<s>
An	O
ATSC	B-Device
(	O
Advanced	O
Television	O
Systems	O
Committee	O
)	O
tuner	B-Device
,	O
often	O
called	O
an	O
ATSC	B-Device
receiver	I-Device
or	O
HDTV	B-Device
tuner	I-Device
,	O
is	O
a	O
type	O
of	O
television	B-Device
tuner	I-Device
that	O
allows	O
reception	O
of	O
digital	B-Application
television	I-Application
(	O
DTV	O
)	O
television	O
channels	O
that	O
use	O
ATSC	B-Device
standards	I-Device
,	O
as	O
transmitted	O
by	O
television	O
stations	O
in	O
North	O
America	O
,	O
parts	O
of	O
Central	O
America	O
,	O
and	O
South	O
Korea	O
.	O
</s>
<s>
Such	O
tuners	B-Device
are	O
usually	O
integrated	O
into	O
a	O
television	O
set	O
,	O
VCR	O
,	O
digital	B-Application
video	I-Application
recorder	I-Application
(	O
DVR	O
)	O
,	O
or	O
set-top	O
box	O
which	O
provides	O
audio/video	O
output	O
connectors	O
of	O
various	O
types	O
.	O
</s>
<s>
Another	O
type	O
of	O
television	B-Device
tuner	I-Device
is	O
a	O
digital	B-Application
television	I-Application
adapter	O
(	O
DTA	O
)	O
with	O
an	O
analog	O
passthrough	O
.	O
</s>
<s>
The	O
terms	O
"	O
tuner	B-Device
"	O
and	O
"	O
receiver	B-Device
"	O
are	O
used	O
loosely	O
,	O
and	O
it	O
is	O
perhaps	O
more	O
appropriately	O
called	O
an	O
ATSC	B-Device
receiver	I-Device
,	O
with	O
the	O
tuner	B-Device
being	O
part	O
of	O
the	O
receiver	B-Device
(	O
see	O
Metonymy	O
)	O
.	O
</s>
<s>
The	O
receiver	B-Device
generates	O
the	O
audio	O
and	O
video	O
(	O
AV	O
)	O
signals	O
needed	O
for	O
television	O
,	O
and	O
performs	O
the	O
following	O
tasks	O
:	O
demodulation	B-Device
;	O
error	B-Error_Name
correction	I-Error_Name
;	O
MPEG	O
transport	O
stream	O
demultiplexing	B-Architecture
;	O
decompression	O
;	O
AV	B-Protocol
synchronization	I-Protocol
;	O
and	O
media	O
reformatting	O
to	O
match	O
what	O
is	O
optimal	O
input	O
for	O
one	O
's	O
TV	O
.	O
</s>
<s>
Examples	O
of	O
media	O
reformatting	O
include	O
:	O
interlace	O
to	O
progressive	B-Device
scan	I-Device
or	O
vice	O
versa	O
;	O
picture	O
resolutions	O
;	O
aspect	B-General_Concept
ratio	I-General_Concept
conversions	O
(	O
16:9	O
to	O
or	O
from	O
4:3	O
)	O
;	O
frame	O
rate	O
conversion	O
;	O
and	O
image	B-Algorithm
scaling	I-Algorithm
.	O
</s>
<s>
Some	O
ATSC	B-Device
receivers	I-Device
,	O
mostly	O
those	O
in	O
HDTV	B-Device
TV	O
sets	O
,	O
will	O
stretch	O
automatically	O
,	O
either	O
by	O
detecting	O
black	O
bars	O
or	O
by	O
reading	O
the	O
Active	O
Format	O
Descriptor	O
(	O
AFD	O
)	O
.	O
</s>
<s>
An	O
ATSC	B-Device
tuner	I-Device
works	O
by	O
generating	O
audio	O
and	O
video	O
signals	O
that	O
are	O
picked	O
up	O
from	O
over-the-air	O
broadcast	O
television	O
.	O
</s>
<s>
ATSC	B-Device
tuners	I-Device
provide	O
the	O
following	O
functions	O
:	O
selective	O
tuning	O
;	O
demodulation	B-Device
;	O
transport	O
stream	O
demultiplexing	B-Architecture
;	O
decompression	O
;	O
error	B-Error_Name
correction	I-Error_Name
;	O
analog-to-digital	O
conversion	O
