NOTE : The ATC/mode S will be able to provide the Traffic Collision
____
 Avoidance System (TCAS) with the aircraft address.

 **ON A/C 051-099,
 The Air Traffic Control (ATC) system is based on the replies provided by the
 airborne transponders in response to interrogations from the ATC Secondary
 Surveillance Radar (SSR).
 The ground ATC secondary radar uses technics which provide the air traffic
 control with information that cannot be acquired by the primary radar.
 This system serves to distinguish between aircraft and to maintain effective
 ground surveillance of the air traffic.
 The system provides the air traffic controllers with:

 -
Mode A: transmission of aircraft identification (code number)

 -
Mode C: transmission of aircraft barometric altitude

 -
Mode S: selective calling. The ATC/Mode S transponder receives interrogations from: . Mode S and SSR ground stations . TCAS-equipped aircraft (the Mode S transponder transmits TCAS data from another TCAS-equipped aircraft to its own TCAS computer if installed).

 1EFF : ALL 1 34-52-00Page 1 1 1 Aug 01/05 1 1 1CES 1 Additional to earlier Air Traffic Control Radar Beacon System (ATCRBS) transponders, the Mode S transponder is capable of providing enhanced surveillance (capability to send and receive data link messages). The minimum data link transponder supports all surveillance functions, in addition to bidirectional air-to-air data exchange, ground-to-air data uplink (COMM A), air-to-ground data dowlink (COMM B), and multisite message protocol. In addition, the transponder is capable of receiving Extended Length Messages (ELMs) from the ground. ELMs are received in the COMM C format. ELM transmittals to the ground use the COMM D format.

 NOTE : The ATC is a level 4 transponder.
____ The transponder is capable of processing COMM A/B/C/D data link messages and can be interfaced to an external Mode S Airborne Data Link Processor (ADLP). The transponder has the ability to be upgraded to a level 5 transponder with an internal ADLP function.
 Each (ATC Mode S-equipped) aircraft has its own Mode S address. This address (24-bit) is included in all Mode S transmissions, so that every interrogation can be directed to a specific aircraft, preventing multiple replies. Also, answers are unequivocal from only one specific aircraft. If the discrete address is included in an interrogation, the discrete address is also a part of the reply. This is especially important for use in conjunction with TCAS. For SSR interrogations, the transponder transmits the selectable code number (Mode A) or the barometric altitude (Mode C) if required. For SSR/Mode S all call interrogations, the transponder transmits the same information.
 NOTE : The transponder contains data link capabilities, in addition to Mode
____ S specific services, to function as part of the aircraft telecommunications network. The transponder has the capability of interfacing to a Global Positioning System (GPS) to provide differential GPS operation. The transponder is designed with upgrade-ability to meet future requirements which result from Future Air Navigation System (FANS) and aircraft telecommunication network definitions and enhancements.

R **ON A/C 106-149, 221-299, 301-399, 401-499,
 The Air Traffic Control (ATC) system is based on the replies provided by the airborne transponders in response to interrogations from the ATC Secondary Surveillance Radar (SSR). The ground ATC secondary radar uses technics which provide the air traffic control with information that cannot be acquired by the primary radar.
R 1EFF : 051-099, 106-149, 221-299, 301-399, 1 34-52-00Page 2 1401-499, 1Aug 01/05 1 1 1CES 1

 This system serves to distinguish between aircraft and to maintain effective
 ground surveillance of the air traffic.
 The system provides the air traffic controllers with :

 -
Mode A: transmission of aircraft identification (code number)

 -
Mode C: transmission of aircraft barometric altitude

 -
Mode S: aircraft selective calling and transmission of flight data for the ground surveillance. The mode S is fully compatible with the other modes, A and C. The mode S has been designed as an evolutionary addition to the ATC system to provide the enhanced surveillance and communication capability required for air traffic control automation. Each (ATC Mode S-equipped) aircraft has its own Mode S address. This address (24-bit) is included in all Mode S transmissions, so that every interrogation can be directed to a specific aircraft, preventing multiple replies. Also, answers are unequivocal from only one specific aircraft. If the discrete address is included in an interrogation, the discrete address is also a part of the reply. This is especially important for use in conjunction with TCAS.
　
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