<s>
A	O
wireless	B-Device
microphone	I-Device
,	O
or	O
cordless	B-Device
microphone	I-Device
,	O
is	O
a	O
microphone	B-Application
without	O
a	O
physical	O
cable	O
connecting	O
it	O
directly	O
to	O
the	O
sound	O
recording	O
or	O
amplifying	O
equipment	O
with	O
which	O
it	O
is	O
associated	O
.	O
</s>
<s>
Also	O
known	O
as	O
a	O
radio	B-Device
microphone	I-Device
,	O
it	O
has	O
a	O
small	O
,	O
battery-powered	O
radio	O
transmitter	O
in	O
the	O
microphone	B-Application
body	O
,	O
which	O
transmits	O
the	O
audio	O
signal	O
from	O
the	O
microphone	B-Application
by	O
radio	O
waves	O
to	O
a	O
nearby	O
receiver	O
unit	O
,	O
which	O
recovers	O
the	O
audio	O
.	O
</s>
<s>
In	O
one	O
type	O
the	O
transmitter	O
is	O
contained	O
within	O
the	O
handheld	O
microphone	B-Application
body	O
.	O
</s>
<s>
The	O
bodypack	O
is	O
connected	O
by	O
wire	O
to	O
a	O
"	O
lavalier	B-Algorithm
microphone	I-Algorithm
"	O
or	O
"	O
lav	O
"	O
(	O
a	O
small	O
microphone	B-Application
clipped	O
to	O
the	O
user	O
's	O
lapel	O
)	O
,	O
a	O
headset	B-Device
or	O
earset	O
microphone	B-Application
,	O
or	O
another	O
wired	O
microphone	B-Application
.	O
</s>
<s>
Wireless	B-Device
microphones	I-Device
are	O
widely	O
used	O
in	O
the	O
entertainment	O
industry	O
,	O
television	O
broadcasting	O
,	O
and	O
public	O
speaking	O
to	O
allow	O
public	O
speakers	O
,	O
interviewers	O
,	O
performers	O
,	O
and	O
entertainers	O
to	O
move	O
about	O
freely	O
while	O
using	O
a	O
microphone	B-Application
without	O
requiring	O
a	O
cable	O
attached	O
to	O
the	O
microphone	B-Application
.	O
</s>
<s>
Wireless	B-Device
microphones	I-Device
usually	O
use	O
the	O
VHF	B-Algorithm
or	O
UHF	O
frequency	O
bands	O
since	O
they	O
allow	O
the	O
transmitter	O
to	O
use	O
a	O
small	O
unobtrusive	O
antenna	O
.	O
</s>
<s>
Cheap	O
units	O
use	O
a	O
fixed	O
frequency	O
but	O
most	O
units	O
allow	O
a	O
choice	O
of	O
several	O
frequency	O
channels	O
,	O
in	O
case	O
of	O
interference	O
on	O
a	O
channel	O
or	O
to	O
allow	O
the	O
use	O
of	O
multiple	O
microphones	B-Application
at	O
the	O
same	O
time	O
.	O
</s>
<s>
FM	B-Application
modulation	B-Application
is	O
usually	O
used	O
,	O
although	O
some	O
models	O
use	O
digital	O
modulation	B-Application
to	O
prevent	O
unauthorized	O
reception	O
by	O
scanner	O
radio	O
receivers	O
;	O
these	O
operate	O
in	O
the	O
900MHz	O
,	O
2.4GHz	B-Algorithm
or	O
6GHz	O
ISM	B-Algorithm
bands	I-Algorithm
.	O
</s>
<s>
A	O
few	O
low	O
cost	O
(	O
or	O
specialist	O
)	O
models	O
use	O
infrared	O
light	O
,	O
although	O
these	O
require	O
a	O
direct	O
line	O
of	O
sight	O
between	O
microphone	B-Application
and	O
receiver	O
