<s>
A	O
cathode-ray	B-Device
tube	I-Device
(	O
CRT	O
)	O
is	O
a	O
vacuum	B-General_Concept
tube	O
containing	O
one	O
or	O
more	O
electron	O
guns	O
,	O
which	O
emit	O
electron	O
beams	O
that	O
are	O
manipulated	O
to	O
display	O
images	O
on	O
a	O
phosphorescent	O
screen	O
.	O
</s>
<s>
The	O
images	O
may	O
represent	O
electrical	O
waveforms	O
(	O
oscilloscope	O
)	O
,	O
pictures	O
(	O
television	O
set	O
,	O
computer	B-Device
monitor	I-Device
)	O
,	O
radar	B-Application
targets	O
,	O
or	O
other	O
phenomena	O
.	O
</s>
<s>
A	O
CRT	O
on	O
a	O
television	O
set	O
is	O
commonly	O
called	O
a	O
picture	B-Device
tube	I-Device
.	O
</s>
<s>
CRTs	O
have	O
also	O
been	O
used	B-General_Concept
as	I-General_Concept
memory	I-General_Concept
devices	I-General_Concept
,	O
in	O
which	O
case	O
the	O
screen	O
is	O
not	O
intended	O
to	O
be	O
visible	O
to	O
an	O
observer	O
.	O
</s>
<s>
In	O
CRT	O
television	O
sets	O
and	O
computer	B-Device
monitors	I-Device
,	O
the	O
entire	O
front	O
area	O
of	O
the	O
tube	O
is	O
scanned	O
repeatedly	O
and	O
systematically	O
in	O
a	O
fixed	O
pattern	O
called	O
a	O
raster	B-Algorithm
.	O
</s>
<s>
In	O
color	O
devices	O
,	O
an	O
image	O
is	O
produced	O
by	O
controlling	O
the	O
intensity	O
of	O
each	O
of	O
three	O
electron	O
beams	O
,	O
one	O
for	O
each	O
additive	O
primary	O
color	O
(	O
red	O
,	O
green	O
,	O
and	O
blue	O
)	O
with	O
a	O
video	B-Application
signal	I-Application
as	O
a	O
reference	O
.	O
</s>
<s>
In	O
modern	O
CRT	B-Device
monitors	I-Device
and	O
televisions	O
the	O
beams	O
are	O
bent	O
by	O
magnetic	O
deflection	O
,	O
using	O
a	O
deflection	O
yoke	O
.	O
</s>
<s>
The	O
face	O
is	O
typically	O
made	O
of	O
thick	O
lead	O
glass	O
or	O
special	O
barium-strontium	O
glass	O
to	O
be	O
shatter-resistant	O
and	O
to	O
block	O
most	O
X-ray	B-Library
emissions	O
.	O
</s>
<s>
CRTs	O
make	O
up	O
most	O
of	O
the	O
weight	O
of	O
CRT	O
TVs	O
and	O
computer	B-Device
monitors	I-Device
.	O
</s>
<s>
Since	O
the	O
mid-late	O
2000	O
's	O
,	O
CRTs	O
have	O
been	O
superseded	O
by	O
flat-panel	B-General_Concept
display	I-General_Concept
technologies	O
such	O
as	O
LCD	B-Device
,	O
plasma	O
display	O
,	O
and	O
OLED	B-Device
displays	I-Device
which	O
are	O
cheaper	O
to	O
manufacture	O
and	O
run	O
,	O
as	O
well	O
as	O
significantly	O
lighter	O
and	O
less	O
bulky	O
.	O
</s>
<s>
Flat-panel	B-General_Concept
displays	I-General_Concept
can	O
also	O
be	O
made	O
in	O
very	O
large	O
sizes	O
whereas	O
to	O
was	O
about	O
the	O
largest	O
size	O
of	O
a	O
CRT	O
.	O
</s>
<s>
The	O
earliest	O
version	O
of	O
the	O
CRT	O
was	O
known	O
as	O
the	O
"	O
Braun	B-Device
tube	I-Device
"	O
,	O
invented	O
by	O
the	O
German	O
physicist	O
Ferdinand	O
Braun	O
in	O
1897	O
.	O
</s>
<s>
In	O
1908	O
,	O
Alan	O
Archibald	O
Campbell-Swinton	O
,	O
fellow	O
of	O
the	O
Royal	O
Society	O
(	O
UK	O
)	O
,	O
published	O
a	O
letter	O
in	O
the	O
scientific	O
journal	O
Nature	O
,	O
in	O
which	O
he	O
described	O
how	O
"	O
distant	O
electric	O
vision	O
"	O
could	O
be	O
achieved	O
by	O
using	O
a	O
cathode-ray	B-Device
tube	I-Device
(	O
or	O
"	O
Braun	O
"	O
tube	O
)	O
as	O
both	O
a	O
transmitting	O
and	O
receiving	O
device	O
.	O
</s>
<s>
The	O
first	O
cathode-ray	B-Device
tube	I-Device
to	O
use	O
a	O
hot	O
cathode	O
was	O
developed	O
by	O
John	O
Bertrand	O
Johnson	O
(	O
who	O
gave	O
his	O
name	O
to	O
the	O
term	O
Johnson	O
noise	O
)	O
and	O
Harry	O
Weiner	O
Weinhart	O
of	O
Western	O
Electric	O
,	O
and	O
became	O
a	O
commercial	O
product	O
in	O
1922	O
.	O
</s>
<s>
By	O
1928	O
,	O
he	O
was	O
the	O
first	O
to	O
transmit	O
human	O
faces	O
in	O
half-tones	O
on	O
a	O
CRT	B-Device
display	I-Device
.	O
</s>
<s>
RCA	O
was	O
granted	O
a	O
trademark	O
for	O
the	O
term	O
(	O
for	O
its	O
cathode-ray	B-Device
tube	I-Device
)	O
in	O
1932	O
;	O
it	O
voluntarily	O
released	O
the	O
term	O
to	O
the	O
public	O
domain	O
in	O
1950	O
.	O
</s>
<s>
The	O
first	O
commercially	O
made	O
electronic	O
television	O
sets	O
with	O
cathode-ray	B-Device
tubes	I-Device
were	O
manufactured	O
by	O
Telefunken	O
in	O
Germany	O
in	O
1934	O
.	O
</s>
<s>
In	O
1947	O
,	O
the	O
cathode-ray	B-Application
tube	I-Application
amusement	I-Application
device	I-Application
,	O
the	O
earliest	O
known	O
interactive	B-General_Concept
electronic	O
game	O
as	O
well	O
as	O
the	O
first	O
to	O
incorporate	O
a	O
cathode-ray	B-Device
tube	I-Device
screen	O
,	O
was	O
created	O
.	O
</s>
<s>
It	O
was	O
a	O
CRT	O
in	O
a	O
flat-panel	B-General_Concept
display	I-General_Concept
format	O
with	O
a	O
single	O
electron	O
gun	O
.	O
</s>
<s>
It	O
was	O
also	O
envisioned	O
as	O
a	O
head-up	B-Application
display	I-Application
in	O
aircraft	O
.	O
</s>
<s>
1968	O
marks	O
the	O
release	O
of	O
Sony	O
Trinitron	O
brand	O
with	O
the	O
model	O
KV-1310	O
,	O
which	O
was	O
based	O
on	O
Aperture	B-General_Concept
Grille	I-General_Concept
technology	O
.	O
</s>
<s>
In	O
1987	O
,	O
flat-screen	O
CRTs	O
were	O
developed	O
by	O
Zenith	O
for	O
computer	B-Device
monitors	I-Device
,	O
reducing	O
reflections	O
and	O
helping	O
increase	O
image	O
contrast	O
and	O
brightness	O
.	O
</s>
<s>
Such	O
CRTs	O
were	O
expensive	O
,	O
which	O
limited	O
their	O
use	O
to	O
computer	B-Device
monitors	I-Device
.	O
</s>
<s>
In	O
the	O
mid-2000s	O
,	O
Canon	O
and	O
Sony	O
presented	O
the	O
surface-conduction	B-General_Concept
electron-emitter	I-General_Concept
display	I-General_Concept
and	O
field-emission	B-General_Concept
displays	I-General_Concept
,	O
respectively	O
.	O
</s>
<s>
They	O
both	O
were	O
flat-panel	B-General_Concept
displays	I-General_Concept
that	O
had	O
one	O
(	O
SED	O
)	O
or	O
several	O
(	O
FED	O
)	O
electron	O
emitters	O
per	O
subpixel	O
in	O
place	O
of	O
electron	O
guns	O
.	O
</s>
<s>
They	O
were	O
never	O
put	O
into	O
mass	O
production	O
as	O
LCD	B-Device
technology	O
was	O
significantly	O
cheaper	O
,	O
eliminating	O
the	O
market	O
for	O
such	O
displays	O
.	O
</s>
<s>
Worldwide	O
sales	O
of	O
CRT	O
computer	B-Device
monitors	I-Device
peaked	O
in	O
2000	O
,	O
at	O
90	O
million	O
units	O
,	O
while	O
those	O
of	O
CRT	O
TVs	O
peaked	O
in	O
2005	O
at	O
130	O
million	O
units	O
.	O
</s>
<s>
Beginning	O
in	O
the	O
late	O
90s	O
to	O
the	O
early	O
2000s	O
,	O
CRTs	O
began	O
to	O
be	O
replaced	O
with	O
LCDs	B-Device
,	O
starting	O
first	O
with	O
computer	B-Device
monitors	I-Device
smaller	O
than	O
15	O
inches	O
in	O
size	O
,	O
largely	O
because	O
of	O
their	O
lower	O
bulk	O
.	O
</s>
<s>
Among	O
the	O
first	O
manufacturers	O
to	O
stop	O
CRT	O
production	O
was	O
Hitachi	O
in	O
2001	O
,	O
followed	O
by	O
Sony	O
in	O
Japan	O
in	O
2004	O
,	O
Flat-panel	B-General_Concept
displays	I-General_Concept
dropped	O
in	O
price	O
and	O
started	O
significantly	O
displacing	O
cathode-ray	B-Device
tubes	I-Device
in	O
the	O
2000s	O
.	O
</s>
<s>
LCD	B-Device
monitor	O
sales	O
began	O
exceeding	O
those	O
of	O
CRTs	O
in	O
2003	O
–	O
2004	O
and	O
LCD	B-Device
TV	O
sales	O
started	O
exceeding	O
those	O
of	O
CRTs	O
in	O
some	O
markets	O
in	O
2005	O
.	O
</s>
<s>
Despite	O
being	O
a	O
mainstay	O
of	O
display	O
technology	O
for	O
decades	O
,	O
CRT-based	O
computer	B-Device
monitors	I-Device
and	O
televisions	O
are	O
now	O
virtually	O
a	O
dead	O
technology	O
.	O
</s>
<s>
Demand	O
for	O
