Which component receives the challenge and sends a coded reply in an IFF system?

In an Identification Friend or Foe (IFF) system, the transponder is the key component that receives a challenge signal from a radar system (such as a search radar) and then responds with a coded reply. When the transponder receives the challenge, it processes the request and generates a specific response that identifies the aircraft or object as friendly, thereby distinguishing it from potential threats. This reply usually contains essential information that helps in enhancing situational awareness for air traffic control and military operations.

The operation of a transponder relies on a two-way communication system where it interprets the incoming challenge and sends back a pre-defined code, ensuring that friendly forces can be quickly recognized and verified. This response mechanism is crucial for the effectiveness of IFF systems, as it helps avoid friendly fire incidents and enhances coordination during complex military operations.