<s>
Mechanical	B-Architecture
television	I-Architecture
or	O
mechanical	B-Architecture
scan	I-Architecture
television	I-Architecture
is	O
an	O
obsolete	O
television	O
system	O
that	O
relies	O
on	O
a	O
mechanical	O
scanning	O
device	O
,	O
such	O
as	O
a	O
rotating	O
disk	O
with	O
holes	O
in	O
it	O
or	O
a	O
rotating	O
mirror	O
drum	O
,	O
to	O
scan	O
the	O
scene	O
and	O
generate	O
the	O
video	O
signal	O
,	O
and	O
a	O
similar	O
mechanical	O
device	O
at	O
the	O
receiver	O
to	O
display	O
the	O
picture	O
.	O
</s>
<s>
This	O
contrasts	O
with	O
vacuum	O
tube	O
electronic	O
television	O
technology	O
,	O
using	O
electron	O
beam	O
scanning	O
methods	O
,	O
for	O
example	O
in	O
cathode	B-Device
ray	I-Device
tube	I-Device
(	O
CRT	B-Device
)	O
televisions	O
.	O
</s>
<s>
Subsequently	O
,	O
modern	O
solid-state	O
liquid-crystal	B-Device
displays	I-Device
(	O
LCD	B-Device
)	O
are	O
now	O
used	O
to	O
create	O
and	O
display	O
television	O
pictures	O
.	O
</s>
<s>
In	O
the	O
U.S.	O
,	O
experimental	O
stations	O
such	O
as	O
W2XAB	O
in	O
New	O
York	O
City	O
began	O
broadcasting	O
mechanical	B-Architecture
television	I-Architecture
programs	O
in	O
1931	O
but	O
discontinued	O
operations	O
on	O
February	O
20	O
,	O
1933	O
,	O
until	O
returning	O
with	O
an	O
all-electronic	O
system	O
in	O
1939	O
.	O
</s>
<s>
A	O
mechanical	B-Architecture
television	I-Architecture
receiver	O
was	O
also	O
called	O
a	O
televisor	B-Architecture
.	O
</s>
<s>
Willoughby	O
Smith	O
discovered	O
the	O
photoconductivity	O
of	O
the	O
element	O
selenium	B-Library
in	O
1873	O
,	O
laying	O
the	O
groundwork	O
for	O
the	O
selenium	B-Library
cell	O
which	O
was	O
used	O
as	O
a	O
pickup	O
in	O
most	O
mechanical	O
scan	O
systems	O
.	O
</s>
<s>
In	O
1885	O
,	O
Henry	O
Sutton	O
in	O
Ballarat	O
,	O
Australia	O
designed	O
what	O
he	O
called	O
a	O
telephane	O
for	O
transmission	O
of	O
images	O
via	O
telegraph	O
wires	O
,	O
based	O
on	O
the	O
Nipkow	O
spinning	O
disk	O
system	O
,	O
selenium	B-Library
photocell	O
,	O
Nicol	O
prisms	O
and	O
Kerr	O
effect	O
cell	O
.	O
</s>
<s>
The	O
first	O
demonstration	O
of	O
the	O
instantaneous	O
transmission	O
of	O
images	O
was	O
made	O
by	O
a	O
German	O
physicist	O
,	O
Ernst	O
Ruhmer	O
,	O
who	O
arranged	O
25	O
selenium	B-Library
cells	O
as	O
the	O
picture	B-Algorithm
elements	I-Algorithm
for	O
a	O
television	O
receiver	O
.	O
</s>
<s>
The	O
limited	O
number	O
of	O
elements	O
meant	O
his	O
device	O
was	O
only	O
capable	O
of	O
representing	O
simple	O
geometric	O
shapes	O
,	O
and	O
the	O
cost	O
was	O
very	O
high	O
;	O
at	O
a	O
price	O
of	O
£15	O
(	O
US$45	O
)	O
per	O
selenium	B-Library
cell	O
,	O
he	O
estimated	O
that	O
a	O
4,000	O