CRT	B-Device
screens	I-Device
dropped	O
in	O
the	O
late	O
2000s	O
.	O
</s>
<s>
Despite	O
efforts	O
from	O
Samsung	O
and	O
LG	O
to	O
make	O
CRTs	O
competitive	O
with	O
their	O
LCD	B-Device
and	O
plasma	O
counterparts	O
,	O
offering	O
slimmer	O
and	O
cheaper	O
models	O
to	O
compete	O
with	O
similarly	O
sized	O
and	O
more	O
expensive	O
LCDs	B-Device
,	O
CRTs	O
eventually	O
became	O
obsolete	O
and	O
were	O
relegated	O
to	O
developing	O
markets	O
once	O
LCDs	B-Device
fell	O
in	O
price	O
,	O
with	O
their	O
lower	O
bulk	O
,	O
weight	O
and	O
ability	O
to	O
be	O
wall	O
mounted	O
coming	O
as	O
pluses	O
.	O
</s>
<s>
Planes	O
such	O
as	O
the	O
Boeing	O
747-400	O
and	O
the	O
Airbus	O
A320	O
used	O
CRT	O
instruments	O
in	O
their	O
glass	B-Device
cockpits	I-Device
instead	O
of	O
mechanical	O
instruments	O
.	O
</s>
<s>
Airlines	O
such	O
as	O
Lufthansa	O
still	O
use	O
CRT	O
technology	O
,	O
which	O
also	O
uses	O
floppy	B-Device
disks	I-Device
for	O
navigation	O
updates	O
.	O
</s>
<s>
Some	O
games	O
are	O
impossible	O
to	O
play	O
without	O
CRT	B-Device
display	I-Device
hardware	O
,	O
and	O
some	O
games	O
play	O
better	O
.	O
</s>
<s>
CRTs	O
refresh	O
faster	O
than	O
LCDs	B-Device
,	O
because	O
they	O
use	O
interlaced	O
lines	O
.	O
</s>
<s>
CRTs	O
are	O
able	O
to	O
correctly	O
display	O
certain	O
oddball	O
resolutions	B-Algorithm
,	O
such	O
as	O
the	O
256x224	O
resolution	O
of	O
the	O
Nintendo	O
Entertainment	O
System	O
(	O
NES	O
)	O
.	O
</s>
<s>
Light	B-Device
guns	I-Device
only	O
work	O
on	O
CRTs	O
because	O
they	O
depend	O
on	O
the	O
progressive	O
timing	O
properties	O
of	O
CRTs	O
.	O
</s>
<s>
The	O
glass	O
,	O
known	O
as	O
CRT	O
glass	O
or	O
TV	O
glass	O
,	O
needs	O
special	O
properties	O
to	O
shield	O
against	O
x-rays	B-Library
while	O
providing	O
adequate	O
light	O
transmission	O
in	O
the	O
screen	O
or	O
being	O
very	O
electrically	O
insulating	O
in	O
the	O
funnel	O
and	O
neck	O
.	O
</s>
<s>
Standard	O
transmittances	O
for	O
Color	O
CRT	B-Device
screens	I-Device
are	O
86%	O
,	O
73%	O
,	O
57%	O
,	O
46%	O
,	O
42%	O
and	O
30%	O
.	O
</s>
<s>
The	O
radius	O
(	O
curvature	O
)	O
of	O
screens	O
has	O
increased	O
(	O
grown	O
less	O
curved	O
)	O
over	O
time	O
,	O
from	O
30	O
to	O
68	O
inches	O
,	O
ultimately	O
evolving	O
into	O
completely	O
flat	B-General_Concept
screens	I-General_Concept
,	O
reducing	O
reflections	O
.	O
</s>
<s>
The	O
thickness	O
of	O
both	O
curved	O
and	O
flat	B-General_Concept
screens	I-General_Concept
gradually	O
increases	O
from	O
the	O
center	O
outwards	O
,	O
and	O
with	O
it	O
,	O
transmittance	O
is	O
gradually	O
reduced	O
.	O
</s>
<s>
The	O
funnel	O
and	O
the	O
neck	O
are	O
made	O
of	O
leaded	O
potash-soda	O
glass	O
or	O
lead	O
silicate	O
glass	O
formulation	O
to	O
shield	O
against	O
x-rays	B-Library
generated	O
by	O
high	O
voltage	O
electrons	O
as	O
they	O
decelerate	O
after	O
striking	O
a	O
target	O
,	O
such	O
as	O
the	O
phosphor	O
screen	O
or	O
shadow	B-General_Concept
mask	I-General_Concept
of	O
a	O
color	O
CRT	O
.	O
</s>
<s>
The	O
amount	O
of	O
x-rays	B-Library
emitted	O
by	O
a	O
CRT	O
can	O
also	O
lowered	O
by	O
reducing	O
the	O
brightness	O
of	O
the	O
image	O
.	O
</s>
<s>
Leaded	O
glass	O
is	O
used	O
because	O
it	O
is	O
inexpensive	O
,	O
while	O
also	O
shielding	O
heavily	O
against	O
x-rays	B-Library
,	O
although	O
some	O
funnels	O
may	O
also	O
contain	O
barium	O
.	O
</s>
<s>
The	O
screen	O
is	O
usually	O
instead	O
made	O
out	O
of	O
a	O
special	O
lead-free	O
silicate	O
glass	O
formulation	O
with	O
barium	O
and	O
strontium	O
to	O
shield	O
against	O
x-rays	B-Library
.	O
</s>
<s>
The	O
lead	O
in	O
the	O
glass	O
causes	O
it	O
to	O
brown	O
(	O
darken	O
)	O
with	O
use	O
due	O
to	O
x-rays	B-Library
,	O
usually	O
the	O
CRT	O
cathode	O
wears	O
out	O
due	O
to	O
cathode	O
poisoning	O
before	O
browning	O
becomes	O
apparent	O
.	O
</s>
<s>
The	O
glass	O
formulation	O
determines	O
the	O
highest	O
possible	O
anode	O
voltage	O
and	O
hence	O
the	O
maximum	O
possible	O
CRT	B-Device
screen	I-Device
size	O
.	O
</s>
<s>
The	O
stability	O
provided	O
by	O
the	O
coating	O
solved	O
problems	O
inherent	O
to	O
early	O
power	O
supply	O
designs	O
,	O
as	O
they	O
used	O
vacuum	B-General_Concept
tubes	O
.	O
</s>
<s>
Usual	O
deflection	O
angles	O
were	O
90°	O
for	O
computer	B-Device
monitor	I-Device
CRTs	O
and	O
small	O
CRTs	O
and	O
110°	O
which	O
was	O
the	O
standard	O
in	O
larger	O
TV	O
CRTs	O
,	O
with	O
120	O
or	O
125°	O
being	O
used	O
in	O
slim	O
CRTs	O
made	O
since	O
2001	O
–	O
2005	O
in	O
an	O
attempt	O
to	O
compete	O
with	O
LCD	B-Device
TVs	O
.	O
</s>
<s>
The	O
size	O
of	O
the	O
screen	O
is	O
the	O
viewable	O
image	B-Algorithm
size	I-Algorithm
plus	O
its	O
black	O
edges	O
which	O
are	O
not	O
coated	O
with	O
phosphor	O
.	O
</s>
<s>
The	O
anode	O
is	O
used	O
to	O
accelerate	O
the	O
electrons	O
towards	O
the	O
screen	O
and	O
also	O
collects	O
the	O
secondary	O
electrons	O
that	O
are	O
emitted	O
by	O
the	O
phosphor	O
particles	O
in	O
the	O
vacuum	B-General_Concept
of	O
the	O
CRT	O
.	O
</s>
<s>
X-rays	B-Library
may	O
leak	O
through	O
the	O
anode	O
button	O
,	O
although	O
that	O
may	O
not	O
be	O
the	O
case	O
in	O
newer	O
CRTs	O
starting	O
from	O
the	O
late	O
1970s	O
to	O
early	O
1980s	O
,	O
thanks	O
to	O
a	O
new	O
button	O
and	O
clip	O
design	O
.	O
</s>
<s>
The	O
button	O
may	O
consist	O
of	O
a	O
set	O
of	O
3	O
nested	O
cups	O
,	O
with	O
the	O
outermost	O
cup	O
being	O
made	O
of	O
a	O
Nickel	O
–	O
Chromium	O
–	O
Iron	O
alloy	O
containing	O
40	O
to	O
49%	O
of	O
Nickel	O
and	O
3	O
to	O
6%	O
of	O
Chromium	O
to	O
make	O
the	O
button	O
easy	O
to	O
fuse	O
to	O
the	O
funnel	O
glass	O
,	O
with	O
a	O
first	O
inner	O
cup	O
made	O
of	O
thick	O
inexpensive	O
iron	O
to	O
shield	O
against	O
x-rays	B-Library
,	O
and	O
with	O
the	O
second	O
innermost	O
cup	O
also	O
being	O
made	O
of	O
iron	O
or	O
any	O
other	O
electrically	O
conductive	O
metal	O
to	O
connect	O
to	O
the	O
clip	O
.	O
</s>
<s>
Alternatively	O
,	O
the	O
x-ray	B-Library
shielding	O
may	O
instead	O
be	O
built	O
into	O
the	O
clip	O
.	O
</s>
<s>
The	O
main	O
secondary	O
winding	O
supplies	O
the	O
voltage	O
multiplier	O
with	O
voltage	O
pulses	O
to	O
ultimately	O
supply	O
the	O
CRT	O
with	O
the	O
high	O
anode	O
voltage	O
it	O
uses	O
,	O
while	O
the	O
remaining	O
windings	O
supply	O
the	O
CRT	O
's	O
filament	O
voltage	O
,	O
keying	O
pulses	O
,	O
focus	O
voltage	O
and	O
voltages	O
derived	O
from	O
the	O
scan	O
raster	B-Algorithm
.	O
</s>
<s>
The	O
design	O
of	O
the	O
high	O
voltage	O
power	O
supply	O
in	O
a	O
product	O
using	O
a	O
CRT	O
has	O
an	O
influence	O
in	O
the	O
amount	O
of	O
x-rays	B-Library
emitted	O
by	O
the	O
CRT	O
.	O
</s>
<s>
The	O
amount	O
of	O
emitted	O
x-rays	B-Library
increases	O
with	O
both	O
higher	O
voltages	O
and	O
currents	O
.	O
</s>
<s>
If	O
the	O
product	O
such	O
as	O
a	O
TV	O
set	O
uses	O
an	O
unregulated	O
high	O
voltage	O
power	O
supply	O
,	O
meaning	O
that	O
anode	O
and	O
focus	O
voltage	O
go	O
down	O
with	O
increasing	O
electron	O
current	O
when	O
displaying	O
a	O
bright	O
image	O
,	O
the	O
amount	O
of	O
emitted	O
x-rays	B-Library
is	O
as	O
its	O
highest	O
when	O
the	O
CRT	O
is	O
displaying	O
a	O
moderately	O
bright	O
images	O
,	O
since	O
when	O
displaying	O
