<s>
Encryption	O
,	O
for	O
example	O
,	O
is	O
not	O
generally	O
permitted	O
in	O
the	O
Amateur	O
Radio	O
service	O
except	O
for	O
the	O
special	O
purpose	O
of	O
satellite	B-Application
vehicle	O
control	O
uplinks	O
.	O
</s>
<s>
The	O
following	O
is	O
a	O
partial	O
list	O
of	O
the	O
modes	O
of	O
communication	O
used	O
,	O
where	O
the	O
mode	O
includes	O
both	O
modulation	B-Application
types	O
and	O
operating	O
protocols	O
.	O
</s>
<s>
Radio	O
telegraphy	O
,	O
designed	O
for	O
machine-to-machine	O
communication	O
is	O
the	O
direct	O
on	O
/	O
off	O
keying	O
of	O
a	O
continuous	O
wave	O
carrier	O
by	O
Morse	O
code	O
symbols	O
,	O
often	O
called	O
amplitude-shift	O
keying	O
or	O
ASK	O
,	O
may	O
be	O
considered	O
to	O
be	O
an	O
amplitude	B-Device
modulated	I-Device
mode	O
of	O
communications	O
,	O
and	O
is	O
rightfully	O
considered	O
the	O
first	O
digital	O
data	O
mode	O
.	O
</s>
<s>
Although	O
more	O
than	O
140years	O
old	O
,	O
bandwidth-efficient	O
Morse	O
code	O
,	O
originally	O
developed	O
by	O
Samuel	O
Morse	O
and	O
Alfred	O
Vail	O
in	O
the	O
1840s	O
,	O
uses	O
techniques	O
that	O
were	O
not	O
more	O
fully	O
understood	O
until	O
much	O
later	O
under	O
the	O
modern	O
terms	O
of	O
source	B-General_Concept
coding	I-General_Concept
or	O
data	B-General_Concept
compression	I-General_Concept
.	O
</s>
<s>
Alfred	O
Vail	O
intuitively	O
understood	O
efficient	O
code	O
design	O
:	O
The	O
bandwidth-efficiency	O
of	O
Morse	O
code	O
arises	O
because	O
its	O
encodings	O
are	O
variable	O
length	O
,	O
and	O
Vail	O
assigned	O
the	O
shortest	O
encodings	O
to	O
the	O
most-used	O
symbols	O
,	O
and	O
the	O
longest	O
encodings	O
to	O
the	O
least-used	O
symbols	O
.	O
</s>
<s>
Shannon	O
's	O
information	O
theory	O
resulted	O
in	O
similarly	O
efficient	O
data	O
encoding	O
technologies	O
which	O
use	O
bandwidth	B-Algorithm
like	O
Morse	O
code	O
,	O
such	O
as	O
the	O
modern	O
Huffman	B-General_Concept
,	O
Arithmetic	B-Algorithm
,	O
and	O
Lempel-Ziv	B-Algorithm
codes	O
.	O
</s>
<s>
Modulated	B-Application
continuous	O
wave	O
(	O
MCW	O
)	O
is	O
most	O
often	O
used	O
by	O
repeaters	O
for	O
identification	O
.	O
</s>
<s>
Decades	O
after	O
the	O
advent	O
of	O
digital	O
amplitude-shift	O
keying	O
(	O
ASK	O
)	O
of	O
radio	O
carriers	O
by	O
Morse	O
symbols	O
,	O
radio	O
technology	O
evolved	O
several	O
methods	O
of	O
analog	O
modulating	O
radio	O
carriers	O
such	O
as	O
:	O
amplitude	O
,	O
frequency	O
and	O
phase	B-Device
modulation	I-Device
by	O
analog	O
waveforms	O
.	O
</s>
<s>
Uses	O
IMBE	B-Language
or	I-Language
AMBE	I-Language
CODEC	B-General_Concept
