Description

The IDENT feature allows the pilot to transmit, with the push of a button, a special pulse that is added to the transponder reply. The SPI (special position identificaion) pulse is only present in the reply if the pilot has activated the IDENT feature.

This pulse is then received by the SSR on the ground and is processed and presented to the air traffic controller, normally as a flashing of all or part of the position indication and associated label. The details may differ depending on the ATC system used. Some examples (not necessarily from a real system) are shown below (a big yellow flashing X behind the IVB996 track symbol, flashing label of DVK1208 and flashing track symbol of DJK0905).

Uses

The transponder Ident feature is used primarily for two purposes: aircraft identification and mitigation in case of communication loss.