dark	O
or	O
bright	O
images	O
,	O
the	O
higher	O
anode	O
voltage	O
counteracts	O
the	O
lower	O
electron	O
beam	O
current	O
and	O
vice	O
versa	O
respectively	O
.	O
</s>
<s>
The	O
high	O
voltage	O
regulator	O
and	O
rectifier	O
vacuum	B-General_Concept
tubes	O
in	O
some	O
old	O
CRT	O
TV	O
sets	O
may	O
also	O
emit	O
x-rays	B-Library
.	O
</s>
<s>
Activation	O
occurs	O
during	O
evacuation	O
of	O
(	O
at	O
the	O
same	O
time	O
a	O
vacuum	B-General_Concept
is	O
formed	O
in	O
)	O
the	O
CRT	O
.	O
</s>
<s>
Since	O
it	O
is	O
a	O
hot	O
cathode	O
,	O
it	O
is	O
prone	O
to	O
cathode	O
poisoning	O
,	O
which	O
is	O
the	O
formation	O
of	O
a	O
positive	O
ion	O
layer	O
that	O
prevents	O
the	O
cathode	O
from	O
emitting	O
electrons	O
,	O
reducing	O
image	O
brightness	O
significantly	O
or	O
completely	O
and	O
causing	O
focus	O
and	O
intensity	O
to	O
be	O
affected	O
by	O
the	O
frequency	O
of	O
the	O
video	B-Application
signal	I-Application
preventing	O
detailed	O
images	O
from	O
being	O
displayed	O
by	O
the	O
CRT	O
.	O
</s>
<s>
Normally	O
,	O
only	O
a	O
part	O
of	O
the	O
cathode	O
emits	O
electrons	O
unless	O
the	O
CRT	B-Device
displays	I-Device
images	O
with	O
parts	O
that	O
are	O
at	O
full	O
image	O
brightness	O
;	O
only	O
the	O
parts	O
at	O
full	O
brightness	O
cause	O
all	O
of	O
the	O
cathode	O
to	O
emit	O
electrons	O
.	O
</s>
<s>
When	O
only	O
the	O
center	O
of	O
the	O
cathode	O
is	O
worn	O
,	O
the	O
CRT	O
may	O
light	O
brightly	O
those	O
parts	O
of	O
images	O
that	O
have	O
full	O
image	O
brightness	O
but	O
not	O
show	O
darker	O
parts	O
of	O
images	O
at	O
all	O
,	O
in	O
such	O
a	O
case	O
the	O
CRT	B-Device
displays	I-Device
a	O
poor	O
gamma	O
characteristic	O
.	O
</s>
<s>
TV	O
sets	O
and	O
computer	B-Device
monitors	I-Device
that	O
incorporate	O
CRTs	O
need	O
a	O
DC	O
restoration	O
circuit	O
to	O
provide	O
a	O
video	B-Application
signal	I-Application
to	O
the	O
CRT	O
with	O
a	O
DC	O
component	O
,	O
restoring	O
the	O
original	O
brightness	O
of	O
different	O
parts	O
of	O
the	O
image	O
.	O
</s>
<s>
The	O
amplifier	O
's	O
capabilities	O
limit	O
the	O
resolution	O
,	O
refresh	O
rate	O
and	O
contrast	O
ratio	O
of	O
the	O
CRT	O
,	O
as	O
the	O
amplifier	O
needs	O
to	O
provide	O
high	O
bandwidth	O
and	O
voltage	O
variations	O
at	O
the	O
same	O
time	O
;	O
higher	O
resolutions	B-Algorithm
and	O
refresh	O
rates	O
need	O
higher	O
bandwidths	O
(	O
speed	O
at	O
which	O
voltage	O
can	O
be	O
varied	O
and	O
thus	O
switching	O
between	O
black	O
and	O
white	O
)	O
and	O
higher	O
contrast	O
ratios	O
need	O
higher	O
voltage	O
variations	O
or	O
amplitude	O
for	O
lower	O
black	O
and	O
higher	O
white	O
levels	O
.	O
</s>
<s>
A	O
CRT	O
needs	O
two	O
deflection	O
circuits	O
:	O
a	O
horizontal	O
and	O
a	O
vertical	O
circuit	O
,	O
which	O
are	O
similar	O
except	O
that	O
the	O
horizontal	O
circuit	O
runs	O
at	O
a	O
much	O
higher	O
frequency	O
(	O
a	O
Horizontal	B-General_Concept
scan	I-General_Concept
rate	I-General_Concept
)	O
of	O
15	O
to	O
240kHz	O
depending	O
on	O
the	O
refresh	O
rate	O
of	O
the	O
CRT	O
and	O
the	O
number	O
of	O
horizontal	O
lines	O
to	O
be	O
drawn	O
(	O
the	O
vertical	O
resolution	O
of	O
the	O
CRT	O
)	O
.	O
</s>
<s>
Burn-in	B-General_Concept
is	O
when	O
images	O
are	O
physically	O
"	O
burned	O
"	O
into	O
the	O
screen	O
of	O
the	O
CRT	O
;	O
this	O
occurs	O
due	O
to	O
degradation	O
of	O
the	O
phosphors	O
due	O
to	O
prolonged	O
electron	O
bombardment	O
of	O
the	O
phosphors	O
,	O
and	O
happens	O
when	O
a	O
fixed	O
image	O
or	O
logo	O
is	O
left	O
for	O
too	O
long	O
on	O
the	O
screen	O
,	O
causing	O
it	O
to	O
appear	O
as	O
a	O
"	O
ghost	O
"	O
image	O
or	O
,	O
in	O
severe	O
cases	O
,	O
also	O
when	O
the	O
CRT	O
is	O
off	O
.	O
</s>
<s>
To	O
counter	O
this	O
,	O
screensavers	B-General_Concept
were	O
used	O
in	O
computers	O
to	O
minimize	O
burn-in	B-General_Concept
.	O
</s>
<s>
Burn-in	B-General_Concept
is	O
not	O
exclusive	O
to	O
CRTs	O
,	O
as	O
it	O
also	O
happens	O
to	O
plasma	O
displays	O
and	O
OLED	B-Device
displays	I-Device
.	O
</s>
<s>
CRTs	O
are	O
evacuated	O
or	O
exhausted	O
(	O
a	O
vacuum	B-General_Concept
is	O
formed	O
)	O
inside	O
an	O
oven	O
at	O
approx	O
.	O
</s>
<s>
The	O
heating	O
and	O
cooling	O
are	O
done	O
gradually	O
to	O
avoid	O
inducing	O
stress	O
,	O
stiffening	O
and	O
possibly	O
cracking	O
the	O
glass	O
;	O
the	O
oven	O
heats	O
the	O
gases	O
inside	O
the	O
CRT	O
,	O
increasing	O
the	O
speed	O
of	O
the	O
gas	O
molecules	O
which	O
increases	O
the	O
chances	O
of	O
them	O
getting	O
drawn	O
out	O
by	O
the	O
vacuum	B-General_Concept
pump	O
.	O
</s>
<s>
Formerly	O
mercury	O
vacuum	B-General_Concept
pumps	O
were	O
also	O
used	O
.	O
</s>
<s>
After	O
baking	O
,	O
the	O
CRT	O
is	O
disconnected	O
(	O
"	O
sealed	O
or	O
tipped	O
off	O
"	O
)	O
from	O
the	O
vacuum	B-General_Concept
pump	O
.	O
</s>
<s>
Partial	O
loss	O
of	O
vacuum	B-General_Concept
in	O
a	O
CRT	O
can	O
result	O
in	O
a	O
hazy	O
image	O
,	O
blue	O
glowing	O
in	O
the	O
neck	O
of	O
the	O
CRT	O
,	O
flashovers	O
,	O
loss	O
of	O
cathode	O
emission	O
or	O
focusing	O
problems	O
.	O
</s>
<s>
The	O
vacuum	B-General_Concept
inside	O
of	O
a	O
CRT	O
causes	O
atmospheric	O
pressure	O
to	O
exert	O
(	O
in	O
a	O
27-inch	O
CRT	O
)	O
a	O
pressure	O
of	O
in	O
total	O
.	O
</s>
<s>
Phosphors	O
in	O
CRTs	O
emit	O
secondary	O
electrons	O
due	O
to	O
them	O
being	O
inside	O
the	O
vacuum	B-General_Concept
of	O
the	O
CRT	O
.	O
</s>
<s>
Phosphors	O
were	O
classified	O
according	O
to	O
color	O
,	O
persistence	B-Device
,	O
luminance	O
rise	O
and	O
fall	O
curves	O
,	O
color	O
depending	O
on	O
anode	O
voltage	O
(	O
for	O
phosphors	O
used	O
in	O
penetration	O
CRTs	O
)	O
,	O
Intended	O
use	O
,	O
chemical	O
composition	O
,	O
safety	O
,	O
sensitivity	O
to	O
burn-in	B-General_Concept
,	O
and	O
secondary	O
emission	O
properties	O
.	O
</s>
<s>
The	O
standard	O
prioritizes	O
accurate	O
color	O
reproduction	O
,	O
which	O
was	O
made	O
difficult	O
by	O
the	O
different	O
phosphors	O
and	O
color	O
spaces	O
used	O
in	O
the	O
NTSC	O
and	O
PAL	B-Language
color	O
systems	O
.	O
</s>
<s>
PAL	B-Language
TV	O
sets	O
have	O
subjectively	O
better	O
color	O
reproduction	O
due	O
to	O
the	O
use	O
of	O
saturated	O
green	O
phosphors	O
,	O
which	O
have	O
relatively	O
long	O
decay	O
times	O
that	O
are	O
tolerated	O
in	O
PAL	B-Language
since	O
there	O
is	O
more	O
time	O
in	O
PAL	B-Language
for	O
phosphors	O
to	O
decay	O
,	O
due	O
to	O
its	O
lower	O
framerate	O
.	O
</s>
<s>
The	O
brightness	O
,	O
color	O
,	O
and	O
persistence	B-Device
of	O
the	O
illumination	O
depends	O
upon	O
the	O
type	O
of	O
phosphor	O
used	O
on	O
the	O
CRT	B-Device
screen	I-Device
.	O
</s>
<s>
For	O
visual	O
observation	O
of	O
brief	O
transient	O
events	O
,	O
a	O
long	O
persistence	B-Device
phosphor	O
may	O
be	O
desirable	O
.	O
</s>
<s>
For	O
events	O
which	O
are	O
fast	O
and	O
repetitive	O
,	O
or	O
high	O
frequency	O
,	O
a	O
short-persistence	O
phosphor	O
is	O
generally	O
preferable	O
.	O
</s>
<s>
The	O
phosphor	O
persistence	B-Device
must	O
be	O
low	O
enough	O
to	O
avoid	O
smearing	O
or	O
ghosting	O
artifacts	O
at	O
high	O
refresh	O
rates	O
.	O
</s>
<s>
Doming	O
is	O
a	O
phenomenon	O
found	O
on	O
some	O
CRT	O
televisions	O
in	O
which	O
parts	O
