Short-term conflict alert (STCA) is an automated warning system for air traffic controllers (ATCO).
It is a ground-based safety net intended to assist the controller in preventing collision between aircraft by generating, in a timely manner, an alert of a potential or actual infringement of separation minima.
[1] ICAO Doc 4444 requires that radar systems should provide for the display of safety-related alerts including the presentation of actual and predicted conflict.
In this case STCA will generate an alarm to inform the air traffic controller about the hazardous situation identifying the conflicting aircraft.
This system alerts pilots to possible conflicts, and suggests remedial actions, in the form of a climb or descent.