cell	O
system	O
would	O
cost	O
£	O
60,000	O
(	O
US$	O
180,000	O
)	O
,	O
and	O
a	O
10,000	O
cell	O
mechanism	O
capable	O
of	O
reproducing	O
"	O
a	O
scene	O
or	O
event	O
requiring	O
the	O
background	O
of	O
a	O
landscape	O
"	O
would	O
cost	O
£	O
150,000	O
(	O
US$	O
450,000	O
)	O
.	O
</s>
<s>
A	O
matrix	O
of	O
64	O
selenium	B-Library
cells	O
,	O
individually	O
wired	O
to	O
a	O
mechanical	O
commutator	O
,	O
served	O
as	O
an	O
electronic	O
retina	O
.	O
</s>
<s>
The	O
8x8	O
pixel	B-Algorithm
resolution	O
in	O
this	O
proof-of-concept	O
demonstration	O
was	O
just	O
sufficient	O
to	O
clearly	O
transmit	O
individual	O
letters	O
of	O
the	O
alphabet	O
.	O
</s>
<s>
In	O
1911	O
,	O
Boris	O
Rosing	O
and	O
his	O
student	O
Vladimir	O
Zworykin	O
created	O
a	O
system	O
that	O
used	O
a	O
mechanical	O
mirror-drum	O
scanner	O
to	O
transmit	O
,	O
in	O
Zworykin	O
's	O
words	O
,	O
"	O
very	O
crude	O
images	O
"	O
over	O
wires	O
to	O
the	O
"	O
Braun	B-Device
tube	I-Device
"	O
(	O
cathode	B-Device
ray	I-Device
tube	I-Device
or	O
"	O
CRT	B-Device
"	O
)	O
in	O
the	O
receiver	O
.	O
</s>
<s>
Moving	O
images	O
were	O
not	O
possible	O
because	O
,	O
in	O
the	O
scanner	O
,	O
"	O
the	O
sensitivity	O
was	O
not	O
enough	O
and	O
the	O
selenium	B-Library
cell	O
was	O
very	O
laggy	O
"	O
.	O
</s>
<s>
As	O
each	O
hole	O
in	O
the	O
disk	O
passed	O
by	O
,	O
one	O
scan	B-Algorithm
line	I-Algorithm
of	O
the	O
image	O
was	O
reproduced	O
.	O
</s>
<s>
Baird	O
's	O
disk	O
had	O
30	O
holes	O
,	O
producing	O
an	O
image	O
with	O
only	O
30	O
scan	B-Algorithm
lines	I-Algorithm
,	O
just	O
enough	O
to	O
recognize	O
a	O
human	O
face	O
.	O
</s>
<s>
In	O
1929	O
,	O
he	O
became	O
involved	O
in	O
the	O
first	O
experimental	O
mechanical	B-Architecture
television	I-Architecture
service	O
in	O
Germany	O
.	O
</s>
<s>
In	O
1932	O
,	O
he	O
demonstrated	O
ultra-short	B-Algorithm
wave	I-Algorithm
television	O
.	O
</s>
<s>
On	O
December	O
25	O
,	O
1925	O
,	O
Kenjiro	O
Takayanagi	O
demonstrated	O
a	O
television	O
system	O
with	O
a	O
40-line	O
resolution	O
that	O
employed	O
a	O
Nipkow	O
disk	O
scanner	O
and	O
CRT	B-Device
display	I-Device
at	O
Hamamatsu	O
Industrial	O
High	O
School	O
in	O
Japan	O
.	O
</s>
<s>
Herbert	O
E	O
.	O
Ives	O
and	O
Frank	O
Gray	O
of	O
Bell	O
Telephone	O
Laboratories	O
gave	O
a	O
dramatic	O
demonstration	O
of	O
mechanical	B-Architecture
television	I-Architecture
on	O
April	O
7	O
,	O
1927	O
.	O
</s>
<s>
A	O
flying-spot	B-Algorithm
scanner	I-Algorithm
beam	O
illuminated	O
these	O
subjects	O
.	O
</s>
<s>
Television	O
historian	O
Albert	O
Abramson	O
underscored	O
the	O
significance	O
of	O
the	O
Bell	O
Labs	O
demonstration	O
:	O
"	O
It	O