of	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
become	O
heated	O
.	O
</s>
<s>
As	O
the	O
electron	O
beam	O
hits	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
in	O
these	O
areas	O
it	O
heats	O
unevenly	O
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
warps	O
due	O
to	O
the	O
heat	O
differences	O
,	O
which	O
causes	O
the	O
electron	O
gun	O
to	O
hit	O
the	O
wrong	O
colored	O
phosphors	O
and	O
incorrect	O
colors	O
to	O
be	O
displayed	O
in	O
the	O
affected	O
area	O
.	O
</s>
<s>
Thermal	O
expansion	O
causes	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
to	O
expand	O
by	O
around	O
100	O
microns	O
.	O
</s>
<s>
During	O
normal	O
operation	O
,	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
is	O
heated	O
to	O
around	O
80	O
–	O
90°C	O
.	O
</s>
<s>
Bright	O
areas	O
of	O
images	O
heat	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
more	O
than	O
dark	O
areas	O
,	O
leading	O
to	O
uneven	O
heating	O
of	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
and	O
warping	O
(	O
blooming	O
)	O
due	O
to	O
thermal	O
expansion	O
caused	O
by	O
heating	O
by	O
increased	O
electron	O
beam	O
current	O
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
is	O
usually	O
made	O
of	O
steel	O
but	O
it	O
can	O
be	O
made	O
of	O
Invar	O
(	O
a	O
low-thermal	O
expansion	O
Nickel-Iron	O
alloy	O
)	O
as	O
it	O
withstands	O
two	O
to	O
three	O
times	O
more	O
current	O
than	O
conventional	O
masks	O
without	O
noticeable	O
warping	O
,	O
while	O
making	O
higher	O
resolution	O
CRTs	O
easier	O
to	O
achieve	O
.	O
</s>
<s>
Coatings	O
that	O
dissipate	O
heat	O
may	O
be	O
applied	O
on	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
to	O
limit	O
blooming	O
in	O
a	O
process	O
called	O
blackening	O
.	O
</s>
<s>
Bimetal	O
springs	O
may	O
be	O
used	O
in	O
CRTs	O
used	O
in	O
TVs	O
to	O
compensate	O
for	O
warping	O
that	O
occurs	O
as	O
the	O
electron	O
beam	O
heats	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
causing	O
thermal	O
expansion	O
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
is	O
installed	O
to	O
the	O
screen	O
using	O
metal	O
pieces	O
or	O
a	O
rail	O
or	O
frame	O
that	O
is	O
fused	O
to	O
the	O
funnel	O
or	O
the	O
screen	O
glass	O
respectively	O
,	O
holding	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
in	O
tension	O
to	O
minimize	O
warping	O
(	O
if	O
the	O
mask	O
is	O
flat	O
,	O
used	O
in	O
flat-screen	O
CRT	O
computer	B-Device
monitors	I-Device
)	O
and	O
allowing	O
for	O
higher	O
image	O
brightness	O
and	O
contrast	O
.	O
</s>
<s>
Aperture	B-General_Concept
grille	I-General_Concept
screens	O
are	O
brighter	O
since	O
they	O
allow	O
more	O
electrons	O
through	O
,	O
but	O
they	O
require	O
support	O
wires	O
.	O
</s>
<s>
Color	O
CRTs	O
need	O
higher	O
anode	O
voltages	O
than	O
monochrome	O
CRTs	O
to	O
achieve	O
the	O
same	O
brightness	O
since	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
blocks	O
most	O
of	O
the	O
electron	O
beam	O
.	O
</s>
<s>
Slot	O
masks	O
and	O
specially	O
Aperture	B-General_Concept
grilles	I-General_Concept
do	O
not	O
block	O
as	O
many	O
electrons	O
resulting	O
in	O
a	O
brighter	O
image	O
for	O
a	O
given	O
anode	O
voltage	O
,	O
but	O
aperture	B-General_Concept
grille	I-General_Concept
CRTs	O
are	O
heavier	O
.	O
</s>
<s>
Shadow	B-General_Concept
masks	I-General_Concept
block	O
80	O
–	O
85%	O
of	O
the	O
electron	O
beam	O
while	O
Aperture	B-General_Concept
grilles	I-General_Concept
allow	O
more	O
electrons	O
to	O
pass	O
through	O
.	O
</s>
<s>
Higher	O
anode	O
voltages	O
and	O
electron	O
beam	O
currents	O
also	O
mean	O
higher	O
amounts	O
of	O
x-rays	B-Library
and	O
heat	O
generation	O
since	O
the	O
electrons	O
have	O
a	O
higher	O
speed	O
and	O
energy	O
.	O
</s>
<s>
Leaded	O
glass	O
and	O
special	O
barium-strontium	O
glass	O
are	O
used	O
to	O
block	O
most	O
x-ray	B-Library
emissions	O
.	O
</s>
<s>
The	O
weight	O
of	O
the	O
CRT	O
,	O
which	O
originates	O
from	O
the	O
thick	O
glass	O
needed	O
to	O
safely	O
sustain	O
a	O
vacuum	B-General_Concept
,	O
imposes	O
a	O
practical	O
limit	O
on	O
the	O
size	O
of	O
a	O
CRT	O
.	O
</s>
<s>
The	O
43-inch	O
Sony	O
PVM-4300	O
CRT	B-Device
monitor	I-Device
weighs	O
.	O
</s>
<s>
For	O
comparison	O
,	O
a	O
32-inch	O
flat	B-General_Concept
panel	I-General_Concept
TV	I-General_Concept
only	O
weighs	O
approx	O
.	O
</s>
<s>
and	O
a	O
19-inch	O
flat	B-General_Concept
panel	I-General_Concept
TV	I-General_Concept
weighs	O
.	O
</s>
<s>
Shadow	B-General_Concept
masks	I-General_Concept
become	O
more	O
difficult	O
to	O
make	O
with	O
increasing	O
resolution	O
and	O
size	O
.	O
</s>
<s>
At	O
high	O
deflection	O
angles	O
,	O
resolutions	B-Algorithm
and	O
refresh	O
rates	O
(	O
since	O
higher	O
resolutions	B-Algorithm
and	O
refresh	O
rates	O
require	O
significantly	O
higher	O
frequencies	O
to	O
be	O
applied	O
to	O
the	O
horizontal	O
deflection	O
coils	O
)	O
,	O
the	O
deflection	O
yoke	O
starts	O
to	O
produce	O
large	O
amounts	O
of	O
heat	O
,	O
due	O
to	O
the	O
need	O
to	O
move	O
the	O
electron	O
beam	O
at	O
a	O
higher	O
angle	O
,	O
which	O
in	O
turn	O
requires	O
exponentially	O
larger	O
amounts	O
of	O
power	O
.	O
</s>
<s>
This	O
normally	O
makes	O
CRTs	O
that	O
go	O
beyond	O
certain	O
deflection	O
angles	O
,	O
resolutions	B-Algorithm
and	O
refresh	O
rates	O
impractical	O
,	O
since	O
the	O
coils	O
would	O
generate	O
too	O
much	O
heat	O
due	O
to	O
resistance	O
caused	O
by	O
the	O
skin	O
effect	O
,	O
surface	O
and	O
eddy	O
current	O
losses	O
,	O
and/or	O
possibly	O
causing	O
the	O
glass	O
underneath	O
the	O
coil	O
to	O
become	O
conductive	O
(	O
as	O
the	O
electrical	O
conductivity	O
of	O
glass	O
decreases	O
with	O
increasing	O
temperature	O
)	O
.	O
</s>
<s>
OLED	B-Device
advantages	O
over	O
CRT	O
:	O
Lower	O
bulk	O
,	O
similar	O
color	O
reproduction	O
,	O
higher	O
contrast	O
ratios	O
,	O
similar	O
refresh	O
rates	O
(	O
over	O
60Hz	O
,	O
up	O
to	O
120Hz	O
)	O
except	O
for	O
computer	B-Device
monitors	I-Device
.	O
</s>
<s>
LCDs	B-Device
that	O
can	O
compete	O
with	O
OLED	B-Device
(	O
Dual	O
Layer	O
,	O
and	O
mini-LED	O
LCDs	B-Device
)	O
are	O
not	O
available	O
in	O
high	O
refresh	O
rates	O
,	O
although	O
quantum	O
dot	O
LCDs	B-Device
(	O
QLEDs	O
)	O
are	O
available	O
in	O
high	O
refresh	O
rates	O
(	O
up	O
to	O
144Hz	O
)	O
and	O
are	O
competitive	O
in	O
color	O
reproduction	O
with	O
OLEDs	B-Device
.	O
</s>
<s>
CRT	B-Device
monitors	I-Device
can	O
still	O
outperform	O
LCD	B-Device
and	O
OLED	B-Device
monitors	O
in	O
input	O
lag	O
,	O
as	O
there	O
is	O
no	O
signal	O
processing	O
between	O
the	O
CRT	O
and	O
the	O
display	O
connector	O
of	O
the	O
monitor	O
,	O
since	O
CRT	B-Device
monitors	I-Device
often	O
use	O
VGA	O
which	O
provides	O
an	O
analog	O
signal	O
that	O
can	O
be	O
fed	O
to	O
a	O
CRT	O
directly	O
.	O
</s>
<s>
Video	O
cards	O
designed	O
for	O
use	O
with	O
CRTs	O
may	O
have	O
a	O
RAMDAC	B-Device
to	O
generate	O
the	O
analog	O
signals	O
needed	O
by	O
the	O
CRT	O
.	O
</s>
<s>
Also	O
,	O
CRT	B-Device
monitors	I-Device
are	O
often	O
capable	O
of	O
displaying	O
sharp	O
images	O
at	O
several	O
resolutions	B-Algorithm
,	O
an	O
ability	O
known	O
as	O
multisyncing	B-General_Concept
.	O
</s>
<s>
CRTs	O
tend	O
to	O
be	O
more	O
durable	O
than	O
their	O