;	O
AV	B-Protocol
synchronization	I-Protocol
;	O
and	O
media	O
reformatting	O
to	O
fit	O
the	O
specific	O
type	O
of	O
TV	O
screen	O
optimally	O
.	O
</s>
<s>
Selective	O
tuning	O
is	O
the	O
process	O
by	O
which	O
the	O
radio	O
frequency	O
(	O
RF	O
)	O
of	O
the	O
television	O
channel	O
is	O
selected	O
by	O
a	O
receiver	B-Device
from	O
within	O
a	O
band	O
of	O
transmitted	O
RF	O
signals	O
.	O
</s>
<s>
The	O
tuner	B-Device
usually	O
performs	O
the	O
function	O
of	O
frequency-agile	O
selection	O
,	O
along	O
with	O
rejection	O
of	O
unwanted	O
out-of-band	O
signals	O
.	O
</s>
<s>
"	O
Demodulation	B-Device
"	O
means	O
transforming	O
the	O
signal	O
from	O
the	O
tuner	B-Device
into	O
a	O
signal	O
that	O
a	O
TV	O
set	O
can	O
use	O
to	O
produce	O
images	O
and	O
sound	O
without	O
further	O
consideration	O
for	O
the	O
frequency	O
at	O
which	O
it	O
was	O
transmitted	O
.	O
</s>
<s>
It	O
is	O
separation	O
of	O
a	O
standard	O
baseband	B-Algorithm
signal	I-Algorithm
from	O
the	O
RF	O
carrier	O
that	O
was	O
used	O
to	O
transmit	O
it	O
through	O
the	O
air	O
(	O
or	O
down	O
a	O
coaxial	O
cable	O
or	O
other	O
long-distance	O
medium	O
.	O
)	O
</s>
<s>
ATSC	B-Device
as	O
implemented	O
in	O
the	O
US	O
uses	O
8VSB	B-Device
modulation	O
,	O
which	O
requires	O
less	O
power	O
to	O
transmit	O
,	O
as	O
opposed	O
to	O
the	O
also	O
proposed	O
COFDM	B-Protocol
modulation	O
(	O
used	O
in	O
European	O
DVB-T	O
,	O
which	O
is	O
less	O
prone	O
to	O
multipath	O
distortion	O
and	O
therefore	O
better	O
received	O
in	O
mobile	O
installations	O
)	O
.	O
</s>
<s>
By	O
the	O
reverse	O
process	O
(	O
demultiplexing	B-Architecture
)	O
,	O
an	O
ATSC	B-Device
receiver	I-Device
first	O
receives	O
the	O
combined	O
MPEG	O
transport	O
stream	O
and	O
then	O
decodes	O
it	O
to	O
display	O
one	O
of	O
its	O
component	O
signals	O
on	O
a	O
TV	O
set	O
.	O
</s>
<s>
Since	O
digital	O
signals	O
that	O
are	O
broadcast	O
over	O
the	O
air	O
are	O
compressed	O
(	O
packed	O
smaller	O
)	O
,	O
once	O
they	O
are	O
received	O
by	O
the	O
ATSC	B-Device
tuner	I-Device
,	O
these	O
compressed	O
packets	O
of	O
digital	O
data	O
are	O
then	O
decompressed	B-General_Concept
(	O
unpacked	O
to	O
their	O
original	O
size	O
)	O
.	O
</s>
<s>
The	O
ATSC	B-Device
system	I-Device
uses	O
lossy	B-Algorithm
compression	I-Algorithm
,	O
so	O
while	O
the	O
decompressed	B-General_Concept
data	O
size	O
is	O
the	O
same	O
as	O
the	O
original	O
compressed	B-General_Concept
data	I-General_Concept
size	O
,	O
the	O
data	O
produced	O
is	O
not	O
exactly	O
the	O
same	O
as	O
the	O
original	O
data	O
fed	O
into	O
the	O
system	O
at	O
the	O
transmitting	O
site	O
,	O
but	O
it	O
is	O
close	O
enough	O
that	O
most	O
people	O
will	O
not	O
notice	O
a	O
difference	O
.	O
</s>
<s>
Error	B-Error_Name
correction	I-Error_Name
is	O
a	O
technology	O
that	O
is	O
used	O
by	O
the	O
ATSC	B-Device
tuner	I-Device
to	O
make	O
sure	O
that	O
any	O
data	O
that	O
is	O