.	O
</s>
<s>
Various	O
individuals	O
and	O
organizations	O
claim	O
to	O
be	O
the	O
inventors	O
of	O
the	O
wireless	B-Device
microphone	I-Device
.	O
</s>
<s>
From	O
about	O
1945	O
there	O
were	O
schematics	O
and	O
hobbyist	O
kits	O
offered	O
in	O
Popular	O
Science	O
and	O
Popular	O
Mechanics	O
for	O
making	O
a	O
wireless	B-Device
microphone	I-Device
that	O
would	O
transmit	O
the	O
voice	O
to	O
a	O
nearby	O
radio	O
.	O
</s>
<s>
Figure	O
skater	O
and	O
Royal	O
Air	O
Force	O
flight	O
engineer	O
Reg	O
Moores	O
developed	O
a	O
radio	B-Device
microphone	I-Device
in	O
1947	O
that	O
he	O
first	O
used	O
in	O
the	O
Tom	O
Arnold	O
production	O
"	O
Aladdin	O
on	O
Ice	O
"	O
at	O
Brighton	O
's	O
sports	O
stadium	O
from	O
September	O
1949	O
through	O
the	O
Christmas	O
season	O
.	O
</s>
<s>
The	O
producers	O
of	O
the	O
ice	O
show	O
decided	O
that	O
they	O
would	O
not	O
continue	O
using	O
the	O
device	O
;	O
they	O
would	O
rather	O
hire	O
actors	O
and	O
singers	O
to	O
perform	O
into	O
hidden	O
microphones	B-Application
to	O
"	O
dub	O
"	O
the	O
voices	O
of	O
the	O
other	O
ice	O
skaters	O
,	O
who	O
would	O
thus	O
be	O
free	O
to	O
concentrate	O
on	O
their	O
skating	O
.	O
</s>
<s>
Herbert	O
"	O
Mac	O
"	O
McClelland	O
,	O
founder	O
of	O
McClelland	O
Sound	O
in	O
Wichita	O
,	O
Kansas	O
,	O
fabricated	O
a	O
wireless	B-Device
microphone	I-Device
to	O
be	O
worn	O
by	O
baseball	O
umpires	O
at	O
major	O
league	O
games	O
broadcast	O
by	O
NBC	O
from	O
Lawrence	O
–	O
Dumont	O
Stadium	O
in	O
1951	O
.	O
</s>
<s>
Shure	O
Brothers	O
claims	O
that	O
its	O
"	O
Vagabond	O
"	O
system	O
from	O
1953	O
was	O
the	O
first	O
"	O
wireless	B-Device
microphone	I-Device
system	O
for	O
performers.	O
"	O
</s>
<s>
In	O
1957	O
,	O
the	O
German	O
audio	O
equipment	O
manufacturer	O
Sennheiser	O
,	O
at	O
that	O
time	O
called	O
Lab	O
W	O
,	O
working	O
with	O
the	O
German	O
broadcaster	O
Norddeutscher	O
Rundfunk	O
(	O
NDR	O
)	O
,	O
exhibited	O
a	O
wireless	B-Device
microphone	I-Device
system	O
.	O
</s>
<s>
The	O
pocket-sized	O
Mikroport	O
incorporated	O
a	O
dynamic	O
moving-coil	O
cartridge	O
microphone	B-Application
with	O
a	O
cardioid	O
pickup	O
pattern	O
.	O
</s>
<s>
The	O
first	O
recorded	O
patent	O
for	O
a	O
wireless	B-Device
microphone	I-Device
was	O
filed	O
by	O
Raymond	O
A	O
.	O
Litke	O
,	O
an	O
American	O
electrical	O
engineer	O
with	O
Educational	O
Media	O
Resources	O
and	O
San	O
Jose	O
State	O
College	O
,	O
who	O
invented	O
a	O
wireless	B-Device
microphone	I-Device
in	O
1957	O
to	O
meet	O
the	O
multimedia	O
needs	O
for	O
television	O
,	O
radio	O
,	O
and	O
classroom	O
instruction	O
.	O
</s>
<s>
Two	O