flat	B-General_Concept
panel	I-General_Concept
counterparts	O
,	O
though	O
specialised	O
LCDs	B-Device
that	O
have	O
similar	O
durability	O
also	O
exist	O
.	O
</s>
<s>
CRTs	O
were	O
produced	O
in	O
two	O
major	O
categories	O
,	O
picture	B-Device
tubes	I-Device
and	O
display	O
tubes	O
.	O
</s>
<s>
Picture	B-Device
tubes	I-Device
were	O
used	O
in	O
TVs	O
while	O
display	O
tubes	O
were	O
used	O
in	O
computer	B-Device
monitors	I-Device
.	O
</s>
<s>
Picture	B-Device
tube	I-Device
CRTs	O
have	O
overscan	O
,	O
meaning	O
the	O
actual	O
edges	O
of	O
the	O
image	O
are	O
not	O
shown	O
;	O
this	O
is	O
deliberate	O
to	O
allow	O
for	O
adjustment	O
variations	O
between	O
CRT	O
TVs	O
,	O
preventing	O
the	O
ragged	O
edges	O
(	O
due	O
to	O
blooming	O
)	O
of	O
the	O
image	O
from	O
being	O
shown	O
on	O
screen	O
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
may	O
have	O
grooves	O
that	O
reflect	O
away	O
the	O
electrons	O
that	O
do	O
not	O
hit	O
the	O
screen	O
due	O
to	O
overscan	O
.	O
</s>
<s>
Color	O
picture	B-Device
tubes	I-Device
used	O
in	O
TVs	O
were	O
also	O
known	O
as	O
CPTs	O
.	O
</s>
<s>
CRTs	O
are	O
also	O
sometimes	O
called	O
Braun	B-Device
tubes	I-Device
.	O
</s>
<s>
If	O
the	O
CRT	O
is	O
a	O
black	O
and	O
white	O
(	O
B&W	O
or	O
monochrome	O
)	O
CRT	O
,	O
there	O
is	O
a	O
single	O
electron	O
gun	O
in	O
the	O
neck	O
and	O
the	O
funnel	O
is	O
coated	B-General_Concept
on	I-General_Concept
the	I-General_Concept
inside	I-General_Concept
with	I-General_Concept
aluminum	I-General_Concept
that	O
has	O
been	O
applied	O
by	O
evaporation	O
;	O
the	O
aluminum	O
is	O
evaporated	O
in	O
a	O
vacuum	B-General_Concept
and	O
allowed	O
to	O
condense	O
on	O
the	O
inside	O
of	O
the	O
CRT	O
.	O
</s>
<s>
The	O
screen	O
has	O
a	O
single	O
uniform	O
phosphor	O
coating	O
and	O
no	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
technically	O
having	O
no	O
resolution	O
limit	O
.	O
</s>
<s>
They	O
are	O
packed	O
together	O
in	O
stripes	O
(	O
as	O
in	O
aperture	B-General_Concept
grille	I-General_Concept
designs	O
)	O
or	O
clusters	O
called	O
"	B-General_Concept
triads	I-General_Concept
"	I-General_Concept
(	O
as	O
in	O
shadow	B-General_Concept
mask	I-General_Concept
CRTs	O
)	O
.	O
</s>
<s>
A	O
shadow	B-General_Concept
mask	I-General_Concept
tube	O
uses	O
a	O
metal	O
plate	O
with	O
tiny	O
holes	O
,	O
typically	O
in	O
a	O
delta	O
configuration	O
,	O
placed	O
so	O
that	O
the	O
electron	O
beam	O
only	O
illuminates	O
the	O
correct	O
phosphors	O
on	O
the	O
face	O
of	O
the	O
tube	O
;	O
blocking	O
all	O
other	O
electrons	O
.	O
</s>
<s>
Shadow	B-General_Concept
masks	I-General_Concept
that	O
use	O
slots	O
instead	O
of	O
holes	O
are	O
known	O
as	O
slot	O
masks	O
.	O
</s>
<s>
Another	O
type	O
of	O
color	O
CRT	O
(	O
Trinitron	O
)	O
uses	O
an	O
aperture	B-General_Concept
grille	I-General_Concept
of	O
tensioned	O
vertical	O
wires	O
to	O
achieve	O
the	O
same	O
result	O
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
has	O
a	O
single	O
hole	O
for	O
each	O
triad	B-General_Concept
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
is	O
usually	O
1/2	O
inch	O
behind	O
the	O
screen	O
.	O
</s>
<s>
Trinitron	O
CRTs	O
were	O
different	O
from	O
other	O
color	O
CRTs	O
in	O
that	O
they	O
had	O
a	O
single	O
electron	O
gun	O
with	O
three	O
cathodes	O
,	O
an	O
aperture	B-General_Concept
grille	I-General_Concept
which	O
lets	O
more	O
electrons	O
through	O
,	O
increasing	O
image	O
brightness	O
(	O
since	O
the	O
aperture	B-General_Concept
grille	I-General_Concept
does	O
not	O
block	O
as	O
many	O
electrons	O
)	O
,	O
and	O
a	O
vertically	O
cylindrical	O
screen	O
,	O
rather	O
than	O
a	O
curved	O
screen	O
.	O
</s>
<s>
The	O
funnel	O
is	O
coated	O
with	O
aquadag	O
on	O
both	O
sides	O
while	O
the	O
screen	O
has	O
a	O
separate	O
aluminum	O
coating	O
applied	O
in	O
a	O
vacuum	B-General_Concept
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
absorbs	O
or	O
reflects	O
electrons	O
that	O
would	O
otherwise	O
strike	O
the	O
wrong	O
phosphor	O
dots	O
,	O
causing	O
color	O
purity	O
issues	O
(	O
discoloration	O
of	O
images	O
)	O
;	O
in	O
other	O
words	O
,	O
when	O
set	O
up	O
correctly	O
,	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
helps	O
ensure	O
color	O
purity	O
.	O
</s>
<s>
When	O
the	O
electrons	O
strike	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
they	O
release	O
their	O
energy	O
as	O
heat	O
and	O
x-rays	B-Library
.	O
</s>
<s>
If	O
the	O
electrons	O
have	O
too	O
much	O
energy	O
due	O
to	O
an	O
anode	O
voltage	O
that	O
is	O
too	O
high	O
for	O
example	O
,	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
can	O
warp	O
due	O
to	O
the	O
heat	O
,	O
which	O
can	O
also	O
happen	O
during	O
the	O
Lehr	O
baking	O
at	O
approx	O
.	O
</s>
<s>
Shadow	B-General_Concept
masks	I-General_Concept
were	O
replaced	O
in	O
TVs	O
by	O
slot	O
masks	O
in	O
the	O
1970s	O
,	O
since	O
slot	O
masks	O
let	O
more	O
electrons	O
through	O
,	O
increasing	O
image	O
brightness	O
.	O
</s>
<s>
Shadow	B-General_Concept
masks	I-General_Concept
may	O
be	O
connected	O
electrically	O
to	O
the	O
anode	O
of	O
the	O
CRT	O
.	O
</s>
<s>
CRT	O
PC	B-Device
monitors	I-Device
usually	O
use	O
shadow	B-General_Concept
masks	I-General_Concept
,	O
except	O
for	O
Sony	O
's	O
Trinitron	O
,	O
Mitsubishi	O
's	O
Diamondtron	O
and	O
NEC	O
's	O
Cromaclear	B-General_Concept
;	O
Trinitron	O
and	O
Diamondtron	O
use	O
aperture	B-General_Concept
grilles	I-General_Concept
while	O
Cromaclear	B-General_Concept
uses	O
a	O
slot	O
mask	O
.	O
</s>
<s>
Some	O
shadow	B-General_Concept
mask	I-General_Concept
CRTs	O
have	O
color	O
phosphors	O
that	O
are	O
smaller	O
in	O
diameter	O
than	O
the	O
electron	O
beams	O
used	O
to	O
light	O
them	O
,	O
with	O
the	O
intention	O
being	O
to	O
cover	O
the	O
entire	O
phosphor	O
,	O
increasing	O
image	O
brightness	O
.	O
</s>
<s>
Shadow	B-General_Concept
masks	I-General_Concept
may	O
be	O
pressed	O
into	O
a	O
curved	O
shape	O
.	O
</s>
<s>
This	O
is	O
also	O
made	O
necessary	O
by	O
warping	O
of	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
.	O
</s>
<s>
At	O
high	B-Algorithm
resolutions	I-Algorithm
and	O
refresh	O
rates	O
,	O
phosphors	O
only	O
receive	O
a	O
very	O
small	O
amount	O
of	O
energy	O
,	O
limiting	O
image	O
brightness	O
.	O
</s>
<s>
Then	O
carbon	O
was	O
applied	O
to	O
the	O
remaining	O
areas	O
of	O
the	O
screen	O
while	O
exposing	O
the	O
entire	O
screen	O
to	O
light	O
to	O
create	O
the	O
black	O
matrix	O
,	O
and	O
a	O
fixing	O
process	O
using	O
an	O
aqueous	O
polymer	B-Language
solution	O
was	O
applied	O
to	O
the	O
screen	O
to	O
make	O
the	O
phosphors	O
and	O
black	O
matrix	O
resistant	O
to	O
water	O
.	O
</s>
<s>
The	O
phosphors	O
are	O
applied	O
using	O
photolithography	B-Algorithm
.	O
</s>
<s>
Removable	O
shadow	B-General_Concept
masks	I-General_Concept
with	O
spring-loaded	O
clips	O
are	O
used	O
as	O
photomasks	O
.	O
</s>
<s>
Alternatively	O
,	O
the	O
phosphors	O
may	O
be	O
applied	O
in	O
a	O
vacuum	B-General_Concept
chamber	O
by	O
evaporating	O
them	O
and	O
allowing	O
them	O
to	O
condense	O
on	O
the	O
screen	O
,	O
creating	O
a	O
very	O
uniform	O
coating	O
.	O
</s>
<s>
Poor	O
exposure	O
due	O
to	O
insufficient	O
light	O
leads	O
to	O
poor	O
phosphor	O
