What is the primary function of a transponder in air traffic control?

What is the primary function of a transponder in air traffic control?

• A. It uses the VHF band to provide altitude information.
• B. It allows ATC to see the aircraft on radar by replying to radar interrogations.
• C. It provides vertical guidance for approach.
• D. It transmits weather data to ground stations.

Answer: (B)

The transponder’s job is to boost the controller’s ability to identify and track aircraft. In air traffic control, secondary radar works by the radar system sending out interrogations and the aircraft’s transponder replying with encoded information such as its identity and altitude. This exchange lets the controller see the aircraft on the radar display with a specific ID and altitude, greatly improving separation and safety. The transponder uses dedicated microwave frequencies, not the VHF band used for voice comms, and it does not provide weather data or approach guidance—those come from other systems.

The transponder’s job is to boost the controller’s ability to identify and track aircraft. In air traffic control, secondary radar works by the radar system sending out interrogations and the aircraft’s transponder replying with encoded information such as its identity and altitude. This exchange lets the controller see the aircraft on the radar display with a specific ID and altitude, greatly improving separation and safety. The transponder uses dedicated microwave frequencies, not the VHF band used for voice comms, and it does not provide weather data or approach guidance—those come from other systems.