microphone	B-Application
types	O
were	O
made	O
available	O
for	O
purchase	O
in	O
1959	O
:	O
hand-held	O
and	O
lavalier	O
.	O
</s>
<s>
Introduced	O
in	O
1958	O
,	O
the	O
Sony	O
CR-4	O
wireless	B-Device
microphone	I-Device
was	O
being	O
recommended	O
as	O
early	O
as	O
1960	O
for	O
theatre	O
performances	O
and	O
nightclub	O
acts	O
.	O
</s>
<s>
The	O
27.12MHz	O
solid-state	O
FM	B-Application
transmitter	O
was	O
capable	O
of	O
fitting	O
into	O
a	O
shirt	O
pocket	O
.	O
</s>
<s>
Said	O
to	O
be	O
effective	O
out	O
to	O
,	O
it	O
mounted	O
a	O
flexible	O
dangling	O
antenna	O
and	O
a	O
detachable	O
dynamic	O
microphone	B-Application
.	O
</s>
<s>
Another	O
German	O
equipment	O
manufacturer	O
,	O
Beyerdynamic	O
,	O
claims	O
that	O
the	O
first	O
wireless	B-Device
microphone	I-Device
was	O
invented	O
by	O
Hung	O
C	O
.	O
Lin	O
.	O
</s>
<s>
The	O
first	O
time	O
that	O
a	O
wireless	B-Device
microphone	I-Device
was	O
used	O
to	O
record	O
sound	O
during	O
filming	O
of	O
a	O
motion	O
picture	O
was	O
allegedly	O
on	O
Rex	O
Harrison	O
in	O
the	O
1964	O
film	O
My	O
Fair	O
Lady	O
,	O
through	O
the	O
efforts	O
of	O
Academy	O
Award-winning	O
Hollywood	O
sound	O
engineer	O
George	O
Groves	O
.	O
</s>
<s>
Wider	O
dynamic	O
range	O
came	O
with	O
the	O
introduction	O
of	O
the	O
first	O
compander	B-Algorithm
wireless	B-Device
microphone	I-Device
,	O
offered	O
by	O
Nady	O
Systems	O
in	O
1976	O
.	O
</s>
<s>
Kate	O
Bush	O
is	O
regarded	O
as	O
the	O
first	O
artist	O
to	O
have	O
had	O
a	O
headset	B-Device
with	O
a	O
wireless	B-Device
microphone	I-Device
built	O
for	O
use	O
in	O
music	O
.	O
</s>
<s>
For	O
her	O
Tour	O
of	O
Life	O
in	O
1979	O
she	O
had	O
a	O
compact	O
microphone	B-Application
combined	O
with	O
a	O
self-made	O
construction	O
of	O
wire	O
clothes	O
hangers	O
,	O
to	O
free	O
her	O
hands	O
for	O
expressionist	O
dance	O
performances	O
.	O
</s>
<s>
Nady	O
joined	O
CBS	O
,	O
Sennheiser	O
and	O
Vega	O
in	O
1996	O
to	O
receive	O
a	O
joint	O
Emmy	O
Award	O
for	O
"	O
pioneering	O
 [ the ] 	O
development	O
of	O
the	O
broadcast	O
wireless	B-Device
microphone	I-Device
"	O
.	O
</s>
<s>
Sometimes	O
limited	O
range	O
(	O
a	O
wired	O
balanced	O
XLR	O
microphone	B-Application
can	O
run	O
up	O
to	O
300ft	O
or	O
100	O
meters	O
)	O
.	O
</s>
<s>
Possible	O
interference	O
with	O
or	O
,	O
more	O
often	O
,	O
from	O
other	O
radio	O
equipment	O
or	O
other	O
radio	B-Device
microphones	I-Device
,	O
though	O
models	O
with	O
many	O
frequency-synthesized	O
switch-selectable	O
channels	O
are	O
now	O
plentiful	O
and	O
cost	O
effective	O
.	O
</s>
<s>
Operation	O
time	O
is	O
limited	O
relative	O
to	O
battery	O
life	O