adhesion	O
to	O
the	O
screen	O
,	O
which	O
limits	O
the	O
maximum	O
resolution	O
of	O
a	O
CRT	O
,	O
as	O
the	O
smaller	O
phosphor	O
dots	O
required	O
for	O
higher	O
resolutions	B-Algorithm
cannot	O
receive	O
as	O
much	O
light	O
due	O
to	O
their	O
smaller	O
size	O
.	O
</s>
<s>
After	O
the	O
screen	O
is	O
coated	O
with	O
phosphor	O
and	O
aluminum	O
and	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
installed	O
onto	O
it	O
the	O
screen	O
is	O
bonded	O
to	O
the	O
funnel	O
using	O
a	O
glass	O
frit	O
that	O
may	O
contain	O
65	O
to	O
88%	O
of	O
lead	O
oxide	O
by	O
weight	O
.	O
</s>
<s>
The	O
frit	O
may	O
be	O
applied	O
as	O
a	O
paste	O
consisting	O
of	O
frit	O
particles	O
suspended	O
in	O
amyl	O
acetate	O
or	O
in	O
a	O
polymer	B-Language
with	O
an	O
alkyl	O
methacrylate	O
monomer	O
together	O
with	O
an	O
organic	O
solvent	O
to	O
dissolve	O
the	O
polymer	B-Language
and	O
monomer	O
.	O
</s>
<s>
Frit	O
is	O
used	O
in	O
color	O
CRTs	O
to	O
prevent	O
deformation	O
of	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
and	O
screen	O
during	O
the	O
fusing	O
process	O
.	O
</s>
<s>
The	O
Lehr	O
bake	O
consists	O
of	O
several	O
successive	O
steps	O
that	O
heat	O
and	O
then	O
cool	O
the	O
CRT	O
gradually	O
until	O
it	O
reaches	O
a	O
temperature	O
of	O
435	O
to	O
475°C	O
(	O
other	O
sources	O
may	O
state	O
different	O
temperatures	O
,	O
such	O
as	O
440°C	O
)	O
After	O
the	O
Lehr	O
bake	O
,	O
the	O
CRT	O
is	O
flushed	O
with	O
air	O
or	O
nitrogen	O
to	O
remove	O
contaminants	O
,	O
the	O
electron	O
gun	O
is	O
inserted	O
and	O
sealed	O
into	O
the	O
neck	O
of	O
the	O
CRT	O
,	O
and	O
a	O
vacuum	B-General_Concept
is	O
formed	O
on	O
the	O
CRT	O
.	O
</s>
<s>
Due	O
to	O
limitations	O
in	O
the	O
dimensional	O
precision	O
with	O
which	O
CRTs	O
can	O
be	O
manufactured	O
economically	O
,	O
it	O
has	O
not	O
been	O
practically	O
possible	O
to	O
build	O
color	O
CRTs	O
in	O
which	O
three	O
electron	O
beams	O
could	O
be	O
aligned	O
to	O
hit	O
phosphors	O
of	O
respective	O
color	O
in	O
acceptable	O
coordination	O
,	O
solely	O
on	O
the	O
basis	O
of	O
the	O
geometric	O
configuration	O
of	O
the	O
electron	O
gun	O
axes	O
and	O
gun	O
aperture	O
positions	O
,	O
shadow	B-General_Concept
mask	I-General_Concept
apertures	O
,	O
etc	O
.	O
</s>
<s>
The	O
shadow	B-General_Concept
mask	I-General_Concept
ensures	O
that	O
one	O
beam	O
will	O
only	O
hit	O
spots	O
of	O
certain	O
colors	O
of	O
phosphors	O
,	O
but	O
minute	O
variations	O
in	O
physical	O
alignment	O
of	O
the	O
internal	O
parts	O
among	O
individual	O
CRTs	O
will	O
cause	O
variations	O
in	O
the	O
exact	O
alignment	O
of	O
the	O
beams	O
through	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
allowing	O
some	O
electrons	O
from	O
,	O
for	O
example	O
,	O
the	O
red	O
beam	O
to	O
hit	O
,	O
say	O
,	O
blue	O
phosphors	O
,	O
unless	O
some	O
individual	O
compensation	O
is	O
made	O
for	O
the	O
variance	O
among	O
individual	O
tubes	O
.	O
</s>
<s>
Firstly	O
,	O
for	O
correct	O
color	O
rendering	O
it	O
is	O
necessary	O
that	O
regardless	O
of	O
where	O
the	O
beams	O
are	O
deflected	O
on	O
the	O
screen	O
,	O
all	O
three	O
hit	O
the	O
same	O
spot	O
(	O
and	O
nominally	O
pass	O
through	O
the	O
same	O
hole	O
or	O
slot	O
)	O
on	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
.	O
</s>
<s>
Dynamic	O
convergence	O
is	O
necessary	O
because	O
the	O
front	O
of	O
the	O
CRT	O
and	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
are	O
not	O
spherical	O
,	O
compensating	O
for	O
electron	O
beam	O
defocusing	O
and	O
astigmatism	O
.	O
</s>
<s>
The	O
fact	O
that	O
the	O
CRT	B-Device
screen	I-Device
is	O
not	O
spherical	O
leads	O
to	O
geometry	O
problems	O
which	O
may	O
be	O
corrected	O
using	O
a	O
circuit	O
.	O
</s>
<s>
This	O
type	O
of	O
convergence	O
is	O
necessary	O
due	O
to	O
the	O
high	O
deflection	O
angles	O
and	O
flat	B-General_Concept
screens	I-General_Concept
of	O
many	O
CRT	O
computer	B-Device
monitors	I-Device
.	O
</s>
<s>
90°	O
deflection	O
angle	O
CRTs	O
may	O
use	O
"	O
self-convergence	O
"	O
without	O
dynamic	O
convergence	O
,	O
which	O
together	O
with	O
the	O
in-line	O
triad	B-General_Concept
arrangement	O
,	O
eliminates	O
the	O
need	O
for	O
separate	O
convergence	O
coils	O
and	O
related	O
circuitry	O
,	O
reducing	O
costs	O
.	O
</s>
<s>
The	O
same	O
techniques	O
(	O
and	O
major	O
circuit	O
components	O
)	O
also	O
make	O
possible	O
the	O
adjustment	O
of	O
display	O
image	O
rotation	O
,	O
skew	O
,	O
and	O
other	O
complex	O
raster	B-Algorithm
geometry	O
parameters	O
through	O
electronics	O
under	O
user	O
control	O
.	O
</s>
<s>
There	O
are	O
4	O
sets	O
of	O
rings	O
,	O
one	O
to	O
adjust	O
RGB	O
convergence	O
,	O
a	O
second	O
to	O
adjust	O
Red	O
and	O
Blue	O
convergence	O
,	O
a	O
third	O
to	O
adjust	O
vertical	O
raster	B-Algorithm
shift	O
,	O
and	O
a	O
fourth	O
to	O
adjust	O
purity	O
.	O
</s>
<s>
The	O
vertical	O
raster	B-Algorithm
shift	O
adjusts	O
the	O
straightness	O
of	O
the	O
scan	B-Algorithm
line	I-Algorithm
.	O
</s>
<s>
In	O
early	O
color	O
CRTs	O
,	O
the	O
holes	O
in	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
became	O
progressively	O
smaller	O
as	O
they	O
extended	O
outwards	O
from	O
the	O
center	O
of	O
the	O
screen	O
,	O
to	O
aid	O
in	O
convergence	O
.	O
</s>
<s>
If	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
or	O
aperture	B-General_Concept
grille	I-General_Concept
becomes	O
magnetized	O
,	O
its	O
magnetic	O
field	O
alters	O
the	O
paths	O
of	O
the	O
electron	O
beams	O
.	O
</s>
<s>
Therefore	O
,	O
it	O
is	O
important	O
that	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
or	O
aperture	B-General_Concept
grille	I-General_Concept
not	O
be	O
magnetized	O
.	O
</s>
<s>
The	O
magnetic	O
shield	O
and	O
shadow	B-General_Concept
mask	I-General_Concept
may	O
be	O
permanently	O
magnetized	O
by	O
the	O
earth	O
's	O
magnetic	O
field	O
,	O
adversely	O
affecting	O
color	O
purity	O
when	O
the	O
CRT	O
is	O
moved	O
.	O
</s>
<s>
This	O
problem	O
is	O
solved	O
with	O
a	O
built-in	O
degaussing	O
coil	O
,	O
found	O
in	O
many	O
TVs	O
and	O
computer	B-Device
monitors	I-Device
.	O
</s>
<s>
Color	O
CRT	B-Device
displays	I-Device
in	O
television	O
sets	O
and	O
computer	B-Device
monitors	I-Device
often	O
have	O
a	O
built-in	O
degaussing	O
(	O
demagnetizing	O
)	O
coil	O
mounted	O
around	O
the	O
perimeter	O
of	O
the	O
CRT	O
face	O
.	O
</s>
<s>
Upon	O
power-up	O
of	O
the	O
CRT	B-Device
display	I-Device
,	O
the	O
degaussing	O
circuit	O
produces	O
a	O
brief	O
,	O
alternating	O
current	O
through	O
the	O
coil	O
which	O
fades	O
to	O
zero	O
over	O
a	O
few	O
seconds	O
,	O
producing	O
a	O
decaying	O
alternating	O
magnetic	O
field	O
from	O
the	O
coil	O
.	O
</s>
<s>
This	O
degaussing	O
field	O
is	O
strong	O
enough	O
to	O
remove	O
shadow	B-General_Concept
mask	I-General_Concept
magnetization	O
in	O
most	O
cases	O
,	O
maintaining	O
color	O
purity	O
.	O
</s>
<s>
In	O
unusual	O
cases	O
of	O
strong	O
magnetization	O
where	O
the	O
internal	O
degaussing	O
field	O
is	O
not	O
sufficient	O
,	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
may	O
be	O
degaussed	O
externally	O
with	O
a	O
stronger	O
portable	O
degausser	O
or	O
demagnetizer	O
.	O
</s>
<s>
However	O
,	O
an	O
excessively	O
strong	O
magnetic	O