over	O
FSK	O
.	O
</s>
<s>
D-STAR	B-Protocol
-	O
Open	O
specification	O
with	O
proprietary	O
vocoder	O
system	O
available	O
from	O
Icom	O
,	O
Kenwood	O
,	O
and	O
FlexRadio	O
Systems	O
.	O
</s>
<s>
Uses	O
AMBE	O
codec	B-General_Concept
over	O
a	O
FSK	O
modulation	B-Application
variant	O
with	O
TDMA	O
.	O
</s>
<s>
NXDN	O
uses	O
FDMA	O
with	O
bandwidths	B-Algorithm
of	O
6.25kHz	O
common	O
.	O
</s>
<s>
Uses	O
AMBE	O
CODEC	B-General_Concept
with	O
C4FM	O
modulation	B-Application
.	O
</s>
<s>
Uses	O
LPCNet	O
Quantiser	O
CODEC	B-General_Concept
with	O
differential	O
or	O
coherent	O
PSK	B-General_Concept
.	O
</s>
<s>
-	O
Another	O
open	O
source	O
digital	O
voice	O
mode	O
based	O
on	O
Codec	B-Algorithm
2	I-Algorithm
.	O
</s>
<s>
Utilizes	O
punctured	B-Error_Name
convolutional	I-Error_Name
coding	I-Error_Name
and	O
quadratic	O
permutation	O
polynomials	O
for	O
error	O
control	O
and	O
bit	O
stream	O
re-ordering	O
.	O
</s>
<s>
Most	O
amateur	O
digital	O
modes	O
are	O
transmitted	O
by	O
inserting	O
audio	O
into	O
the	O
microphone	O
input	O
of	O
a	O
radio	O
and	O
using	O
an	O
analog	O
scheme	O
,	O
such	O
as	O
amplitude	B-Device
modulation	I-Device
(	O
AM	O
)	O
,	O
frequency	B-Application
modulation	I-Application
(	O
FM	B-Application
)	O
,	O
or	O
single-sideband	B-Device
modulation	I-Device
(	O
SSB	O
)	O
.	O
</s>
<s>
D-STAR	B-Protocol
(	O
Digital	O
Data	O
)	O
a	O
high	O
speed	O
(	O
128	O
kbit/s	O
)	O
,	O
data-only	O
mode	O
.	O
</s>
<s>
Phase-shift	B-General_Concept
keying	I-General_Concept
:	O
</s>
<s>
Spread	B-Architecture
spectrum	I-Architecture
,	O
which	O
may	O
be	O
analog	O
or	O
digital	O
in	O
nature	O
,	O
is	O
the	O
spreading	O
of	O
a	O
signal	O
over	O
a	O
wide	O
bandwidth	B-Algorithm
.	O
</s>
<s>
High-speed	B-Application
multimedia	I-Application
radio	I-Application
,	O
networking	O
using	O
802.11	O
protocols	O
.	O
</s>
<s>
Certain	O
procedural	O
activities	O
in	O
amateur	O
radio	O
are	O
also	O
commonly	O
referred	O
to	O
as	O
'	O
modes	O
 '	O
,	O
even	O
though	O
no	O
one	O
specific	O
modulation	B-Application
scheme	O
is	O
used	O
.	O
</s>
<s>
AllStarLink	O
(	O
ASL	O
)	O
connects	O
amateurs	O
and	O
repeaters	O
via	O
the	O
internet	O
using	O
the	O
Asterisk	B-Language
(	O
PBX	O
)	O
IAX	O
VOIP	O
Protocol	O
.	O
</s>
<s>
Automatic	B-Device
link	I-Device
establishment	I-Device
(	O
ALE	O
)	O
is	O
a	O
method	O
of	O
automatically	O
finding	O
a	O
sustainable	O
communications	O
channel	O
on	O
HF	B-Algorithm
.	O
</s>
<s>
Echolink	B-Protocol
connects	O
amateurs	O
and	O
amateur	O
stations	O
via	O
the	O
internet	O
.	O
</s>