;	O
it	O
is	O
shorter	O
than	O
a	O
normal	O
condenser	O
microphone	B-Application
due	O
to	O
greater	O
drain	O
on	O
batteries	O
from	O
transmitting	O
circuitry	O
,	O
and	O
from	O
circuitry	O
giving	O
extra	O
features	O
,	O
if	O
present	O
.	O
</s>
<s>
Limited	O
number	O
of	O
operating	O
microphones	B-Application
at	O
the	O
same	O
time	O
and	O
place	O
,	O
due	O
to	O
the	O
limited	O
number	O
of	O
radio	O
channels	O
(	O
frequencies	O
)	O
.	O
</s>
<s>
The	O
professional	O
models	O
transmit	O
in	O
VHF	B-Algorithm
or	O
UHF	O
radio	O
frequency	O
and	O
have	O
'	O
true	O
 '	O
diversity	B-Protocol
reception	I-Protocol
(	O
two	O
separate	O
receiver	O
modules	O
,	O
each	O
with	O
its	O
own	O
antenna	O
)	O
,	O
which	O
eliminates	O
dead	O
spots	O
(	O
caused	O
by	O
phase	O
cancellation	O
)	O
and	O
the	O
effects	O
caused	O
by	O
the	O
reflection	O
of	O
the	O
radio	O
waves	O
on	O
walls	O
and	O
surfaces	O
in	O
general	O
.	O
</s>
<s>
Another	O
technique	O
used	O
to	O
improve	O
the	O
sound	O
quality	O
(	O
actually	O
,	O
to	O
improve	O
the	O
dynamic	O
range	O
)	O
,	O
is	O
companding	B-Algorithm
.	O
</s>
<s>
Nady	O
Systems	O
,	O
Inc	O
.	O
was	O
the	O
first	O
to	O
offer	O
this	O
technology	O
in	O
wireless	B-Device
microphones	I-Device
in	O
1976	O
,	O
which	O
was	O
based	O
on	O
the	O
patent	O
obtained	O
by	O
company	O
founder	O
John	O
Nady	O
.	O
</s>
<s>
Some	O
models	O
have	O
adjustable	O
gain	O
on	O
the	O
microphone	B-Application
itself	O
to	O
be	O
able	O
to	O
accommodate	O
different	O
level	O
sources	O
,	O
such	O
as	O
loud	O
instruments	O
or	O
quiet	O
voices	O
.	O
</s>
<s>
Some	O
models	O
have	O
adjustable	O
squelch	O
,	O
which	O
silences	O
the	O
output	O
when	O
the	O
receiver	O
does	O
not	O
get	O
a	O
strong	O
or	O
quality	O
signal	O
from	O
the	O
microphone	B-Application
,	O
instead	O
of	O
reproducing	O
noise	O
.	O
</s>
<s>
AKG	O
Acoustics	O
,	O
Audio	O
Ltd	O
,	O
Audio-Technica	O
,	O
Electro-Voice	O
,	O
Lectrosonics	O
,	O
MIPRO	O
,	O
Nady	O
Systems	O
,	O
Inc	O
,	O
Samson	O
Technologies	O
,	O
Sennheiser	O
,	O
Shure	O
,	O
Sony	O
,	O
Wisycom	O
and	O
Zaxcom	O
are	O
all	O
major	O
manufacturers	O
of	O
wireless	B-Device
microphone	I-Device
systems	O
.	O
</s>
<s>
For	O
example	O
,	O
while	O
there	O
is	O
a	O
limited	O
band	O
in	O
which	O
the	O
microphones	B-Application
may	O
operate	O
,	O
several	O
high-end	O
systems	O
can	O
consist	O
of	O
over	O
100	O
different	O
microphones	B-Application
operating	O
simultaneously	O
.	O
</s>
<s>
However	O
,	O
the	O
ability	O
to	O
have	O
more	O
microphones	B-Application
operating	O
at	O
the	O
same	O
time	O
increases	O
the	O
cost	O
due	O
to	O
component	O
