Transponder landing system
A transponder landing system (TLS) is an all-weather, precision landing system that uses existing airborne transponder and instrument landing system (ILS) equipment to create a precision approach at a location where an ILS would normally not be available. == Description == Conventional ILS systems broadcast using a number of "single purpose" antennas.
Source: Wikipedia — Transponder landing system (CC BY-SA 4.0)