Unstructured Supplementary Service Data or as popularly known, (USSD) is a Global System for Mobile (GSM) communication technology that allows users to access various services.
Coming back home these are the codes you dial starting with * and ending with a # for example the USSD to check Econet balance is *125# Telecel *125# and NetOne is *134#. These are created for local network applications for each operator.
The technology allows sending of texts between a mobile phone and an application program in the network. Applications may include prepaid roaming or mobile chatting.
USSD messages are up to 182 alphanumeric characters in length. The technology is more or less similar to Short Messaging Service (SMS), but,unlike SMS, USSD transactions occur during the session only. USSD messages create a real-time connection during a 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, where messages can be sent to a mobile phone and stored for several days if the phone is not activated or within range.
These short codes usually start with * and end with # and can be typed into any mobile network operator cellphone to call up a specific action. Depending on the nature of transactions, USSD sessions are charged from your airtime or billing balance while most of the sessions are free of charge.
How do I use a USSD code?
Dial the code of the USSD service you want to access, for example, *123#, and then press the call button.