The Transponder Landing System (TLS) uses transponders installed near runways to provide lateral and vertical guidance during landing. TLS calculates the aircraft's position and transmits steering commands to guide the pilot to the runway centerline and correct altitude for touchdown. This system provides guidance to the runway when visibility is below basic instrument approach minimums.

1. Transponder Landing
System (TLS)
Doc. JAIRO GAVIRIA O.
Fuente:
http://www.anpc.com/transponder-
landing-system-technology