Transponder code

A Transponder Code is a unique four-digit discrete code assigned by Air Traffic Control (ATC) to aircraft for the purpose of identification and differentiation. There are 4,096 possible transponder codes available for ATC to assign, and each code is used to distinguish between different aircraft in the vicinity. Pilots input the assigned transponder code into their aircraft’s transponder, which sends the code along with other information, such as altitude and location, to ATC. This enables ATC to identify the aircraft on their radar screens and to maintain proper separation between different aircraft. In addition to its identification function, a transponder code can also be used by ATC to issue specific instructions or alerts to the aircraft. As such, transponder codes are an essential part of air traffic management and safety.