field	O
,	O
whether	O
alternating	O
or	O
constant	O
,	O
may	O
mechanically	O
deform	O
(	O
bend	O
)	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
causing	O
a	O
permanent	O
color	O
distortion	O
on	O
the	O
display	O
which	O
looks	O
very	O
similar	O
to	O
a	O
magnetization	O
effect	O
.	O
</s>
<s>
In	O
these	O
,	O
as	O
the	O
scanned	O
resolution	O
approaches	O
the	O
dot	O
pitch	O
resolution	O
,	O
moiré	O
appears	O
,	O
as	O
the	O
detail	O
being	O
displayed	O
is	O
finer	O
than	O
what	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
can	O
render	O
.	O
</s>
<s>
Aperture	B-General_Concept
grille	I-General_Concept
monitors	O
do	O
not	O
suffer	O
from	O
vertical	O
moiré	O
,	O
however	O
,	O
because	O
their	O
phosphor	O
stripes	O
have	O
no	O
vertical	O
detail	O
.	O
</s>
<s>
In	O
aperture	B-General_Concept
grille	I-General_Concept
CRTs	O
,	O
dot	O
pitch	O
is	O
replaced	O
by	O
stripe	O
pitch	O
.	O
</s>
<s>
Hitachi	O
developed	O
the	O
Enhanced	O
Dot	O
Pitch	O
(	O
EDP	O
)	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
which	O
uses	O
oval	O
holes	O
instead	O
of	O
circular	O
ones	O
,	O
with	O
respective	O
oval	O
phosphor	O
dots	O
.	O
</s>
<s>
Moiré	O
is	O
reduced	O
in	O
shadow	B-General_Concept
mask	I-General_Concept
CRTs	O
by	O
arranging	O
the	O
holes	O
in	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
in	O
a	O
honeycomb-like	O
pattern	O
.	O
</s>
<s>
Projection	O
CRTs	O
were	O
used	O
in	O
CRT	B-General_Concept
projectors	I-General_Concept
and	O
CRT	O
rear-projection	O
televisions	O
,	O
and	O
are	O
usually	O
small	O
(	O
being	O
7	O
to	O
9	O
inches	O
across	O
)	O
;	O
have	O
a	O
phosphor	O
that	O
generates	O
either	O
red	O
,	O
green	O
or	O
blue	O
light	O
,	O
thus	O
making	O
them	O
monochrome	O
CRTs	O
;	O
and	O
are	O
similar	O
in	O
construction	O
to	O
other	O
monochrome	O
CRTs	O
.	O
</s>
<s>
Beam-index	O
tubes	O
,	O
also	O
known	O
as	O
Uniray	O
,	O
Apple	O
CRT	O
or	O
Indextron	O
,	O
was	O
an	O
attempt	O
in	O
the	O
1950s	O
by	O
Philco	O
to	O
create	O
a	O
color	O
CRT	O
without	O
a	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
eliminating	O
convergence	O
and	O
purity	O
problems	O
,	O
and	O
allowing	O
for	O
shallower	O
CRTs	O
with	O
higher	O
deflection	O
angles	O
.	O
</s>
<s>
It	O
also	O
required	O
a	O
lower	O
voltage	O
power	O
supply	O
for	O
the	O
final	O
anode	O
since	O
it	O
did	O
not	O
use	O
a	O
shadow	B-General_Concept
mask	I-General_Concept
,	O
which	O
normally	O
blocks	O
around	O
80%	O
of	O
the	O
electrons	O
generated	O
by	O
the	O
electron	O
gun	O
.	O
</s>
<s>
The	O
lack	O
of	O
a	O
shadow	B-General_Concept
mask	I-General_Concept
also	O
made	O
it	O
immune	O
to	O
the	O
earth	O
's	O
magnetic	O
field	O
while	O
also	O
making	O
degaussing	O
unnecessary	O
and	O
increasing	O
image	O
brightness	O
.	O
</s>
<s>
It	O
was	O
revived	O
by	O
Sony	O
in	O
the	O
1980s	O
as	O
the	O
Indextron	O
but	O
its	O
adoption	O
was	O
limited	O
,	O
at	O
least	O
in	O
part	O
due	O
to	O
the	O
development	O
of	O
LCD	B-Device
displays	I-Device
.	O
</s>
<s>
It	O
allowed	O
for	O
single	O
CRT	O
color	O
CRT	B-General_Concept
projectors	I-General_Concept
due	O
to	O
a	O
lack	O
of	O
shadow	B-General_Concept
mask	I-General_Concept
;	O
normally	O
CRT	B-General_Concept
projectors	I-General_Concept
use	O
three	O
CRTs	O
,	O
one	O
for	O
each	O
color	O
,	O
since	O
a	O
lot	O
of	O
heat	O
is	O
generated	O
due	O
to	O
the	O
high	O
anode	O
voltage	O
and	O
beam	O
current	O
,	O
making	O
a	O
shadow	B-General_Concept
mask	I-General_Concept
impractical	O
and	O
inefficient	O
since	O
it	O
would	O
warp	O
under	O
the	O
heat	O
produced	O
(	O
shadow	B-General_Concept
masks	I-General_Concept
absorb	O
most	O
of	O
the	O
electron	O
beam	O
,	O
and	O
,	O
hence	O
,	O
most	O
of	O
the	O
energy	O
carried	O
by	O
the	O
relativistic	O
electrons	O
)	O
;	O
the	O
three	O
CRTs	O
meant	O
that	O
an	O
involved	O
calibration	O
and	O
adjustment	O
procedure	O
had	O
to	O
be	O
carried	O
out	O
during	O
installation	O
of	O
the	O
projector	O
,	O
and	O
moving	O
the	O
projector	O
would	O
require	O
it	O
to	O
be	O
recalibrated	O
.	O
</s>
<s>
A	O
single	O
CRT	O
meant	O
the	O
need	O
for	O
calibration	O
was	O
eliminated	O
,	O
but	O
brightness	O
was	O
decreased	O
since	O
the	O
CRT	B-Device
screen	I-Device
had	O
to	O
be	O
used	O
for	O
three	O
colors	O
instead	O
of	O
each	O
color	O
having	O
its	O
own	O
CRT	B-Device
screen	I-Device
.	O
</s>
<s>
A	O
stripe	O
pattern	O
also	O
imposes	O
a	O
horizontal	O
resolution	O
limit	O
;	O
in	O
contrast	O
,	O
three-screen	O
CRT	B-General_Concept
projectors	I-General_Concept
have	O
no	O
theoretical	O
resolution	O
limit	O
,	O
due	O
to	O
them	O
having	O
single	O
,	O
uniform	O
phosphor	O
coatings	O
.	O
</s>
<s>
Flat	O
CRTs	O
are	O
those	O
with	O
a	O
flat	B-General_Concept
screen	I-General_Concept
.	O
</s>
<s>
Despite	O
having	O
a	O
flat	B-General_Concept
screen	I-General_Concept
,	O
they	O
may	O
not	O
be	O
completely	O
flat	O
,	O
especially	O
on	O
the	O
inside	O
,	O
instead	O
having	O
a	O
greatly	O
increased	O
curvature	O
.	O
</s>
<s>
Such	O
completely	O
flat	O
CRTs	O
were	O
first	O
introduced	O
by	O
Zenith	O
in	O
1986	O
,	O
and	O
used	O
flat	O
tensioned	O
shadow	B-General_Concept
masks	I-General_Concept
,	O
where	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
is	O
held	O
under	O
tension	O
,	O
providing	O
increased	O
resistance	O
to	O
blooming	O
.	O
</s>
<s>
Radar	B-Algorithm
CRTs	I-Algorithm
such	O
as	O
the	O
7JP4	B-General_Concept
had	O
a	O
circular	O
screen	O
and	O
scanned	O
the	O
beam	O
from	O
the	O
center	O
outwards	O
.	O
</s>
<s>
The	O
screen	O
often	O
had	O
two	O
colors	O
,	O
often	O
a	O
bright	O
short	O
persistence	B-Device
color	O
that	O
only	O
appeared	O
as	O
the	O
beam	O
scanned	O
the	O
display	O
and	O
a	O
long	O
persistence	B-Device
phosphor	O
afterglow	O
.	O
</s>
<s>
When	O
the	O
beam	O
strikes	O
the	O
phosphor	O
,	O
the	O
phosphor	O
brightly	O
illuminates	O
,	O
and	O
when	O
the	O
beam	O
leaves	O
,	O
the	O
dimmer	O
long	O
persistence	B-Device
afterglow	O
would	O
remain	O
lit	O
where	O
the	O
beam	O
struck	O
the	O
phosphor	O
,	O
alongside	O
the	O
radar	B-Application
targets	O
that	O
were	O
"	O
written	O
"	O
by	O
the	O
beam	O
,	O
until	O
the	O
beam	O
re-struck	O
the	O
phosphor	O
.	O
</s>
<s>
The	O
use	O
of	O
a	O
long	O
persistence	B-Device
phosphor	O
may	O
allow	O
the	O
image	O
to	O
be	O
observed	O
after	O
the	O
event	O
,	O
but	O
only	O
for	O
a	O
few	O
seconds	O
at	O
best	O
.	O
</s>
<s>
This	O
limitation	O
can	O
be	O
overcome	O
by	O
the	O
use	O
of	O
a	O
direct	O
view	O
storage	O
cathode-ray	B-Device
tube	I-Device
(	O
storage	O
tube	O
)	O
.	O
</s>
<s>
By	O
varying	O
this	O
voltage	O
a	O
variable	O
persistence	B-Device
is	O
obtained	O
.	O
</s>
<s>
Vector	O
monitors	O
were	O
used	O
in	O
early	O
computer	O
aided	O
design	O
systems	O
and	O
are	O
in	O
some	O
late-1970s	O
to	O
mid-1980s	O
arcade	O
games	O
such	O
as	O
Asteroids	B-Application
.	O
</s>
<s>
They	O
draw	O
graphics	O
point-to-point	O
,	O
rather	O
than	O
scanning	O
a	O
raster	B-Algorithm
.	O
</s>
<s>
The	O
Williams	B-General_Concept
tube	I-General_Concept
or	O
Williams-Kilburn	B-General_Concept
tube	I-General_Concept
was	O
a	O
cathode-ray	B-Device
tube	I-Device
used	O
to	O
electronically	O
