I just Googled around and gathered info.
According to Unstructured Supplementary Services Data (USSD):
Unstructured Supplementary Services
Data (USSD) allows for the
transmission of information via a GSM
network. Contrasting with SMS, it
offers real time connection during a
session. A USSD message can be upto
182 alphanumeric characters in length.
Unstructured Supplementary Service
Data allows interactive services
between a MS and applications hosted
by the Mobile Operator. These messages
are composed of digits and the #, *
keys, and allow users to easily and
quickly get information/access
services from the Operator.
USSD messages are simple to form and
easy to send. User can directly enter
the ussd string and press call to send
the message. A typical USSD message
starts with a * followed by digits
which indicate an action to be
performed or are parameters. Each
group of numbers is separated by a *,
and the message is terminated with a #.
The USSD gateway in turn can interact with external applications
based on the USSD command. This allows
access to number of value added
services via USSD.
- USSD works on all GSM handsets of Phase II or later.
However, if you are writing Java MIDlet on a Nokia device, it does not work.
