<s>
MDC	O
(	O
Motorola	O
Data	O
Communications	O
)	O
,	O
also	O
known	O
as	O
Stat-Alert	O
,	O
MDC-1200	B-Device
and	O
MDC-600	B-Device
,	O
is	O
a	O
Motorola	O
two-way	O
radio	O
low-speed	O
data	O
system	O
using	O
audio	O
frequency	O
shift	O
keying	O
,	O
(	O
AFSK	O
)	O
.	O
</s>
<s>
MDC-600	B-Device
uses	O
a	O
600	O
baud	O
data	O
rate	O
.	O
</s>
<s>
MDC-1200	B-Device
uses	O
a	O
1,200	O
baud	O
data	O
rate	O
.	O
</s>
<s>
In	O
addition	O
to	O
Motorola	O
,	O
at	O
least	O
two	O
other	O
companies	O
make	O
compatible	O
base	O
station	O
decoders	O
for	O
MDC-1200	B-Device
.	O
</s>
<s>
A	O
general	O
option	O
setting	O
for	O
all	O
MDC	O
systems	O
is	O
to	O
enable	O
or	O
disable	O
an	O
acknowledgement	B-Protocol
(	O
ack	B-Protocol
)	O
data	O
packet	O
.	O
</s>
<s>
For	O
example	O
,	O
following	O
a	O
selective	O
call	O
,	O
the	O
called	O
radio	O
replies	O
with	O
an	O
ack	B-Protocol
.	O
</s>
<s>
In	O
computer-aided	O
dispatch	O
,	O
the	O
encoder/decoder	O
may	O
pass	O
the	O
ack	B-Protocol
to	O
the	O
dispatch	O
computer	O
system	O
,	O
flagging	O
the	O
selective	O
call	O
as	O
having	O
been	O
received	O
by	O
the	O
mobile	O
radio	O
or	O
automatically	O
marking	O
the	O
time	O
of	O
call	O
.	O
</s>
<s>
The	O
disadvantage	O
of	O
using	O
an	O
ack	B-Protocol
on	O
busy	O
channels	O
is	O
that	O
more	O
air	O
time	O
is	O
used	O
:	O
roughly	O
double	O
the	O
air	O
time	O
used	O
by	O
the	O
selective	O
call	O
data	O
alone	O
.	O
</s>
<s>
The	O
ack	B-Protocol
packet	O
takes	O
roughly	O
the	O
same	O
amount	O
of	O
air	O
time	O
as	O
the	O
selective	O
call	O
itself	O
.	O
</s>
<s>
Many	O
MDC-1200	B-Device
systems	O
utilize	O
the	O
unit	O
ID	O
option	O
.	O
</s>
<s>
The	O
leading	O
unit	O
ID	O
takes	O
slightly	O
more	O
air	O
time	O
(	O
is	O
longer	O
)	O
than	O
a	O
trailing	O
ID	O
because	O
of	O
a	O
header	O
tone	O
and	O
the	O
need	O
to	O
delay	O
the	O
data	O
burst	O
to	O
allow	O
time	O
for	O
CTCSS	O
decoders	O
and	O
voting	B-Protocol
comparators	I-Protocol
to	O
open	O
an	O
audio	O
path	O
to	O
the	O
decoder	O
.	O
</s>
<s>
The	O
emergency	O
button	O
option	O
designates	O
a	O
button	O
on	O
hand-held	O
or	O
vehicle	O
radios	O
which	O
sends	O
the	O
MDC-1200	B-Device
unit	O
ID	O
with	O
an	O
emergency	O
flag	O
appended	O
.	O
</s>
<s>
The	O
base	O
station	O
may	O
respond	O
to	O
a	O
button	O
press	O
with	O
a	O
voice	O
acknowledgment	B-Protocol
,	O
for	O
example	O
,	O
"	O
Downtown	O
6	O
,	O
available.	O
"	O
</s>
<s>
If	O
the	O
acknowledgment	B-Protocol
packets	O
are	O
enabled	O
,	O
every	O
status	O
button	O
press	O
gets	O
a	O
handshake	O
packet	O
in	O
response	O
from	O
the	O
base	O
station	O
encoder-decoder	O
.	O
</s>
<s>
The	O
radio	O
where	O
a	O
status	O
button	O
was	O
pressed	O
will	O
normally	O
beep	O
to	O
confirm	O
the	O
decoder	O
's	O
ack	B-Protocol
for	O
a	O
status	O
button	O
press	O
.	O
</s>
<s>
The	O
radio	O
will	O
respond	O
with	O
an	O
'	O
ack	B-Protocol
 '	O
if	O
it	O
hears	O
the	O
request	O
containing	O
its	O
individual	O
ID	O
.	O
</s>
<s>
It	O
can	O
also	O
be	O
programmed	O
to	O
perform	O
this	O
acknowledgement	B-Protocol
'	O
silently	O
 '	O
(	O
the	O
radio	O
user	O
never	O
knows	O
that	O
his	O
radio	O
has	O
been	O
'	O
pinged	O
 '	O
)	O
.	O
</s>
<s>
MDC-1200	B-Device
is	O
patented	O
under	O
U.S.	O
patents	O
;	O
;;	O
and	O
.	O
</s>
<s>
During	O
the	O
patent	O
period	O
,	O
Motorola	O
charged	O
heavy	O
licensing	O
fees	O
for	O
the	O
MDC-1200	B-Device
protocol	O
.	O
</s>
<s>
Manufacturers	O
of	O
third-party	O
MDC-1200	B-Device
hardware	O
,	O
including	O
in-radio	O
encoder/decoder	O
modules	O
(	O
as	O
aftermarket	O
add-ons	O
for	O
non-Motorola	O
radios	O
)	O
,	O
display	O
units	O
for	O
dispatch	O
centers	O
,	O
etc	O
.	O
</s>
<s>
While	O
the	O
USPTO	O
still	O
shows	O
them	O
as	O
active	O
patents	O
,	O
a	O
number	O
of	O
other	O
radio	O
manufacturers	O
have	O
begun	O
including	O
MDC-1200	B-Device
support	O
in	O
their	O
products	O
.	O
</s>
<s>
Vertex	O
Standard	O
manufactures	O
OEM	O
add-on	O
boards	O
for	O
their	O
mobile	O
and	O
portable	O
Land	O
Mobile	O
Radios	O
that	O
support	O
MDC-1200	B-Device
ANI	O
(	O
or	O
PTT	O
ID	O
)	O
.	O
</s>
<s>
Icom	O
Incorporated	O
includes	O
built-in	O
MDC-1200	B-Device
features	O
on	O
some	O
of	O
their	O
newer	O
radios	O
including	O
the	O
IC-F3021/4021	O
portables	O
and	O
IC-F1721/1821	O
mobiles	O
,	O
as	O
does	O
Kenwood	O
Electronics	O
.	O
</s>