store	O
binary	O
data	O
.	O
</s>
<s>
In	O
contrast	O
to	O
other	O
CRTs	O
in	O
this	O
article	O
,	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
was	O
not	O
a	O
display	O
device	O
,	O
and	O
in	O
fact	O
could	O
not	O
be	O
viewed	O
since	O
a	O
metal	O
plate	O
covered	O
its	O
screen	O
.	O
</s>
<s>
In	O
some	O
vacuum	B-General_Concept
tube	O
radio	O
sets	O
,	O
a	O
"	B-General_Concept
Magic	I-General_Concept
Eye	I-General_Concept
"	I-General_Concept
or	I-General_Concept
"	I-General_Concept
Tuning	I-General_Concept
Eye	I-General_Concept
"	I-General_Concept
tube	I-General_Concept
was	O
provided	O
to	O
assist	O
in	O
tuning	O
the	O
receiver	O
.	O
</s>
<s>
These	O
incorporate	O
a	O
perforated	O
metal	O
character	O
mask	O
(	O
stencil	B-Algorithm
)	O
,	O
which	O
shapes	O
a	O
wide	O
electron	O
beam	O
to	O
form	O
a	O
character	O
on	O
the	O
screen	O
.	O
</s>
<s>
Having	O
little	O
of	O
the	O
complexities	O
of	O
a	O
standard	O
CRT	O
,	O
the	O
tube	O
required	O
a	O
relatively	O
simple	O
driving	O
circuit	O
,	O
and	O
as	O
the	O
image	O
was	O
projected	O
on	O
the	O
glass	O
face	O
,	O
it	O
provided	O
a	O
much	O
wider	O
viewing	O
angle	O
than	O
competitive	O
types	O
(	O
e.g.	O
,	O
nixie	B-Application
tubes	I-Application
)	O
.	O
</s>
<s>
Flood-beam	O
CRTs	O
are	O
small	O
tubes	O
that	O
are	O
arranged	O
as	O
pixels	O
for	O
large	O
video	B-Device
walls	I-Device
like	O
Jumbotrons	B-Application
.	O
</s>
<s>
The	O
first	O
screen	O
using	O
this	O
technology	O
(	O
called	O
Diamond	B-General_Concept
Vision	I-General_Concept
by	O
Mitsubishi	O
Electric	O
)	O
was	O
introduced	O
by	O
Mitsubishi	O
Electric	O
for	O
the	O
1980	O
Major	O
League	O
Baseball	O
All-Star	O
Game	O
.	O
</s>
<s>
In	O
the	O
late	O
1990s	O
and	O
early	O
2000s	O
Philips	O
Research	O
Laboratories	O
experimented	O
with	O
a	O
type	O
of	O
thin	O
CRT	O
known	O
as	O
the	O
Zeus	O
display	O
,	O
which	O
contained	O
CRT-like	O
functionality	O
in	O
a	O
flat-panel	B-General_Concept
display	I-General_Concept
.	O
</s>
<s>
CRTs	O
can	O
emit	O
a	O
small	O
amount	O
of	O
X-ray	B-Library
radiation	O
;	O
this	O
is	O
a	O
result	O
of	O
the	O
electron	O
beam	O
's	O
bombardment	O
of	O
the	O
shadow	O
mask/aperture	O
grille	O
and	O
phosphors	O
,	O
which	O
produces	O
bremsstrahlung	O
(	O
braking	O
radiation	O
)	O
as	O
the	O
high-energy	O
electrons	O
are	O
decelerated	O
.	O
</s>
<s>
The	O
density	O
of	O
the	O
x-rays	B-Library
that	O
would	O
be	O
generated	O
by	O
a	O
CRT	O
is	O
low	O
because	O
the	O
raster	B-Algorithm
scan	O
of	O
a	O
typical	O
CRT	O
distributes	O
the	O
energy	O
of	O
the	O
electron	O
beam	O
across	O
the	O
entire	O
screen	O
.	O
</s>
<s>
Voltages	O
above	O
15,000	O
volts	O
are	O
enough	O
to	O
generate	O
"	O
soft	O
"	O
x-rays	B-Library
.	O
</s>
<s>
However	O
,	O
since	O
CRTs	O
may	O
stay	O
on	O
for	O
several	O
hours	O
at	O
a	O
time	O
,	O
the	O
amount	O
of	O
x-rays	B-Library
generated	O
by	O
the	O
CRT	O
may	O
become	O
significant	O
,	O
hence	O
the	O
importance	O
of	O
using	O
materials	O
to	O
shield	O
against	O
x-rays	B-Library
,	O
such	O
as	O
the	O
thick	O
leaded	O
glass	O
and	O
barium-strontium	O
glass	O
used	O
in	O
CRTs	O
.	O
</s>
<s>
Concerns	O
about	O
x-rays	B-Library
emitted	O
by	O
CRTs	O
began	O
in	O
1967	O
when	O
it	O
was	O
found	O
that	O
TV	O
sets	O
made	O
by	O
General	O
Electric	O
were	O
emitting	O
"	O
X-radiation	O
in	O
excess	O
of	O
desirable	O
levels	O
"	O
.	O
</s>
<s>
Flicker	O
is	O
commonly	O
associated	O
with	O
CRT	O
as	O
most	O
televisions	O
run	O
at	O
50Hz	O
(	O
PAL	B-Language
)	O
or	O
60Hz	O
(	O
NTSC	O
)	O
,	O
although	O
there	O
are	O
some	O
100Hz	O
PAL	B-Language
televisions	O
that	O
are	O
flicker-free	B-General_Concept
.	O
</s>
<s>
Typically	O
only	O
low-end	O
monitors	O
run	O
at	O
such	O
low	O
frequencies	O
,	O
with	O
most	O
computer	B-Device
monitors	I-Device
supporting	O
at	O
least	O
75Hz	O
and	O
high-end	O
monitors	O
capable	O
of	O
100Hz	O
or	O
more	O
to	O
eliminate	O
any	O
perception	O
of	O
flicker	O
.	O
</s>
<s>
Though	O
the	O
100Hz	O
PAL	B-Language
was	O
often	O
achieved	O
using	O
interleaved	O
scanning	O
,	O
dividing	O
the	O
circuit	O
and	O
scan	O
into	O
two	O
beams	O
of	O
50Hz	O
.	O
</s>
<s>
Non-computer	O
CRTs	O
or	O
CRT	O
for	O
sonar	B-Application
or	O
radar	B-Application
may	O
have	O
long	O
persistence	B-Device
phosphor	O
and	O
are	O
thus	O
flicker	B-General_Concept
free	I-General_Concept
.	O
</s>
<s>
If	O
the	O
persistence	B-Device
is	O
too	O
long	O
on	O
a	O
video	O
display	O
,	O
moving	O
images	O
will	O
be	O
blurred	O
.	O
</s>
<s>
50Hz/60Hz	O
CRTs	O
used	O
for	O
television	O
operate	O
with	O
horizontal	O
scanning	O
frequencies	O
of	O
15,750	O
and	O
15,734	O
.25Hz	O
(	O
for	O
NTSC	O
systems	O
)	O
or	O
15,625	O
Hz	O
(	O
for	O
PAL	B-Language
systems	O
)	O
.	O
</s>
<s>
This	O
problem	O
does	O
not	O
occur	O
on	O
100/120Hz	O
TVs	O
and	O
on	O
non-CGA	O
(	O
Color	O
Graphics	O
Adapter	O
)	O
computer	B-Device
displays	I-Device
,	O
because	O
they	O
use	O
much	O
higher	O
horizontal	O
scanning	O
frequencies	O
that	O
produce	O
sound	O
which	O
is	O
inaudible	O
to	O
humans	O
(	O
22kHz	O
to	O
over	O
100kHz	O
)	O
.	O
</s>
<s>
High	O
vacuum	B-General_Concept
inside	O
glass-walled	O
cathode-ray	B-Device
tubes	I-Device
permits	O
electron	O
beams	O
to	O
fly	O
freely	O
—	O
without	O
colliding	O
into	O
molecules	O
of	O
air	O
or	O
other	O
gas	O
.	O
</s>
<s>
If	O
the	O
glass	O
is	O
damaged	O
,	O
atmospheric	O
pressure	O
can	O
collapse	O
the	O
vacuum	B-General_Concept
tube	O
into	O
dangerous	O
fragments	O
which	O
accelerate	O
inward	O
and	O
then	O
spray	O
at	O
high	O
speed	O
in	O
all	O
directions	O
.	O
</s>
<s>
Although	O
modern	O
cathode-ray	B-Device
tubes	I-Device
used	O
in	O
televisions	O
and	O
computer	B-Device
displays	I-Device
have	O
epoxy-bonded	O
face-plates	O
or	O
other	O
measures	O
to	O
prevent	O
shattering	O
of	O
the	O
envelope	O
,	O
CRTs	O
must	O
be	O
handled	O
carefully	O
to	O
avoid	O
personal	O
injury	O
.	O
</s>
<s>
This	O
makes	O
the	O
band	O
an	O
integral	O
component	O
that	O
should	O
never	O
be	O
removed	O
from	O
an	O
intact	O
CRT	O
that	O
still	O
has	O
a	O
vacuum	B-General_Concept
;	O
attempting	O
to	O
remove	O
it	O
may	O
cause	O
the	O
CRT	O
to	O
implode	O
.	O
</s>
<s>
Special	O
TEMPEST	B-Application
shielding	O
can	O
mitigate	O
this	O
effect	O
.	O
</s>
<s>
Due	O
to	O
the	O
toxins	O
contained	O
in	O
CRT	B-Device
monitors	I-Device
the	O
United	O
States	O
Environmental	O
Protection	O
Agency	O
created	O
rules	O
(	O
in	O
October	O
2001	O
)	O
stating	O
that	O
CRTs	O
must	O
be	O
brought	O
to	O
special	O
e-waste	O
recycling	O
facilities	O
.	O
</s>
<s>
In	O
November	O
2002	O
,	O
the	O
EPA	O
began	O
fining	O
companies	O
that	O
disposed	O
of	O
CRTs	O
through	O
landfills	B-Application
or	O
incineration	O
.	O
</s>
<s>
The	O
United	O
States	O
Environmental	O
Protection	O
Agency	O
(	O
EPA	O
)	O
includes	O
discarded	O
CRT	B-Device
monitors	I-Device
in	O
its	O
category	O
of	O
"	O
hazardous	O
household	O
waste	O
"	O
but	O
considers	O
CRTs	O
that	O
have	O
been	O
set	O
aside	O
for	O
testing	O
to	O
be	O
commodities	O
if	O
they	O
are	O
not	O
discarded	O
,	O
speculatively	O
accumulated	O
,	O
or	O
left	O
unprotected	O
from	O
weather	O
and	O
other	O
damage	O
.	O
</s>