was	O
in	O
fact	O
the	O
best	O
demonstration	O
of	O
a	O
mechanical	B-Architecture
television	I-Architecture
system	O
ever	O
made	O
to	O
this	O
time	O
.	O
</s>
<s>
Because	O
only	O
a	O
limited	O
number	O
of	O
holes	O
could	O
be	O
made	O
in	O
the	O
disks	O
,	O
and	O
disks	O
beyond	O
a	O
certain	O
diameter	O
became	O
impractical	O
,	O
image	O
resolution	O
on	O
mechanical	B-Architecture
television	I-Architecture
broadcasts	O
was	O
relatively	O
low	O
,	O
ranging	O
from	O
about	O
30	O
lines	O
up	O
to	O
120	O
or	O
so	O
.	O
</s>
<s>
Nevertheless	O
,	O
the	O
image	O
quality	O
of	O
30-line	O
transmissions	O
steadily	O
improved	O
with	O
technical	O
advances	O
,	O
and	O
by	O
1933	O
the	O
UK	O
broadcasts	O
using	O
the	O
Baird	B-Architecture
system	I-Architecture
were	O
remarkably	O
clear.Donald	O
F	O
.	O
McLean	O
,	O
Restoring	O
Baird	O
's	O
Image	O
(	O
London	O
:	O
IEEE	O
,	O
2000	O
)	O
,	O
p	O
.	O
184	O
.	O
</s>
<s>
right|thumb|A	O
color	O
televisor	B-Architecture
.	O
</s>
<s>
At	O
the	O
receiver	O
,	O
a	O
synchronized	O
disc	O
paints	O
the	O
same	O
hues	O
over	O
the	O
CRT	B-Device
.	O
</s>
<s>
The	O
most	O
prominent	O
of	O
these	O
adapters	O
is	O
Col-R-Tel	O
,	O
a	O
1955	O
NTSC	O
to	O
field-sequential	O
converter.Hawes	O
Mechanical	B-Architecture
Television	I-Architecture
Archive	O
,	O
How	O
Col-R-Tel	O
Works	O
.	O
</s>
<s>
The	O
advancement	O
of	O
vacuum	O
tube	O
electronic	O
television	O
(	O
including	O
image	O
dissectors	O
and	O
other	O
camera	O
tubes	O
and	O
cathode	B-Device
ray	I-Device
tubes	I-Device
for	O
the	O
reproducer	O
)	O
marked	O
the	O
beginning	O
of	O
the	O
end	O
for	O
mechanical	O
systems	O
as	O
the	O
dominant	O
form	O
of	O
television	O
.	O
</s>
<s>
Mechanical	B-Architecture
TV	I-Architecture
usually	O
only	O
produced	O
small	O
images	O
.	O
</s>
<s>
Vacuum	O
tube	O
television	O
,	O
first	O
demonstrated	O
in	O
September	O
1927	O
in	O
San	O
Francisco	O
by	O
Philo	O
Farnsworth	O
,	O
and	O
then	O
publicly	O
by	O
Farnsworth	O
at	O
the	O
Franklin	O
Institute	O
in	O
Philadelphia	O
in	O
1934	O
,	O
was	O
rapidly	O
overtaking	O
mechanical	B-Architecture
television	I-Architecture
.	O
</s>
<s>
The	O
last	O
mechanical	B-Architecture
television	I-Architecture
broadcasts	O
ended	O
in	O
1939	O
at	O
stations	O
run	O
by	O
a	O
handful	O
of	O
public	O
universities	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
Also	O
associated	O
with	O
this	O
is	O
slow-scan	O
TV	O
–	O
although	O
that	O
typically	O
used	O
electronic	O
systems	O
utilising	O
the	O
P7	O
CRT	B-Device
until	O
the	O
1980s	O
and	O
PCs	B-Device
thereafter	O
.	O
</s>
<s>
There	O
are	O
three	O
known	O
mechanical	O
monitor	O
forms	O
:	O
two	O
