<s>
AMTOR	B-Device
(	O
Amateur	O
Teleprinting	O
Over	O
Radio	O
)	O
is	O
a	O
type	O
of	O
telecommunications	O
system	O
that	O
consists	O
of	O
two	O
or	O
more	O
electromechanical	O
teleprinters	O
in	O
different	O
locations	O
that	O
send	O
and	O
receive	O
messages	O
to	O
one	O
another	O
.	O
</s>
<s>
AMTOR	B-Device
is	O
a	O
specialized	O
form	O
of	O
RTTY	O
protocol	O
.	O
</s>
<s>
The	O
term	O
is	O
an	O
acronym	O
for	O
Amateur	O
Teleprinting	O
Over	O
Radio	O
and	O
is	O
derived	O
from	O
ITU-R	O
recommendation	O
476-1	O
and	O
is	O
known	O
commercially	O
as	O
SITOR	B-Device
(	O
Simplex	O
Telex	O
Over	O
radio	O
)	O
developed	O
primarily	O
for	O
maritime	O
use	O
in	O
the	O
1970s	O
.	O
</s>
<s>
AMTOR	B-Device
was	O
developed	O
in	O
1978	O
by	O
Peter	O
Martinez	O
,	O
G3PLX	O
,	O
with	O
the	O
first	O
contact	O
taking	O
place	O
in	O
September	O
1978	O
with	O
G3YYD	O
on	O
the	O
2m	O
Amateur	O
band	O
.	O
</s>
<s>
It	O
was	O
developed	O
on	O
homemade	O
Motorola	O
6800-based	O
microcomputers	B-Architecture
in	O
assembler	O
code	O
.	O
</s>
<s>
AMTOR	B-Device
improves	O
on	O
RTTY	O
by	O
incorporating	O
error	B-Error_Name
detection	I-Error_Name
or	O
error	B-Error_Name
correction	I-Error_Name
techniques	O
.	O
</s>
<s>
The	O
protocol	O
remains	O
relatively	O
uncomplicated	O
and	O
AMTOR	B-Device
performs	O
well	O
even	O
in	O
poor	O
and	O
noisy	O
HF	O
conditions	O
.	O
</s>
<s>
AMTOR	B-Device
operates	O
in	O
one	O
of	O
two	O
modes	O
:	O
an	O
error	B-Error_Name
detection	I-Error_Name
mode	O
and	O
an	O
automatic	B-Error_Name
repeat	I-Error_Name
request	I-Error_Name
(	O
ARQ	B-Error_Name
)	O
mode	O
.	O
</s>
<s>
The	O
AMTOR	B-Device
protocol	O
utilizes	O
a	O
7-bit	O
code	O
for	O
each	O
character	O
,	O
with	O
each	O
code-word	O
having	O
four	O
mark	O
and	O
three	O
space	O
bits	O
.	O
</s>
<s>
In	O
error	B-Error_Name
detection	I-Error_Name
mode	O
,	O
the	O
code	O
word	O
will	O
be	O
dropped	O
;	O
in	O
automatic	B-Error_Name
repeat	I-Error_Name
request	I-Error_Name
mode	O
,	O
the	O
receiver	O
requests	O
that	O
the	O
original	O
data	O
be	O
resent	O
.	O
</s>
<s>
AMTOR	B-Device
also	O
supports	O
FEC	B-Error_Name
in	O
which	O
simple	O
bit-errors	O
can	O
be	O
corrected	O
.	O
</s>
<s>
AMTOR	B-Device
utilizes	O
FSK	O
,	O
with	O
a	O
frequency	O
shift	O
of	O
170	O
Hz	O
,	O
and	O
a	O
symbol	O
rate	O
of	O
100	O
Baud	O
.	O
</s>
<s>
AMTOR	B-Device
is	O
rarely	O
used	O
today	O
,	O
as	O
other	O
protocols	O
such	O
as	O
PSK31	B-Device
are	O
becoming	O
favoured	O
by	O
amateur	O
operators	O
for	O
real-time	O
text	O
communications	O
.	O
</s>
<s>
The	O
ARRL	O
has	O
announced	O
that	O
as	O
of	O
August	O
17	O
,	O
2009	O
,	O
it	O
will	O
be	O
dropping	O
AMTOR	B-Device
bulletin	O
service	O
in	O
favor	O
of	O
the	O
more	O
popular	O
MFSK16	B-Device
and	O
PSK31	B-Device
modes	O
.	O
</s>
