Transponder code is defined as?

• A. One of 4,096 four-digit discrete codes ATC assigns to distinguish between aircraft
• B. A code used to broadcast weather
• C. A code used to indicate altitude
• D. A code used to identify the aircraft type

Answer: (A)

A transponder code is a four-digit code assigned by air traffic control to identify and distinguish an aircraft on radar. Each digit can be 0 through 7, giving 4,096 possible combinations, so controllers can assign a unique code to every aircraft to track it separately. The pilot enters this code into the transponder, and ATC uses it to display and monitor your aircraft on radar. This code is not used to broadcast weather or to indicate altitude; altitude information can be sent by the transponder as part of Mode C, but that’s a separate function. Some special codes exist for emergencies or lost comms, but the standard purpose is unique identification.