missing	O
can	O
be	O
corrected	O
.	O
</s>
<s>
For	O
instance	O
,	O
sometimes	O
interference	O
or	O
a	O
poor-quality	O
signal	O
will	O
cause	O
the	O
loss	O
of	O
some	O
data	O
that	O
the	O
ATSC	B-Device
tuner	I-Device
receives	O
.	O
</s>
<s>
With	O
error	B-Error_Name
correction	I-Error_Name
,	O
the	O
tuner	B-Device
has	O
the	O
ability	O
to	O
perform	O
a	O
number	O
of	O
checks	O
and	O
repair	O
data	O
so	O
that	O
a	O
signal	O
can	O
be	O
viewed	O
on	O
a	O
TV	O
set	O
.	O
</s>
<s>
Error	B-Error_Name
correction	I-Error_Name
works	O
by	O
adding	O
some	O
extra	O
information	O
to	O
the	O
signal	O
before	O
transmission	O
that	O
can	O
be	O
used	O
upon	O
reception	O
to	O
fill	O
in	O
gaps	O
.	O
</s>
<s>
Therefore	O
,	O
error	B-Error_Name
correction	I-Error_Name
has	O
the	O
opposite	O
effect	O
of	O
compression	O
—	O
it	O
increases	O
the	O
amount	O
of	O
data	O
to	O
transmit	O
,	O
rather	O
than	O
reducing	O
it	O
like	O
compression	O
does	O
,	O
and	O
it	O
improves	O
the	O
quality	O
and	O
robustness	O
of	O
the	O
signal	O
rather	O
than	O
reducing	O
it	O
.	O
</s>
<s>
Compression	O
removes	O
redundant	O
(	O
and	O
some	O
non-redundant	O
)	O
data	O
,	O
while	O
error	B-Error_Name
correction	I-Error_Name
adds	O
some	O
redundant	O
data	O
.	O
</s>
<s>
The	O
reason	O
for	O
using	O
error	B-Error_Name
correction	I-Error_Name
rather	O
than	O
just	O
using	O
less	O
compression	O
and	O
keeping	O
the	O
redundancy	O
that	O
was	O
already	O
there	O
is	O
that	O
error	B-Error_Name
correction	I-Error_Name
systems	O
are	O
specially	O
designed	O
to	O
get	O
the	O
maximum	O
benefit	O
out	O
of	O
a	O
very	O
small	O
amount	O
of	O
redundant	O
data	O
,	O
whereas	O
the	O
natural	O
redundancy	O
of	O
the	O
data	O
does	O
n't	O
do	O
this	O
job	O
as	O
efficiently	O
,	O
so	O
with	O
error	B-Error_Name
correction	I-Error_Name
the	O
net	O
amount	O
of	O
data	O
needed	O
is	O
still	O
smaller	O
.	O
</s>
<s>
The	O
ATSC	B-Device
standard	I-Device
(	O
ATSC-E	O
)	O
has	O
a	O
subsection	O
that	O
allows	O
broadcasters	O
to	O
add	O
extra	O
(	O
and	O
variable	O
types	O
)	O
of	O
error	B-Error_Name
correction	I-Error_Name
to	O
their	O
broadcast	O
streams	O
.	O
</s>
<s>
This	O
error	B-Error_Name
correction	I-Error_Name
service	O
is	O
not	O
mandatory	O
in	O
the	O
US	O
,	O
nor	O
is	O
it	O
mandatory	O
in	O
Canada	O
.	O
</s>
<s>
It	O
is	O
not	O
known	O
how	O
many	O
HDTV	B-Device
receivers	I-Device
support	O
this	O
error	B-Error_Name
correction	I-Error_Name
standard	O
.	O
</s>
<s>
For	O
the	O
transmission	O
of	O
HDTV	B-Device
at	O
720	O
or	O
1080	O
,	O
an	O
extra	O
1%	O
to	O
3%	O
added	O
error	B-Error_Name
correction	I-Error_Name
codes	O
will	O
help	O
reduce	O
some	O
of	O
ATSC	B-Device
's	O
poorer	O
performance	O
with	O
weak	O
signals	O
under	O
adverse	O
multipath	O
conditions	O
.	O
</s>
<s>
Reception	O
is	O
greatly	O
reduced	O
due	O
to	O
EMI	O
in	O
the	O
shortwave	O
to	O
VHF	O
and	O
UHF	O
bandwidth	O
from	O
nearby	O
