Mode S

Mode S – The communication protocol used for aircraft to transmit information to secondary surveillance radar (SSR) and other systems via an on-board transponder. This protocol provides aircraft with various functions such as TCAS and ACAS II. With Mode S, aircraft can communicate their unique identification, location, altitude, and flight parameters to ground-based air traffic control systems and other aircraft in the area. In addition to standard identification and communication, Mode S also enables potential enhancements to safety and efficiency, such as collision avoidance and enhanced surveillance capabilities.