Application
Mode
1
Military IFF
2
Military IFF
3/A
Common (ATC)
4
Military IFF
5
Military IFF
B
Civil (ATC)
C
Civil (Altitude)
D
Civil (unassigned)
Table 5-7 -- Application modes
Direct Altitude and Identity Readout System
Besides receiving altitude information from transponder-equipped aircraft, the DAIR
equipment presents digitally derived synthetic display markers and numerical data
blocks. These blocks do not fade from the scope as do primary RADAR targets. The
data block displayed adjacent to the center mark (aircraft s actual position) consists of
the beacon code that the aircraft is squawking and the altitude at which the aircraft is
flying. Altitude is indicated in 100-foot increments from MSL.
Altitude data is received through mode C interrogations to aircraft transponders.
Interrogations can be filtered to display only aircraft targets within controller-selected
altitude levels.
Traffic Alert and Collision Avoidance System
Traffic Alert and Collision Avoidance System (TCAS) is an airborne collision avoidance
system based on RADAR beacon signals that operates independent of ground-based
equipment. Currently, two versions exist:
TCAS I Provides proximity warnings only to assist the pilot in the visual
acquisition of conflicting aircraft. No recommended avoidance maneuvers are
provided.
5-43