computers	O
of	O
all	O
sorts	O
[light],	O
portable	O
WiFi	O
and	O
Broadband	O
internet	O
[	O
medium	O
to	O
strong ]	O
,	O
microwave	O
ovens	O
[	O
burst	O
while	O
activated ]	O
,	O
cell	O
phones	O
and	O
the	O
towers	O
they	O
communicate	O
with	O
,	O
and	O
even	O
power	O
lines	O
with	O
electronic	B-Device
transmissions	I-Device
.	O
</s>
<s>
AV	B-Protocol
synchronization	I-Protocol
is	O
the	O
coordination	O
of	O
audio	O
and	O
video	O
signals	O
being	O
displayed	O
on	O
a	O
digital	B-Application
TV	I-Application
in	O
proper	O
time	O
.	O
</s>
<s>
AV	B-Protocol
synchronization	I-Protocol
ensures	O
that	O
the	O
audio	O
does	O
not	O
lag	O
behind	O
the	O
video	O
that	O
is	O
being	O
displayed	O
on	O
the	O
TV	O
set	O
or	O
vice	O
versa	O
,	O
so	O
that	O
both	O
audio	O
and	O
video	O
are	O
in	O
sync	O
.	O
</s>
<s>
For	O
instance	O
,	O
some	O
televisions	O
have	O
an	O
interlaced	O
picture	O
,	O
whereas	O
others	O
have	O
a	O
progressive-scan	B-Device
picture	O
.	O
</s>
<s>
Different	O
televisions	O
have	O
a	O
different	O
aspect	B-General_Concept
ratio	I-General_Concept
.	O
</s>
<s>
By	O
July	O
1	O
,	O
2005	O
all	O
televisions	O
with	O
screen	O
sizes	O
over	O
must	O
include	O
a	O
built-in	O
ATSC	B-Device
DTV	B-Device
tuner	I-Device
.	O
</s>
<s>
By	O
March	O
1	O
,	O
2006	O
all	O
televisions	O
with	O
screen	O
sizes	O
over	O
must	O
include	O
a	O
built-in	O
ATSC	B-Device
DTV	B-Device
tuner	I-Device
.	O
</s>
<s>
By	O
March	O
1	O
,	O
2007	O
all	O
televisions	O
regardless	O
of	O
screen	O
size	O
,	O
and	O
all	O
interface	O
devices	O
that	O
include	O
a	O
tuner	B-Device
(	O
VCR	O
,	O
DVD	O
player/recorder	O
,	O
DVR	O
)	O
must	O
include	O
a	O
built-in	O
ATSC	B-Device
DTV	B-Device
tuner	I-Device
.	O
</s>
<s>
Devices	O
manufactured	O
before	O
these	O
dates	O
can	O
still	O
be	O
sold	O
without	O
a	O
built-in	O
ATSC	B-Device
DTV	B-Device
tuner	I-Device
;	O
the	O
lack	O
of	O
digital	B-Device
tuners	I-Device
legally	O
must	O
be	O
disclosed	O
to	O
consumers	O
and	O
most	O
name-brand	O
retailers	O
have	O
incurred	O
FCC	O
penalties	O
for	O
non-compliance	O
with	O
these	O
requirements	O
.	O
</s>
<s>
As	O
of	O
June	O
12	O
,	O
2009	O
,	O
TVs	O
and	O
other	O
equipment	O
with	O
legacy	O
NTSC	O
tuners	B-Device
are	O
unable	O
to	O
receive	O
over-the-air	O
broadcasts	O
from	O
United	O
States	O
TV	O
stations	O
,	O
unless	O
the	O
broadcast	O
is	O
from	O
a	O
repeater	O
or	O
low-power	O
transmitter	O
.	O
</s>
<s>
Viewers	O
who	O
did	O
not	O
upgrade	O
,	O
either	O
to	O
a	O
television	O
with	O
a	O
digital	B-Device
tuner	I-Device
or	O
a	O
set-top	O
box	O
,	O
ended	O
up	O
losing	O
their	O
only	O
source	O
of	O
television	O
,	O
unless	O
they	O
relied	O
only	O
upon	O
the	O
aforementioned	O
non-full-power	O
broadcasters	O
.	O
</s>
<s>
Unlike	O
in	O
the	O
United	O
States	O
,	O
there	O
is	O
no	O
plan	O
to	O
subsidise	O
ATSC	B-Device
converter	O
purchases	O
and	O
no	O
requirement	O
that	O