specifications	O
,	O
design	O
and	O
construction	O
.	O
</s>
<s>
Generally	O
there	O
are	O
three	O
wireless	B-Device
microphone	I-Device
types	O
:	O
handheld	O
,	O
plug-in	O
and	O
bodypack	O
:	O
</s>
<s>
Handheld	O
looks	O
like	O
a	O
'	O
normal	O
 '	O
wired	O
microphone	B-Application
,	O
may	O
have	O
a	O
bigger	O
body	O
to	O
accommodate	O
the	O
transmitter	O
and	O
battery	O
pack	O
.	O
</s>
<s>
Plug-in	O
,	O
plug-on	O
,	O
slot-in	O
,	O
or	O
cube-style	O
transmitters	O
attach	O
to	O
the	O
bottom	O
of	O
a	O
standard	O
microphone	B-Application
,	O
thus	O
converting	O
it	O
to	O
wireless	O
operation	O
(	O
see	O
below	O
)	O
.	O
</s>
<s>
Bodypack	O
is	O
a	O
small	O
box	O
housing	O
the	O
transmitter	O
and	O
battery	O
pack	O
,	O
but	O
not	O
the	O
microphone	B-Application
itself	O
.	O
</s>
<s>
It	O
is	O
attachable	O
to	O
clothing	O
or	O
on	O
the	O
body	O
and	O
has	O
a	O
wire	O
going	O
into	O
a	O
headset	B-Device
,	O
a	O
lavalier	B-Algorithm
microphone	I-Algorithm
or	O
a	O
guitar	O
.	O
</s>
<s>
Several	O
manufacturers	O
including	O
Sennheiser	O
,	O
AKG	O
,	O
Nady	O
Systems	O
,	O
Lectrosonics	O
and	O
Zaxcom	O
offer	O
a	O
plug-in	O
transmitter	O
for	O
existing	O
wired	O
microphones	B-Application
,	O
which	O
plugs	O
into	O
the	O
XLR	O
output	O
of	O
the	O
microphone	B-Application
and	O
transmits	O
to	O
the	O
manufacturer	O
's	O
standard	O
receiver	O
.	O
</s>
<s>
This	O
offers	O
many	O
of	O
the	O
benefits	O
of	O
an	O
integrated	O
system	O
,	O
and	O
also	O
allows	O
microphone	B-Application
types	O
(	O
of	O
which	O
there	O
may	O
be	O
no	O
wireless	O
equivalent	O
)	O
to	O
be	O
used	O
without	O
a	O
cable	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
television	O
,	O
or	O
film	O
,	O
sound	O
production	O
engineer	O
may	O
use	O
a	O
plug-in	O
transmitter	O
to	O
enable	O
wireless	O
transmission	O
of	O
a	O
highly	O
directional	O
rifle	O
(	O
or	O
"	O
shotgun	O
"	O
)	O
microphone	B-Application
,	O
removing	O
the	O
safety	O
hazard	O
of	O
a	O
cable	O
connection	O
and	O
permitting	O
the	O
production	O
engineer	O
greater	O
freedom	O
to	O
follow	O
the	O
action	O
.	O
</s>
<s>
Plug-in	O
transmitters	O
also	O
allow	O
the	O
conversion	O
of	O
vintage	O
microphone	B-Application
types	O
to	O
cordless	O
operation	O
.	O
</s>
<s>
This	O
is	O
useful	O
where	O
a	O
vintage	O
microphone	B-Application
is	O
needed	O
for	O
visual	O
or	O
other	O
artistic	O
reasons	O
,	O
and	O
the	O
absence	O
of	O
cables	O
allows	O
for	O
rapid	O
scene	O
changes	O
and	O
reducing	O
trip	O
hazards	O
.	O
</s>
<s>
In	O
some	O
cases	O
these	O
plug-in	O
transmitters	O
can	O
also	O
provide	O
48	O
volt	O
phantom	B-Algorithm