fax	O
printer-like	O
monitors	O
made	O
in	O
the	O
1970s	O
,	O
and	O
in	O
2013	O
a	O
small	O
drum	O
monitor	O
with	O
a	O
coating	O
of	O
glow	O
paint	O
where	O
the	O
image	O
is	O
painted	O
on	O
the	O
rotating	O
drum	O
with	O
a	O
UV	B-Application
laser	O
.	O
</s>
<s>
Digital	B-General_Concept
Light	I-General_Concept
Processing	I-General_Concept
(	O
DLP	O
)	O
projectors	O
use	O
an	O
array	O
of	O
tiny	O
(	O
16	O
μm2	O
)	O
electrostatically-actuated	O
mirrors	O
selectively	O
reflecting	O
a	O
light	O
source	O
to	O
create	O
an	O
image	O
.	O
</s>
<s>
Many	O
low-end	O
DLP	O
systems	O
also	O
use	O
a	O
color	O
wheel	O
to	O
provide	O
a	O
sequential	O
color	O
image	O
,	O
a	O
feature	O
that	O
was	O
common	O
on	O
many	O
early	O
color	O
television	O
systems	O
before	O
the	O
shadow	B-General_Concept
mask	I-General_Concept
CRT	B-Device
provided	O
a	O
practical	O
method	O
for	O
producing	O
a	O
simultaneous	O
color	O
image	O
.	O
</s>
<s>
Laser	O
lighting	O
display	O
techniques	O
are	O
combined	O
with	O
computer	O
emulation	B-Application
in	O
the	O
LaserMAME	O
project	O
.	O
</s>
<s>
Laser	O
light	O
reflected	O
from	O
computer-controlled	O
mirrors	O
traces	O
out	O
images	O
generated	O
by	O
classic	O
arcade	O
software	O
which	O
is	O
executed	O
by	O
a	O
specially	O
modified	O
version	O
of	O
the	O
MAME	B-Device
emulation	B-Application
software	I-Application
.	O
</s>
<s>
The	O
most	O
common	O
method	O
for	O
creating	O
the	O
video	O
signal	O
was	O
the	O
"	O
flying	B-Algorithm
spot	I-Algorithm
scanner	I-Algorithm
"	O
,	O
developed	O
as	O
a	O
remedy	O
for	O
the	O
low	O
sensitivity	O
that	O
photoelectric	O
cells	O
had	O
at	O
the	O
time	O
.	O
</s>
<s>
Instead	O
of	O
a	O
television	O
camera	O
that	O
took	O
pictures	O
,	O
a	O
flying	B-Algorithm
spot	I-Algorithm
scanner	I-Algorithm
projected	O
a	O
bright	O
spot	O
of	O
light	O
that	O
scanned	O
rapidly	O
across	O
the	O
subject	O
scene	O
in	O
a	O
raster	O
pattern	O
,	O
in	O
a	O
darkened	O
studio	O
.	O
</s>
<s>
Each	O
sweep	O
of	O
the	O
spot	O
across	O
the	O
scene	O
produced	O
a	O
"	O
scan	B-Algorithm
line	I-Algorithm
"	O
of	O
the	O
picture	O
.	O
</s>
<s>
A	O
single	O
"	O
frame	O
"	O
of	O
the	O
picture	O
was	O
typically	O
made	O
up	O
of	O
24	O
,	O
48	O
,	O
or	O
60	O
scan	B-Algorithm
lines	I-Algorithm
.	O
</s>
<s>
Like	O
mechanical	B-Architecture
television	I-Architecture
itself	O
,	O
flying	O
spot	O
technology	O
grew	O
out	O
of	O
phototelegraphy	O
(	O
facsimile	O
)	O
.	O
</s>
<s>
This	O
year	O
was	O
by	O
far	O
not	O
the	O
end	O
of	O
flying	B-Algorithm
spot	I-Algorithm
scanner	I-Algorithm
technology	O
.	O
</s>
<s>
The	O
German	O
inventor	O
Manfred	O
von	O
Ardenne	O
designed	O
