What is the main purpose of a transponder in aviation?

The main purpose of a transponder in aviation is to transmit aircraft position and altitude. The transponder is a crucial device that enhances the aircraft's visibility to air traffic control and other aircraft. It automatically responds to radar signals from ground stations, broadcasting information such as the aircraft's unique identifier (Mode S code), altitude, and sometimes other data.

This capability plays a significant role in maintaining situational awareness for both air traffic controllers and nearby aircraft, thereby improving safety in the airspace. While navigation and communication are also important aspects of aviation, they are not the primary functions of the transponder itself. The transponder is specifically designed for the transmission of positional information, which is essential for tracking and collision avoidance.