Modbus
Cellular
Gateway
Index
skipping
is
used
to
reserve
slots
for
new
function
insertion,
when
required.
355
7.1.3
USSD
Unstructured
Supplementary
Service
Data
(USSD)
is
a
protocol
used
by
GSM
cellular
telephones
to
communicate
with
the
service
provider's
computers.
USSD
can
be
used
for
WAP
browsing,
prepaid
callback
service,
mobile
‐
money
services,
location
‐
based
content
services,
menu
‐
based
information
services,
and
as
part
of
configuring
the
phone
on
the
network.
14
An
USSD
messageis
up
to
182
alphanumeric
characters
in
length.
Unlike
Short
Message
Service
(SMS)
messages,
USSD
messages
create
a
real
‐
time
connection
during
an
USSD
session.
The
connection
remains
open,
allowing
a
two
‐
way
exchange
of
a
sequence
of
data.
This
makes
USSD
more
responsive
than
services
that
use
SMS.
1
In
"USSD"
page,
there
are
four
windows
for
the
USSD
function.
The
"Configuration"
window
can
let
you
specify
which
3G/4G
module
(physical
interface)
is
used
for
the
USSD
function,
and
system
will
show
which
SIM
card
in
the
module
is
the
current
used
one.
The
second
window
is
the
"USSD
Profile
List"
and
it
shows
all
your
defined
USSD
profiles
that
store
pre
‐
commands
for
activating
an
USSD
session.
An
"Add"
button
in
the
window
can
let
you
add
one
new
USSD
profile
and
define
the
command
for
the
profile
in
the
third
window,
the
"USSD
Profile
Configuration".
When
you
want
to
start