a	O
flying	B-Algorithm
spot	I-Algorithm
scanner	I-Algorithm
with	O
a	O
CRT	B-Device
as	O
the	O
light	O
source	O
.	O
</s>
<s>
In	O
1928	O
,	O
Ray	O
Kell	O
from	O
the	O
United	O
States	O
 '	O
General	O
Electric	O
proved	O
that	O
flying	B-Algorithm
spot	I-Algorithm
scanners	I-Algorithm
could	O
work	O
outdoors	O
.	O
</s>
<s>
thumb|A	O
scene	O
being	O
televised	O
by	O
flying	B-Algorithm
spot	I-Algorithm
scanner	I-Algorithm
in	O
a	O
television	O
studio	O
in	O
1931	O
.	O
</s>
<s>
The	O
Nipkow	O
disk	O
in	O
the	O
flying	B-Algorithm
spot	I-Algorithm
scanner	I-Algorithm
(	O
bottom	O
)	O
projects	O
a	O
spot	O
of	O
light	O
that	O
scans	O
the	O
subject	O
in	O
a	O
raster	O
pattern	O
in	O
the	O
darkened	O
studio	O
.	O
</s>
<s>
A	O
few	O
mechanical	B-Architecture
TV	I-Architecture
systems	O
could	O
produce	O
images	O
several	O
feet	O
or	O
meters	O
wide	O
and	O
of	O
comparable	O
quality	O
to	O
the	O
cathode	B-Device
ray	I-Device
tube	I-Device
(	O
CRT	B-Device
)	O
televisions	O
that	O
were	O
to	O
follow	O
.	O
</s>
<s>
CRT	B-Device
technology	O
at	O
that	O
time	O
was	O
limited	O
to	O
small	O
,	O
low-brightness	O
screens	O
.	O
</s>
<s>
Perhaps	O
the	O
best	O
mechanical	B-Architecture
televisions	I-Architecture
of	O
the	O
1930s	O
used	O
the	O
Scophony	O
system	O
,	O
which	O
could	O
produce	O
images	O
of	O
more	O
than	O
400	O
lines	O
and	O
display	O
them	O
on	O
screens	O
at	O
least	O
in	O
size	O
(	O
at	O
least	O
a	O
few	O
models	O
of	O
this	O
type	O
were	O
actually	O
produced	O
)	O
.	O
</s>
<s>
The	O
position	O
of	O
a	O
framing	O
mask	O
before	O
the	O
Nipkow	O
disk	O
determines	O
the	O
scan	B-Algorithm
line	I-Algorithm
orientation	O
.	O
</s>
<s>
Placement	O
of	O
the	O
framing	O
mask	O
at	O
the	O
left	O
or	O
right	O
side	O
of	O
the	O
disk	O
gives	O
vertical	O
scan	B-Algorithm
lines	I-Algorithm
.	O
</s>
<s>
Placement	O
at	O
the	O
top	O
or	O
bottom	O
of	O
the	O
disk	O
gives	O
horizontal	O
scan	B-Algorithm
lines	I-Algorithm
.	O
</s>
<s>
In	O
the	O
days	O
of	O
commercial	O
mechanical	B-Architecture
television	I-Architecture
transmissions	O
,	O
a	O
system	O
of	O
recording	O
images	O
(	O
but	O
not	O
sound	O
)	O
was	O
developed	O
,	O
using	O
a	O
modified	O
gramophone	O
recorder	O
.	O
</s>
<s>
Scottish	O
computer	O
engineer	O
Donald	O
F	O
.	O
McLean	O
has	O
painstakingly	O
reconstructed	O
the	O
analogue	O
playback	O
technology	O
required	O
to	O
view	O
these	O
recordings	O
,	O
and	O
has	O
given	O
lectures	O
and	O
presentations	O
on	O
his	O
collection	O
of	O
mechanical	B-Architecture
television	I-Architecture
recordings	O
made	O
between	O
1925	O
and	O
1933.The	O
World	O
's	O
Earliest	O
Television	O
Recordings	O
.	O
</s>