newly	O
imported	O
receivers	B-Device
decode	O
the	O
digital	O
signal	O
.	O
</s>
<s>
A	O
limited	O
number	O
of	O
ATSC	B-Device
receivers	I-Device
are	O
in	O
Canadian	O
retail	O
stores	O
as	O
high-definition	B-Device
television	I-Device
(	O
HDTV	B-Device
)	O
receivers	B-Device
.	O
</s>
<s>
ATSC	B-Device
CECB	O
converter	O
boxes	O
were	O
first	O
carried	O
nationally	O
in	O
October	O
2008	O
,	O
with	O
chains	O
such	O
as	O
Best	O
Buy	O
and	O
Home	O
Hardware	O
offering	O
limited	O
selection	O
at	O
higher	O
prices	O
than	O
in	O
the	O
US	O
with	O
no	O
government	O
subsidies	O
.	O
</s>
<s>
ATSC	B-Device
tuners	I-Device
may	O
also	O
be	O
present	O
in	O
most	O
recently	O
manufactured	O
televisions	O
,	O
as	O
well	O
as	O
DVD	O
recorders	O
,	O
HDTV	B-Device
FTA	O
receivers	B-Device
,	O
and	O
personal	B-Device
computer	I-Device
TV	B-Device
tuner	I-Device
cards	I-Device
.	O
</s>
<s>
As	O
of	O
the	O
beginning	O
of	O
2012	O
,	O
almost	O
all	O
Canadian	O
broadcasters	O
are	O
broadcasting	O
an	O
ATSC	B-Device
signal	O
,	O
with	O
a	O
handful	O
of	O
exceptions	O
granted	O
for	O
low-power	O
and	O
regional	O
stations	O
.	O
</s>
<s>
These	O
signals	O
can	O
be	O
reliably	O
tuned	O
in	O
most	O
cities	O
with	O
a	O
good	O
indoor	O
antenna	O
and	O
an	O
ATSC	B-Device
tuner	I-Device
.	O
</s>
<s>
US-based	O
ATSC	B-Device
signals	O
can	O
be	O
reliably	O
tuned	O
with	O
an	O
outdoor	O
antenna	O
and	O
an	O
ATSC	B-Device
tuner	I-Device
in	O
Canadian	O
markets	O
within	O
60	O
miles	O
of	O
the	O
US	O
broadcast	O
towers	O
.	O
</s>
<s>
Most	O
ATSC	B-Device
tuners	I-Device
have	O
relatively	O
simple	O
on-screen	O
menus	O
,	O
and	O
automatically	O
bring	O
the	O
user	O
to	O
a	O
setup	O
screen	O
when	O
turned	O
on	O
for	O
the	O
first	O
time	O
.	O
</s>
<s>
This	O
allows	O
the	O
user	O
to	O
pick	O
the	O
time	B-Device
zone	I-Device
and	O
daylight-saving	O
time	O
mode	O
(	O
as	O
all	O
stations	O
transmit	O
time	O
in	O
UTC	O
)	O
,	O
and	O
bandscan	O
for	O
stations	O
.	O
</s>
<s>
If	O
it	O
is	O
able	O
to	O
decode	O
the	O
station	O
,	O
it	O
reads	O
its	O
PSIP	B-Device
data	O
,	O
and	O
adds	O
its	O
virtual	B-Protocol
channels	I-Protocol
to	O
the	O
channel	O
map	O
.	O
</s>
<s>
If	O
no	O
PSIP	B-Device
is	O
transmitted	O
,	O
the	O
physical	O
channel	O
number	O
is	O
used	O
,	O
and	O
each	O
transport	O
stream	O
is	O
enumerated	B-Language
according	O
to	O
its	O
TSID	O
(	O
converted	O
from	O
hexadecimal	O
)	O
,	O
or	O
starting	O
sequentially	O
at	O
.1	O
,	O
.2	O
,	O
.3	O
,	O
and	O
so	O
forth	O
,	O
depending	O
on	O
the	O
tuner	B-Device
.	O
</s>
<s>
Several	O
TV	O
stations	O
are	O
using	O
or	O
have	O
used	O
a	O
temporary	O
channel	O
to	O
send	O
their	O
DTV	O
signals	O
and	O
,	O
upon	O
terminating	O
analog	O
transmission	O
,	O
move	O
their	O
digital	O
transmission	O
either	O
back	O
to	O
their	O
old	O
analog	O
channel	O
,	O
or	O
to	O
a	O
third	O
channel	O
(	O
sometimes	O
the	O
former	O
analog	O
