TCAS
Computer

ATSU*

FCU*

* Optional Enhanced
ATC/TCAS
Surveillance
Control Panel
Figure 2-8: Transponder architecture

Note 1: The Mode S transponder must receive GPS data in order to broadcast ADS-B data. The GPS source is either a MMR or a GPS-SU. All MMRs installed on AIRBUS aircraft and Honeywell GPS-SU are compliant with ADS-B OUT requirements. Note 2: The Mode S transponder gets pure GPS data via ADIRU. Only hybrid ADIRUs are able to connect to a GPS source. Therefore, Mode S transponders connected to autonomous ADIRU cannot get GPS data for ADS-B transmissions. Mode S transponders connected to autonomous ADIRU always send a NUC = 0
(i.e. integrity is not known as the aircraft position is not based on GPS).
2.7.1. ACSS XS 950
The ACSS XS 950 transponder (P/N 751-7800-10005) is compliant with DO-260 and the European AMC 20-24. The latest version of XS 950 (P/N 751-7800-10100) is compliant with DO-260A Change 2 and the European AMC 20-24. This latter transponder is directly linked to the GPS source in order to improve the ADS-B OUT performances (e.g. latency).
More information is available at http://www.acssonboard.com/.

2.7.2. TRANSPONDER PART OF ACSS T3CAS
The ACSS T3CAS is a further step of integration including:
-
A Mode S transponder capable of ADS-B NRA as per DO-260A Change 2

-
A TCAS II compliant with TCAS II Change 7.1

-An enhanced TAWS module derived from T2CAS TAWS module.
The advantages of this integration are the same as for T2CAS, a step further:
reduced weight, volume, wiring, and power consumption.
The TCAS module and the Mode S transponder module share the same set of
antennas, reducing weight and wirings.

The certification of the T3CAS is expected by end 2009. More information is
available at http://www.acssonboard.com/media/brochures/T3CAS.pdf.

2.7.3. ROCKWELL COLLINS TPR 901
The Rockwell Collins TPR 901 is capable of ADS-B NRA as per DO-260.
More information is available at
http://www.rockwellcollins.com/products/cs/at/avionics-systems/legacy-products/index.html.

2.7.4. HONEYWELL TRA 67A
The Honeywell TRA 67 A is capable of ADS-B NRA as per DO-260.
More information is available at http://www.honeywell.com/sites/aero/TCAS.htm.

2.8. FUTURE SYSTEMS
At the time of writing the brochure, no new transponder is expected on a short term.

3. TRAFFIC SURVEILLANCE
Traffic Collision Avoidance System – TCAS
3.1 Description of ACAS – TCAS 3-3
3.1.1 TCAS Designation 3-4
3.1.2 TCAS Principle 3-4
3.1.2.1 Detection Phase 3-5
　
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