In Telecommunication S, the term of transponder can have the following significances:
-
an automatic apparatus which receives, amplifies and retransmet signals on different Fréquence S,
- an automatic apparatus which transmits a message predetermined in answer to a predetermined received signal.
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In Aeronautical, principle
The transponder of a Aéronef is the embarked equipment which allows the secondary Radar S of the stations of Contrôle of the air traffic on the ground to determine the position of the plane in monitored space. It also makes it possible to give information of position to the other planes being in the vicinity (40 nautical miles, 8700 feet with the top or in lower part) if the latter are equipped with the system TCAS.
Operation
The secondary Radar of air control emits a signal of interrogation made up of an impulse coded on frequency 1030 MHz which the transponder answers by another impulse coded on frequency 1090 MHz. The decoded answer appears on the radar screen on the ground in the form of a stud, accompanied by a code octadécimal to four digits. The function ident transponder sends a particular code which reveals in fat the echo associated on the radar screen with the controller.
Standards
ICAO adopted various aeraonautic standards of transponders:
- Transponder Mode a: whose coding includes/understands the identification of the aircraft
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Transponder mode C: whose coding includes/understands in more altitude pressure of the aircraft
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Transponder mode S: (selective, operational in France as of on March 31st, 2007 for the flights IFR and envisaged for 2009 for the Vols at sight) whose coding 112 bits makes it possible the radar to separately question each aircraft. Much more precise (the transmission altitude being made by increments of 25 feet compared with 100 for the mode C) it also allows the transmission of other types of data, like the registration of the plane, its number of flight and the altitude of flight selected by the pilot.
Regulation
ICAO recommends the obligatory use of a transponder for the flights evolving/moving in zone of class D, C, B and has like for the flights IFR carried out in any zone.
In France, the transponder is obligatory aboard aircraft flying inside a Zone of Temporary Restriction (ZRT).
Internal bonds
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