of	O
another	O
local	O
station	O
)	O
,	O
chosen	O
in	O
the	O
digital	B-Device
channel	I-Device
election	I-Device
in	O
the	O
U.S.	O
</s>
<s>
Doing	O
a	O
full	O
re-scan	O
will	O
usually	O
cause	O
other	O
channels	O
to	O
be	O
dropped	O
if	O
they	O
cannot	O
be	O
received	O
at	O
the	O
moment	O
the	O
scan	O
passes	O
their	O
physical	O
channel	O
,	O
so	O
this	O
is	O
typically	O
undesirable	O
,	O
although	O
many	O
ATSC	B-Device
tuners	I-Device
only	O
have	O
this	O
option	O
.	O
</s>
<s>
Some	O
allow	O
the	O
user	O
to	O
enter	O
the	O
physical	O
channel	O
and	O
an	O
unmapped	O
subchannel	B-Device
,	O
causing	O
the	O
tuner	B-Device
to	O
search	O
the	O
physical	O
channel	O
.	O
</s>
<s>
Depending	O
on	O
the	O
tuner	B-Device
,	O
this	O
may	O
or	O
may	O
not	O
automatically	O
add	O
the	O
station	O
and	O
its	O
digital	B-Device
subchannels	I-Device
to	O
the	O
map	O
,	O
and/or	O
to	O
the	O
user	O
's	O
"	O
favorites	O
"	O
.	O
</s>
<s>
If	O
the	O
auto	O
scan	O
does	O
not	O
pick	O
up	O
the	O
signal	O
and	O
the	O
tuner	B-Device
has	O
manual	O
frequency	O
scan	O
capability	O
try	O
to	O
get	O
the	O
actual	O
frequency	O
from	O
the	O
station	O
engineer	O
.	O
</s>
<s>
Other	O
errors	O
which	O
appear	O
to	O
be	O
in	O
the	O
tuner	B-Device
are	O
actually	O
the	O
result	O
of	O
incorrect	O
data	O
sent	O
by	O
one	O
or	O
more	O
stations	O
,	O
often	O
including	O
missing	O
electronic	B-Device
program	I-Device
guide	I-Device
data	O
.	O
</s>
<s>
Many	O
ATSC	B-Device
tuners	I-Device
will	O
remember	O
EPG	B-Device
info	O
for	O
each	O
station	O
,	O
but	O
only	O
for	O
a	O
few	O
hours	O
after	O
viewing	O
a	O
channel	O
on	O
that	O
station	O
.	O
</s>
<s>
DirecTV	O
receivers	B-Device
with	O
ATSC	B-Device
tuners	I-Device
can	O
download	O
the	O
guide	O
at	O
any	O
time	O
,	O
while	O
other	O
TiVo	B-Application
units	O
download	O
guide	O
data	O
separately	O
.	O
</s>
<s>
TV	B-Device
Guide	I-Device
On	I-Device
Screen	I-Device
can	O
also	O
be	O
used	O
for	O
this	O
,	O
but	O
very	O
few	O
if	O
any	O
ATSC	B-Device
tuners	I-Device
include	O
this	O
(	O
which	O
requires	O
downloading	O
all	O
guide	O
data	O
for	O
all	O
channels	O
from	O
one	O
particular	O
station	O
)	O
.	O
</s>
<s>
Each	O
digital	O
OTA	O
channel	O
number	O
is	O
composed	O
of	O
a	O
main	O
number	O
and	O
a	O
subchannel	B-Device
,	O
for	O
example	O
4.1	O
,	O
4.2	O
,	O
etc	O
.	O
</s>
<s>
However	O
,	O
now	O
"	O
virtual	B-Protocol
channel	I-Protocol
"	O
(	O
technically	O
known	O
as	O
logical	O
channel	O
number	O
)	O
numbers	O
are	O
common	O
.	O
</s>
<s>
When	O
the	O
ATSC	B-Device
tuner	I-Device
does	O
a	O
channel	O
scan	O
,	O
it	O
finds	O
the	O
signal	O
on	O
channel	O
43	O
,	O
learns	O
that	O
this	O
material	O
is	O
called	O
"	O
Channel	O
4	O
"	O
,	O
and	O
remembers	O
that	O
mapping	O
.	O
</s>
<s>
The	O
user	O
can	O
tune	O
to	O
"	O
4	O
"	O
,	O
and	O
the	O
tuner	B-Device
will	O
know	O
to	O
tune	B-Device
in	I-Device
43	O
.	O
</s>