power	I-Algorithm
allowing	O
the	O
use	O
of	O
condenser	O
microphone	B-Application
types	O
.	O
</s>
<s>
For	O
large	O
complex	O
multi	O
channel	O
radio	B-Device
microphone	I-Device
systems	O
,	O
as	O
used	O
in	O
broadcast	O
television	O
studios	O
and	O
musical	O
theatre	O
productions	O
,	O
modular	O
receiver	O
systems	O
with	O
several	O
(	O
commonly	O
six	O
or	O
eight	O
)	O
true	O
diversity	O
receivers	O
slotting	O
into	O
a	O
rack-mounted	O
mainframe	O
housing	O
are	O
available	O
.	O
</s>
<s>
In	O
some	O
musical	O
theatre	O
productions	O
,	O
systems	O
with	O
forty	O
or	O
more	O
radio	B-Device
microphones	I-Device
are	O
not	O
unusual	O
.	O
</s>
<s>
Almost	O
all	O
wireless	B-Device
microphone	I-Device
systems	O
use	O
wide	O
band	O
FM	B-Application
modulation	B-Application
,	O
requiring	O
approximately	O
200kHz	O
of	O
bandwidth	O
.	O
</s>
<s>
Because	O
of	O
the	O
relatively	O
large	O
bandwidth	O
requirements	O
,	O
wireless	B-Device
microphone	I-Device
use	O
is	O
effectively	O
restricted	O
to	O
VHF	B-Algorithm
and	O
above	O
.	O
</s>
<s>
Many	O
older	O
wireless	B-Device
microphone	I-Device
systems	O
operate	O
in	O
the	O
VHF	B-Algorithm
part	O
of	O
the	O
electromagnetic	O
spectrum	O
.	O
</s>
<s>
Most	O
modern	O
wireless	B-Device
microphone	I-Device
products	O
operate	O
in	O
the	O
UHF	O
television	O
band	O
,	O
however	O
.	O
</s>
<s>
In	O
2010	O
the	O
Federal	O
Communications	O
Commission	O
issued	O
new	O
regulations	O
on	O
the	O
operations	O
of	O
TV-band	B-Algorithm
devices	I-Algorithm
.	O
</s>
<s>
Typically	O
,	O
wireless	B-Device
microphones	I-Device
operate	O
on	O
unused	O
TV	O
channels	O
(	O
"	O
white	O
spaces	O
"	O
)	O
,	O
with	O
room	O
for	O
one	O
to	O
two	O
microphones	B-Application
per	O
megahertz	O
of	O
spectrum	O
available	O
.	O
</s>
<s>
Digital	O
Hybrid	O
systems	O
use	O
an	O
analogue	O
FM	B-Application
transmission	O
scheme	O
in	O
combination	O
with	O
digital	B-General_Concept
signal	I-General_Concept
processing	I-General_Concept
(	O
DSP	O
)	O
to	O
enhance	O
the	O
system	O
's	O
audio	O
.	O
</s>
<s>
Another	O
approach	O
is	O
to	O
use	O
DSP	O
in	O
order	O
to	O
emulate	O
analogue	O
companding	B-Algorithm
schemes	O
in	O
order	O
to	O
maintain	O
compatibility	O
between	O
older	O
analogue	O
systems	O
and	O
newer	O
systems	O
.	O
</s>
<s>
A	O
number	O
of	O
pure	O
digital	O
wireless	B-Device
microphone	I-Device
systems	O
do	O
exist	O
,	O
and	O
there	O
are	O
many	O
different	O
digital	O
modulation	B-Application
schemes	O
possible	O
.	O
</s>
<s>
Digital	O
systems	O
from	O
Sennheiser	O
,	O
Sony	O
,	O
Shure	O
,	O
Zaxcom	O
,	O
AKG	O
and	O
MIPRO	O
use	O
the	O
same	O
