	O
.	O
</s>
<s>
The	O
1967	O
Japanese	O
single	O
digit	O
seven	B-General_Concept
segment	I-General_Concept
display	I-General_Concept
in	O
terms	O
of	O
anode	O
was	O
more	O
like	O
the	O
Philips	O
DM70	O
/	O
DM71	O
Magic	O
Eye	O
as	O
the	O
DM160	O
has	O
a	O
spiral	O
wire	O
anode	O
.	O
</s>
<s>
The	O
Japanese	O
seven	O
segment	O
VFD	O
meant	O
that	O
no	O
patent	O
royalties	O
needed	O
to	O
be	O
paid	O
on	O
desk	O
calculator	O
displays	O
as	O
would	O
have	O
been	O
the	O
case	O
using	O
Nixies	B-Application
or	O
Panaplex	O
neon	O
digits	O
.	O
</s>
