users, TLS also provides a Precision Approach Radar (PAR) graphic display of aircraft position compared to the desired approach course in order for a PAR operator to provide talk-down guidance to the pilot. Since the TLS operates using the long range band of SSR (1030/1090 MHz) there is no rain fade such as experienced with a traditional PAR that uses primary radar. For a traditional PAR, the ability to track the aircraft position is dependent on the aircraft radar cross section. TLS is based on transponder multilateration and trilateration and consequently tracks all aircraft that respond to the interrogations. Omnidirectional antenna surveillance coverage of the TLS extends to 100 nautical miles. The TLS functions using airborne equipment that is currently widely used by the aviation industry. TLS uses the existing Mode 3/A/C/S transponder equipment to determine the aircraft's position. It then transmits the correct signal on the same frequencies used for the current ILS system. All the pilot is required to do is wait for clearance from ATC for the TLS approach and then tune an ILS receiver to the appropriate frequency. TLS uses equipment most airplanes already have. Drawbacks The TLS simulates an ILS signal that is specific to one aircraft's location on a given ILS frequency. The system can provide guidance to 4 aircraft simultaneously on discrete frequencies, but only those aircraft properly cleared for a TLS approach will receive proper guidance. Other aircraft that erroneously tune to a TLS frequency without proper clearance will not receive correct guidance. Operationally from the pilot's perspective, this is no different from conventional ILS systems. The TLS does require a human operator to acquire the aircraft at the system display console and instruct the system to provide guidance based on its transponder code, so there is an operational difference from an ATC perspective. Variations The TLS is available in several transportable configurations for rapid deployment in defense or other temporary applications. The entire system can be transported in a standard 20' Conex container which can also be used as the center of operations, or on a single 463L master pallet. The system can be transported by truck, ship, or any suitable transport aircraft such as a C-130 or C-17, and can also be airlifted by helicopter. The transportable systems can be unpacked and installed to full operational capacity in several hours by 2 trained technicians. See also Distance measuring equipment (DME)