UHF	O
frequencies	O
used	O
by	O
analogue	O
FM	B-Application
systems	O
for	O
transmission	O
of	O
a	O
digital	O
signal	O
at	O
a	O
fixed	O
bit	O
rate	O
.	O
</s>
<s>
Only	O
the	O
Sennheiser	O
Digital	O
9000	O
system	O
,	O
introduced	O
in	O
2013	O
,	O
is	O
currently	O
capable	O
of	O
transmitting	O
full-bandwidth	O
,	O
uncompressed	O
,	O
digital	O
audio	O
in	O
the	O
same	O
200kHz	O
bandwidth	O
UHF	O
channels	O
that	O
were	O
used	O
by	O
analogue	O
FM	B-Application
systems	O
.	O
</s>
<s>
Some	O
systems	O
use	O
frequency-hopping	B-Protocol
spread	I-Protocol
spectrum	I-Protocol
technology	O
,	O
similar	O
to	O
that	O
used	O
for	O
cordless	O
phones	O
and	O
radio-controlled	O
models	O
.	O
</s>
<s>
As	O
this	O
can	O
require	O
more	O
bandwidth	O
than	O
a	O
wideband	B-Application
FM	I-Application
signal	O
,	O
these	O
microphones	B-Application
typically	O
operate	O
in	O
the	O
unlicensed	O
900MHz	O
,	O
2.4GHz	B-Algorithm
or	O
6GHz	O
bands	O
.	O
</s>
<s>
The	O
2.4GHz	B-Algorithm
band	I-Algorithm
is	O
increasingly	O
congested	O
with	O
various	O
systems	O
including	O
WiFi	O
(	O
also	O
referred	O
to	O
as	O
Wireless	O
LAN	O
,	O
wireless	O
networks	O
,	O
802.11b/g/n	O
)	O
,	O
Bluetooth	O
and	O
'	O
leakage	O
 '	O
from	O
microwave	O
ovens	O
.	O
</s>
<s>
The	O
Alteros	O
GTX	O
Series	O
is	O
a	O
local	O
area	O
wireless	B-Device
microphone	I-Device
network	O
that	O
overcomes	O
the	O
line-of-sight	O
problem	O
by	O
utilizing	O
up	O
to	O
64	O
transceivers	O
around	O
the	O
performance	O
area	O
.	O
</s>
<s>
It	O
is	O
also	O
the	O
only	O
system	O
employing	O
Ultra	O
WideBand	O
pulsed	O
RF	O
technology	O
which	O
does	O
n't	O
generate	O
intermodulation	O
products	O
common	O
with	O
FM	B-Application
,	O
QAM	O
and	O
GFSK	O
modulated	B-Application
carriers	O
used	O
by	O
most	O
other	O
systems	O
.	O
</s>
<s>
Digital	O
radio	B-Device
microphones	I-Device
are	O
inherently	O
more	O
difficult	O
for	O
the	O
casual	O
'	O
scanner	O
 '	O
listener	O
to	O
intercept	O
because	O
conventional	O
"	O
scanning	O
receivers	O
"	O
are	O
generally	O
only	O
capable	O
of	O
de-modulating	O
conventional	O
analogue	O
modulation	B-Application
schemes	O
such	O
as	O
FM	B-Application
and	O
AM	O
.	O
</s>
<s>
However	O
,	O
some	O
digital	O
wireless	B-Device
microphone	I-Device
systems	O
additionally	O
offer	O
encryption	O
technology	O
in	O
an	O
attempt	O
to	O
prevent	O
more	O
serious	O
'	O
eavesdropping	O
 '	O
which	O
may	O
be	O
of	O
concern	O
for	O
corporate	O
users	O
and	O
those	O
using	O
radio	B-Device
microphones	I-Device
in	O
security	O
sensitive	O
situations	O
.	O
</s>
<s>
Manufacturers	O
currently	O
offering	O
digital	O
