Which symbol on the TCAS display is used to help identify aircraft on a controller's scope as a transponder signal?

• A. Radar altimeter
• B. Transponder
• C. TCAS
• D. GPS

Answer: (B)

The concept being tested is how a target is identified as using a transponder in radar/TCAS displays. When an aircraft answers radar interrogations with its transponder, the system can attach an identity and altitude data to that target on the controller’s scope. The symbol that represents the transponder status flags aircraft that are SSR-equipped, showing they are being identified via secondary radar rather than just a raw primary echo. This distinction matters because it lets the controller know which targets carry transponder information (identity and altitude) for more accurate tracking. Radar altimeter relates to measuring own aircraft altitude, GPS is for navigation positioning, and TCAS is the traffic awareness system itself; none of those alone indicate that a target is replying with a transponder. Therefore, the symbol for transponder is the correct one.