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Chapter
4
4.3
Command
Syntax
Attention
All
commands
must
begin with the
letters
AT.
AT
is
short for
"Attention"
and
is
used
by
the
modem
to automatically
set
the
baud
rate
and
parity,
AT
must be
entered
in
upper
case;
all
other
commands may
be
in either
upper
or
lower
case,
This
command
is
the
signal to
the
modem
that
what
follows
is
a
command.
Line Length
Limits
AT
may
be
followed
by
one
or
more commands. The
commands
wili
be performed
in
the
order
given.
The number
of
commands
given
at
once
is
limited
by
the
line
length,
which cannot exceed
40
characters following
AT*
Control characters
and
spaces are not
counted, but punctuation
marks
such
as
dashes
or
commas
are.
For example,
the syntax of a
command
to
the
modem
is
as
fol-
lows:
AT
<command> <CR>
Command
Terminator
Note
that
<CR>
denotes
carriage return.
This
is
the
command
terminator; the
command
is
not processed
until
a
<CR>
is
entered.
Example:
AT
M2
DT
(408)
767-8900<CR>
In
this
example
there are
two
commands:
the
M
(monitor
speaker)
and
D
(dial).
Notice
that
a space has
been
put
between
the
line
elements. This
is
optional;
the
commands
can be entered
one
right after
the
other.
4-4
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