wireless	B-Device
microphone	I-Device
systems	O
include	O
AKG-Acoustics	O
,	O
Alteros	O
,	O
Audio-Technica	O
,	O
Lectrosonics	O
,	O
Line	O
6	O
,	O
MIPRO	O
,	O
Shure	O
,	O
Sony	O
,	O
Sennheiser	O
and	O
Zaxcom	O
.	O
</s>
<s>
All	O
are	O
using	O
different	O
digital	O
modulation	B-Application
schemes	O
from	O
each	O
other	O
.	O
</s>
<s>
In	O
the	O
UK	O
,	O
use	O
of	O
wireless	B-Device
microphone	I-Device
systems	O
requires	O
a	O
Wireless	O
Telegraphy	O
Act	O
license	O
,	O
except	O
for	O
the	O
license	O
free	O
bands	O
of	O
173.8	O
–	O
175.0MHz	O
and	O
863	O
–	O
865MHz	O
.	O
</s>
<s>
Licenses	O
are	O
required	O
to	O
use	O
wireless	B-Device
microphones	I-Device
on	O
vacant	O
TV	O
channels	O
in	O
the	O
United	O
States	O
as	O
they	O
are	O
a	O
part	O
of	O
the	O
Broadcast	O
Auxiliary	O
Service	O
(	O
BAS	O
)	O
.	O
</s>
<s>
There	O
are	O
currently	O
some	O
wireless	B-Device
microphone	I-Device
manufacturers	O
that	O
are	O
marketing	O
wireless	B-Device
microphones	I-Device
for	O
use	O
in	O
the	O
United	O
States	O
that	O
operate	O
within	O
the	O
944	O
–	O
952MHz	O
band	O
reserved	O
for	O
studio-transmitter	O
link	O
communications	O
.	O
</s>
<s>
Beginning	O
in	O
2017	O
,	O
the	O
amount	O
of	O
TV	O
band	O
spectrum	O
available	O
for	O
wireless	B-Device
microphone	I-Device
use	O
is	O
decreasing	O
as	O
a	O
result	O
of	O
the	O
incentive	O
auction	O
,	O
which	O
was	O
completed	O
on	O
April	O
13	O
,	O
2017	O
.	O
</s>
<s>
In	O
Australia	O
,	O
operation	O
of	O
wireless	B-Device
microphones	I-Device
of	O
up	O
to	O
100mW	O
EIRP	O
between	O
520MHz	O
and	O
694MHz	O
is	O
on	O
unused	O
television	O
channels	O
and	O
is	O
covered	O
by	O
a	O
class	O
license	O
,	O
allowing	O
any	O
user	O
to	O
operate	O
the	O
devices	O
without	O
obtaining	O
an	O
individual	O
license	O
.	O
</s>
<s>
In	O
many	O
other	O
countries	O
wireless	B-Device
microphone	I-Device
use	O
does	O
require	O
a	O
license	O
.	O
</s>
<s>
Some	O
governments	O
regard	O
all	O
radio	O
frequencies	O
as	O
military	O
assets	O
and	O
the	O
use	O
of	O
unlicensed	O
radio	O
transmitters	O
,	O
even	O
wireless	B-Device
microphones	I-Device
,	O
may	O
be	O
severely	O
punished	O
.	O
</s>
<s>
Broadcasters	O
,	O
theaters	O
,	O
and	O
wireless	B-Device
microphone	I-Device
manufacturers	O
were	O
firmly	O
against	O
these	O
types	O
of	O
devices	O
ostensibly	O
for	O
this	O
reason	O
.	O
</s>
<s>
The	O
outcome	O
of	O
this	O
consultation	O
and	O
the	O
related	O
WSD	O
activities	O
in	O
the	O
US	O
could	O
have	O
far	O
reaching	O
implications	O
for	O
users	O
of	O
UHF	O
radio	B-Device
microphones	I-Device
in	O
the	O
UK	O
and	O
around	O
the	O
world	O
.	O
</s>
